tag:theconversation.com,2011:/ca/topics/cane-toads-166/articlesCane toads – The Conversation2024-02-14T01:12:59Ztag:theconversation.com,2011:article/2234612024-02-14T01:12:59Z2024-02-14T01:12:59ZA secret war between cane toads and parasitic lungworms is raging across Australia<p>When the first cane toads were brought from South America to Queensland in 1935, many of the parasites that troubled them were left behind. But deep inside the lungs of at least one of those pioneer toads lurked small nematode lungworms.</p>
<p>Almost a century later, the toads are evolving and spreading across the Australian continent. In <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2023.2403">new research</a> published in Proceedings of the Royal Society B, we show that the lungworms too are evolving: for reasons we do not yet understand, worms taken from the toad invasion front in Western Australia are better at infecting toads than their Queensland cousins.</p>
<h2>An eternal arms race</h2>
<p>Nematode lungworms are tiny threadlike creatures that live in the lining of a toad’s lung, suck its blood, and release their eggs through the host’s digestive tract. The larva that hatch in the toad’s droppings lie in wait for a new host to pass by, then penetrate through its skin and migrate through the amphibian’s body to find the lungs and settle into a comfortable life, and begin the cycle anew.</p>
<p>Parasites and their hosts are locked into an eternal arms race. Any characteristic that makes a parasite better at finding a new host, setting up an infection, and defeating the host’s attempts to destroy it, will be favoured by natural selection. </p>
<p>Over generations, parasites get better and better at infecting their hosts. But at the same time, any new trick that enables a host to detect, avoid or repel the parasites is favoured as well. </p>
<p>So it’s a case of parasites evolving to infect, and hosts evolving to defeat that new tactic. Mostly, parasites win because they have so many offspring and each generation is very short. As a result, they can evolve new tricks faster than the host can evolve to fight them. </p>
<h2>The march of the toads</h2>
<p>The co-evolution between hosts and parasites is most in sync among the ones in the same location, because they encounter each other most regularly. A parasite is usually better able to <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1461-0248.2007.01028.x">infect hosts from the local population</a> it encounters regularly than those from a distant population.</p>
<p>But when hosts invade new territory, it can play havoc with the evolutionary matching between local hosts and parasites. </p>
<p>Since cane toads were released into the fields around Cairns in 1935, the toxic amphibians have hopped some 2,500 kilometres westwards and are currently on the doorstep of Broome. And they have <a href="https://www.nature.com/articles/439803a">changed dramatically</a> along the way. </p>
<p>The Queensland toads are homebodies and spend their lives in a small area, often reusing the same shelter night after night. As a result, their populations can build up to high densities. </p>
<p>For a lungworm larva, having lots of toads in a small area, reusing and sharing shelter sites, makes it simple to find a new host. But at the invasion front (currently in Western Australia), <a href="https://www.publish.csiro.au/wr/WR08021">toads are highly mobile</a>, moving over a kilometre per night when conditions permit, and rarely spending two nights in the same place. </p>
<p>At the forefront of the invasion, toads are few and far between. A lungworm larva at the invasion front, waiting in the soil for a toad to pass by, will have <a href="https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/09-0530.1">few opportunities</a> to encounter and infect a new host. </p>
<h2>Lungworms from the invasion front</h2>
<p>When hosts are rare, we expect the parasite will evolve to get better at infecting the ones it does encounter, because it is unlikely to get a second chance.</p>
<p>To understand how this co-evolution is playing out between cane toads and their lungworms, we did some experiments pairing hosts and parasites from different locations in Australia. What would happen when toad and lungworm strains that had been separated by 90 years of invasion were reintroduced to each other?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-toadzilla-a-sign-of-enormous-cane-toads-to-come-its-possible-toads-grow-as-large-as-their-environment-allows-195929">Is 'Toadzilla' a sign of enormous cane toads to come? It's possible – toads grow as large as their environment allows</a>
</strong>
</em>
</p>
<hr>
<p>To study this we collected toads from different locations, bred them in captivity and reared the offspring in the lab under common conditions. We then exposed them to 50 lungworm larvae from a different area of the range, waited four months for infections to develop, then killed the toads and counted how many adult worms had successfully established in their lungs.</p>
<p>As expected, worms from the invasion front were best at infecting toads, not just their local ones. Behind the invasion front, in intermediate and old populations we found that hosts were able to fight their local parasites better than those from distant populations. </p>
<p>While we saw dramatic differences in infection outcomes, we have yet to determine what biochemical mechanisms caused the differences and how changes in genetic variation of host and parasite populations might have shaped them. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/in-the-evolutionary-arms-race-between-cane-toads-and-lungworms-skin-secretions-play-a-surprising-role-163821">In the evolutionary arms race between cane toads and lungworms, skin secretions play a surprising role</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/223461/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lee A Rollins receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Rick Shine receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Greg Brown does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Cane toads are evolving as they spread across Australia. Parasitic lungworms are becoming more infectious to keep up.Greg Brown, Postdoctoral researcher, Macquarie UniversityLee A Rollins, Scientia Associate Professor, UNSW SydneyRick Shine, Professor in Evolutionary Biology, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1975222023-01-19T19:13:25Z2023-01-19T19:13:25ZCould feral animals in Australia become distinct species? It’s possible – and we’re seeing some early signs<figure><img src="https://images.theconversation.com/files/504379/original/file-20230113-18-j2pfl3.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C3914%2C2646&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>You might think evolution is glacially slow. At a species level, that’s true. But evolution happens every time organisms produce offspring. The everyday mixing of genes – combined with mutations – throws up new generations upon which “selection pressure” will act. </p>
<p>This pressure is popularly known as survival of the fittest, where fittest means “best adapted” individuals. Tiger snakes <a href="https://www.abc.net.au/news/2023-01-09/mount-chappell-island-hummocky-tiger-snakes-larger-bigger-heads/101817298">with a mutation</a> for a larger head can eat larger prey. Evolution is the zoomed-out version, where species change – or evolve into new ones, better adapted to the environment they find themselves in. </p>
<p>Evolution acts over millennia. But given the right conditions, it can also work surprisingly rapidly. Australia’s isolation produced our distinctive animals. But until recently in a geological sense, it had no camels, cats, toads and dogs. Now it does. Millions of feral animals, birds and amphibians now call Australia home. And their new home is beginning to change them in turn. </p>
<h2>Can evolution run fast?</h2>
<p>We’ve long thought evolution grinds slowly. But given the right conditions, pressure can bring change much faster. A <a href="https://www.science.org/doi/10.1126/science.abk0853">recent study</a> found evolution acting up to four times faster than previous estimates. On average, species in the study saw an 18.5% increase per generation in their ability to survive and reproduce. This remarkably rapid change suggests many species (not all) may be well able to adapt to rapid environmental changes.</p>
<p>Australia’s feral animal species all arrived through human efforts. Dogs came first through by contact between First Nations peoples and traders from what is now Indonesia. Cats <a href="https://www.abc.net.au/news/2015-12-22/cats-came-to-australia-with-european-settlers/7049308">came next</a>, accompanying European colonists in the 1700s (and maybe earlier). Camels in the 1840s. Cane toads came in the 1930s. That’s to say nothing of deer, horses, goats, pigs, water buffalo, mynahs, foxes and rabbits. </p>
<p>Once here, dogs, camels and cats rapidly gave up domestication, becoming dingoes, feral camels and feral cats. With each generation, these animals have become better adapted to their new environments. They are now evolving in Australia.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/so-you-want-to-cat-proof-a-bettong-how-living-with-predators-could-help-native-species-survive-170450">So you want to cat-proof a bettong: how living with predators could help native species survive</a>
</strong>
</em>
</p>
<hr>
<h2>Dog or dingo?</h2>
<p>The status of the dingo has been <a href="https://www.publish.csiro.au/wr/WR02045">heavily contested</a> and we even argue about what to <a href="https://www.publish.csiro.au/pc/PC18018">call it</a>. Given it can interbreed with domestic dogs, it’s not a <a href="https://meridian.allenpress.com/australian-zoologist/article-abstract/41/3/347/450006/Taxonomy-of-the-Dingo-It-s-an-ancient-dog">separate species</a>. Recent research suggests <a href="https://www.theguardian.com/environment/2022/apr/23/scientists-find-dingoes-genetically-different-from-domestic-dogs-after-decoding-genome">it’s an intermediary</a> between wolves and domestic dogs. Dingoes have been implicated in the <a href="https://www.tandfonline.com/doi/full/10.1080/00438243.2012.646112">thylacine’s extinction</a> on the mainland.</p>
<p>Given the dingo’s closest relative is the <a href="https://www.pnas.org/doi/10.1073/pnas.2007242117">New Guinea singing dog</a>, which howls like a wolf with overtones of whalesong, the dingo may have already evolved away from its ancestors. There’s certainly evidence of <a href="https://www.nature.com/articles/s41467-020-14515-6">unique selection pressures</a> but nowhere near enough to be considered a separate species. Similarly, dingoes tend to have broader heads than domestic dogs and more flexible joints. They don’t woof but howl. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="fraser island dingo" src="https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504375/original/file-20230113-16-xaug0q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The last pure dingo population lives on Fraser Island. Dingoes elsewhere have some degree of interbreeding with domestic dogs.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>An Australian camel?</h2>
<p>It’s a similar story for camels. Australia’s one-humped dromedaries were imported from Afghanistan and Pakistan because of their ability to live in arid environments. It’s no surprise they have thrived. Hundreds of thousands <a href="https://www.bbc.com/travel/article/20180410-the-strange-story-of-australias-wild-camel">now roam</a> the Red Centre. We may now have the largest wild population of dromedaries <a href="https://pestsmart.org.au/toolkits/feral-camels/">in the world</a>. Given their numbers, in time, we may have a uniquely Australian camel. </p>
<p>Though we have a huge population of camels, they have low genetic diversity as they came from a small original population. Low diversity usually means a species is less able to adapt to changes in the environment.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wild-animals-are-evolving-faster-than-anybody-thought-183633">Wild animals are evolving faster than anybody thought</a>
</strong>
</em>
</p>
<hr>
<h2>Cats are getting larger</h2>
<p>Domestication sits lightly on cats, with the difference between a pet cat and a feral just a couple of missed meals. </p>
<p>Cats are one of the most invasive species globally. In Australia, they have done the worst damage, <a href="https://www.abc.net.au/news/2020-05-25/feral-cat-sand-goanna-photo-outback-queensland/12275890">killing everything</a> from native mice to wallabies with abandon and pushing many to the brink of extinction. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1262376991728242691"}"></div></p>
<p>Ferals are getting bigger, with reports of 7 kilogram cats now common, well up from their domestic range of 4–5kg. Tales of panther-like felines may well be huge feral cats. Some <a href="https://www.australiangeographic.com.au/topics/science-environment/2013/06/huge-feral-cats-wreaking-havoc-in-arnhem-land/">have been estimated</a> at 12–15kg. Take the estimated 1.5 metre feral <a href="https://www.theguardian.com/environment/2021/dec/29/tall-tails-why-does-the-myth-of-exotic-big-cats-prowling-the-australian-bush-persist">killed in 2005</a> – double the nose-to-tail length of a domestic cat. </p>
<p>What’s going on? One reason is feral cats aren’t desexed, meaning toms can <a href="https://aridrecovery.org.au/feral-cats/">grow as large</a> as a small dingo. But it also seems selection pressures are favouring larger cats. We don’t know if it’s due to genetic changes or the rich diet of endangered animals. Normally, gigantism – where species grow to larger than usual sizes – is <a href="https://scitechdaily.com/island-gigantism-and-dwarfism-evolutionary-island-rule-confirmed/">associated with islands</a>. Think of the giant Komodo dragon, or of the extinct dodo – in reality, a giant pigeon. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="feral cat kill wallaby" src="https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504378/original/file-20230113-26-j2pfl3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cats can even kill wallabies, as this image shows.</span>
<span class="attribution"><span class="source">Northern Territory Department of Environment and Natural Resources</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Cane toads: phase shifters with longer legs</h2>
<p>In 1935, the infamous cane toad was brought in to eat the cane beetles plaguing sugar plantations. As we know, cane toads soon figured out there was a lot more to eat. Protected by poisonous glands on their back, they have spread across the tropical north to the Kimberley and down the east coast approaching Sydney. </p>
<p>Toads at the front of the invasion have developed longer legs, making faster travel possible. Remarkably, in some shady gorges in the Kimberley, some <a href="https://www.abc.net.au/news/2019-01-22/cane-toads-change-from-nocturnal-to-diurnal-in-kimberley/10732102#:%7E:text=%22Cane%20toads%20across%20most%20of,day%2C%22%20Dr%20Letnic%20said.">have switched</a> from being nocturnal to diurnal. </p>
<h2>Adaptation is under way – but will we actually see new species?</h2>
<p>Consider too Darwin’s <a href="https://theconversation.com/darwins-finches-highlight-the-unity-of-all-life-38039">famous Galápagos finches</a>. On these isolated islands, finches calved off into separate species. Seed-eaters evolved thicker beaks, while the vampire finch evolved to drink blood from larger birds. </p>
<p>So could it happen here? Yes – if conditions are right. Let’s speculate that natural selection keeps pushing feral cats to get larger and larger. </p>
<p>Eventually, these giant cats would see any domestic cats fleeing from farms or homes not as mates – but as prey. Once the gene flow from smaller cats was cut off, the gene pool would be limited – and we would be on track for a new species. Perhaps one day, we will have a uniquely Australian cat alongside our uniquely Australian dog. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/lets-give-feral-cats-their-citizenship-45165">Let's give feral cats their citizenship</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/197522/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Bateman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Feral cats double the size of domestic tabbies. Cane toads with longer legs. And dingoes with flexible joints. ‘Selection pressure’ is at work on introduced animals.Bill Bateman, Associate professor, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1865422022-07-13T01:08:44Z2022-07-13T01:08:44Z‘The ultimate invader’: high-tech tool promises scientists an edge over the cane toad scourge<figure><img src="https://images.theconversation.com/files/473512/original/file-20220712-16-rg0af.jpg?ixlib=rb-1.1.0&rect=14%2C14%2C4854%2C3226&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock </span></span></figcaption></figure><p>Cane toads are <a href="https://www.environment.nsw.gov.au/topics/animals-and-plants/pest-animals-and-weeds/pest-animals/cane-toads">invasive frogs</a> that threaten the survival of several Australian wildlife species. Scientists and conservation managers have long grappled with how to stop the toad’s march across the continent. </p>
<p>That’s where our new research comes in. A <a href="https://link.springer.com/article/10.1007/s10980-022-01468-y">paper</a> just published describes a computer simulation program we developed to help test cane toad management in the virtual world before strategies are rolled out in real life.</p>
<p>The program, structured like a video game, answers questions such as: should toads be hand-caught or trapped? When is the best point in a toad’s lifecycle to eradicate it? And how best to balance effort and cost versus reward?</p>
<p>We hope the program will help guide scientists and conservation managers to get an edge over their poisonous amphibian foe. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/bBBfp3YvW2Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A video narrated by the author explaining how virToad works.</span></figcaption>
</figure>
<h2>The cane toad disaster</h2>
<p>The cane toad is the ultimate invader, <a href="https://theconversation.com/the-toad-we-love-to-hate-11521">spreading</a> up to 50 kilometres a year and breeding <a href="https://researchonline.jcu.edu.au/43718/">explosively</a>.</p>
<p>What makes the cane toad truly devastating is its weapons of environmental destruction — poison packed in specialised skin glands on its shoulders. This weapon can quickly <a href="https://www.journals.uchicago.edu/doi/10.1086/655116">kill</a> native predators that take a bite, such as goannas, quolls, snakes and even <a href="https://www.theguardian.com/world/2013/jul/03/cane-toads-crocodiles-victims">crocodiles</a>.</p>
<p>The cane toad was brought to Australia from Hawaii in 1935 to control beetles that were damaging sugar cane plantations. While the toads had little impact on the beetles, they thrived in the wild. </p>
<p>Cane toads are now <a href="https://www.nma.gov.au/defining-moments/resources/introduction-of-cane-toads">found</a> across Australia’s north and they’re fast creeping <a href="https://www.wwf.org.au/news/news/2019/indigenous-rangers-key-to-cane-toad-battle">southwest</a>. Within a few years, cane toads are expected to reach the <a href="https://theconversation.com/close-100-man-made-lakes-to-stop-cane-toad-spread-study-11353">Kimberley-Pilbara corridor</a>. </p>
<p>There, man-made waterbodies for livestock grazing are likely to provide cane toads with safe passage through arid landscapes and into the Pilbara region – an important refuge for many native species.</p>
<figure class="align-center ">
<img alt="close up of cane toad face" src="https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473514/original/file-20220712-22-c9nzhu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cane toads are found across Australia’s north.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Managing cane toad invasions</h2>
<p>The Kimberley-Pilbara corridor is now a crucial battleground between cane toads and conservation managers. But cane toads must also be suppressed in landscapes where the species is already established. And preventing the toads from invading Australia’s <a href="https://neobiota.pensoft.net/article/34941/">offshore islands</a>, or eradicating them once there, is also imperative. </p>
<p>Achieving all this with limited resources is a struggle. We developed virToad to guide scientists and conservation managers in their decisions. virToad is a free and open-source program that builds on existing literature and models. </p>
<p>Unlike previous models, virToad simulates the vulnerabilities of cane toads at various stages of their lifecycle, and the management strategies that can exploit them. These nuances make virToad’s predictions more useful than previous models.</p>
<p>For example, cane toads need water to breed and rehydrate, so virToad simulates management strategies along freshwater shorelines. These include traps that lure tadpoles, juveniles and adults, by releasing chemical cues, mimicking toad calls or attracting insects (a food source) with UV lights.</p>
<p>virToad also simulates a promising new strategy of releasing chemical pheromones to suppress tadpole development.</p>
<p>virToad players can trial various management strategies, in any Australian landscape and over timescales of days to years. Each can be carried out in isolation or in combination:</p>
<ul>
<li>hand-capturing juvenile and adult toads</li>
<li>building toad-proof fences to keep the animals out of waterbodies</li>
<li>trapping cane toad <a href="https://theconversation.com/great-invaders-poison-could-also-be-its-downfall-7609">tadpoles</a>, <a href="https://theconversation.com/come-hither-how-imitating-mating-males-could-cut-cane-toad-numbers-93484">juveniles and adults</a></li>
<li>releasing chemical <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.6678">tadpole suppressants</a> into waterbodies.</li>
</ul>
<p>By playing around with different strategies, and understanding the effort needed to implement them, virToad allows conservation managers to calculate whether they have the people and budget to deploy a plan on the ground. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-a-waterless-barrier-and-how-could-it-slow-cane-toads-114363">What is a waterless barrier and how could it slow cane toads?</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="cane toad at night on rock" src="https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473513/original/file-20220712-18-cc60xw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cane toads need water to breed and rehydrate.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>So what worked best?</h2>
<p>Our simulations showed some actions worked better than others in managing cane toad invasions. </p>
<p>In the Northern Territory tropics, for example, hand-collecting and trapping juveniles and adults made the most significant and lasting difference. In fact, a daily effort over a year eradicated toads. But this strategy is expensive and labour-intensive. </p>
<p>The simulation showed similar results could be obtained when adults and juveniles were hand-captured or trapped once a week, for a year – that’s 85% less cost and effort than the daily strategy.</p>
<p>Unfortunately, hand-collecting toads for one day a year – as happens with <a href="https://www.sciencedirect.com/science/article/pii/S2351989420304248">community-led toad-busting</a> activities – had no noticeable impact.</p>
<p>Likewise, fencing waterbodies and trapping or chemically suppressing tadpoles had no lasting impact in the NT tropics simulation. But these strategies may be more effective in other environments. For example, fencing waterbodies may be effective in the arid Kimberley-Pilbara corridor, where other water sources are scarce.</p>
<p>In perhaps our most significant finding, small-scale interventions had negligible long-term benefits. Our simulations showed local toad populations re-established a year after any localised strategy was implemented, regardless of its initial success or the effort expended.</p>
<p>This clearly indicates a landscape-scale approach is needed to manage cane toad invasions. And virToad is uniquely well-suited to guide managers on this undertaking.</p>
<p>Of course, our findings are only virtual. While we took steps to validate the realism of our model, real-world data on the impact of various management strategies is needed to confirm our simulated findings.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-indigenous-expertise-improves-science-the-curious-case-of-shy-lizards-and-deadly-cane-toads-113997">How indigenous expertise improves science: the curious case of shy lizards and deadly cane toads</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="cane toads in bucket with people's feet" src="https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473515/original/file-20220712-12-mom4xw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Once-a-year catching efforts have a negligible effect on toad numbers.</span>
<span class="attribution"><span class="source">Tracey Nearmy/AAP</span></span>
</figcaption>
</figure>
<h2>A new arsenal</h2>
<p>We hope virToad gives scientists and conservation managers a <a href="https://pubmed.ncbi.nlm.nih.gov/29562120/">new arsenal</a> in the fight against cane toads, by helping ensure their decisions are both science-based and cost-effective.</p>
<p>While the design is based on Australian conditions, it can potentially be used in other parts of the world. And as the biodiversity crisis worsens globally, we hope virToad will inspire research into ways of managing other damaging invasive species.</p>
<p>We also plan to further develop virToad into a computer simulation “game” that the general public can play. Through this, we hope to spread the word that effectively fighting cane toads is vital to saving threatened wildlife.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/pest-plants-and-animals-cost-australia-around-25-billion-a-year-and-it-will-get-worse-164969">Pest plants and animals cost Australia around $25 billion a year – and it will get worse</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/186542/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The simulation showed catching cane toads once a week involved 85% less cost and effort than other strategies, but was just as effective.Arman Pili, PhD candidate, Monash UniversityDavid Chapple, Associate Professor in Evolutionary and Conservation Ecology, Monash UniversityReid Tingley, Lecturer, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1584032021-08-27T12:30:54Z2021-08-27T12:30:54ZThe invasive emerald ash borer has destroyed millions of trees – scientists aim to control it with tiny parasitic wasps<figure><img src="https://images.theconversation.com/files/417871/original/file-20210825-15-1ja4r42.jpg?ixlib=rb-1.1.0&rect=25%2C0%2C4255%2C2843&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Emerald ash borer larva cut these feeding galleries on the trunk of a dead ash tree in Michigan. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/emerald-ash-borer-traces-on-a-dead-tree-trunk-royalty-free-image/157602074">corfoto via Getty Images</a></span></figcaption></figure><p>The emerald ash borer (<em>Agrilus planipennis</em>) is a deceptively attractive metallic-green adult beetle with a red abdomen. But few people ever actually see the insect itself – just the trail of destruction it leaves behind under the bark of ash trees. </p>
<p>These insects, which are native to Asia and Russia, were first discovered in Michigan in 2002. Since then they have spread to 35 states and become the <a href="https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-and-diseases/emerald-ash-borer">most destructive and costly invasive wood-boring insect</a> in U.S. history. They have also been detected in the Canadian provinces of <a href="https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/invasive-insects/emerald-ash-borer/">Ontario, Quebec, Manitoba, New Brunswick and Nova Scotia</a>. </p>
<p>In 2021 the U.S. Department of Agriculture <a href="https://www.federalregister.gov/documents/2020/12/15/2020-26734/removal-of-emerald-ash-borer-domestic-quarantine-regulations">stopped regulating the movement of ash trees and wood products in infested areas</a> because the beetles <a href="https://youtu.be/VYMsSefX-qc">spread rapidly despite quarantine efforts</a>. Now federal regulators and researchers are pursuing a different strategy: biological control. Scientists think that <a href="https://www.nrs.fs.fed.us/disturbance/invasive_species/eab/control_management/biological_control/">tiny parasitic wasps</a>, which prey on emerald ash borers in their native range, hold the key to curbing this invasive species and returning ash trees to North American forests. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Metallic green beetle." src="https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1042&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1042&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1042&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1309&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1309&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417872/original/file-20210825-23-1khh9n5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1309&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Adult emerald ash borer beetles are about 0.5 inches long (photo not to scale).</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Emerald_ash_borer#/media/File:Agrilus_planipennis_001.jpg">PA DEC</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p><a href="https://biology.richmond.edu/faculty/kgrayson/">I study invasive forest insects</a> and work with the USDA to develop easier ways of raising emerald ash borers and other invasive insects in research laboratories. This work is critical for discovering and testing ways to better manage forest recovery and prevent future outbreaks. But while the emerald ash borer has spread uncontrollably in nature, producing a consistent laboratory supply of these insects is surprisingly challenging – and developing an effective biological control program requires a lot of target insects.</p>
<h2>The value of ash trees</h2>
<p>Researchers believe the emerald ash borer likely arrived in the U.S. on imported wood packaging material from Asia sometime in the 1990s. The insects lay eggs in the bark crevices of ash trees; when larvae hatch, they tunnel through the bark and feed on the inner layer of the tree. Their impact becomes apparent when the bark is peeled back, revealing dramatic feeding tracks. These channels damage the trees’ <a href="https://www.britannica.com/science/vascular-tissue">vascular tissue</a> – internal networks that transport water and nutrients – and ultimately kill the tree. </p>
<p>Before this invasive pest appeared on the scene, ash trees were particularly popular for residential developments, representing 20-40% of planted trees in some Midwestern communities. Emerald ash borers have killed tens of millions of U.S. trees with an estimated replacement cost of US$10-25 billion. </p>
<p>Ash wood is also <a href="http://www.hardwooddistributors.org/postings/ash-lumber-and-the-emerald-ash-borer">popular for lumber</a> used in furniture, sports equipment and paper, among many other products. The ash timber industry produces <a href="https://www.aphis.usda.gov/import_export/plants/manuals/domestic/downloads/eab-manual.pdf">over 100 million board feet annually, valued at over $25 billion</a>. </p>
<h2>Why quarantines have failed</h2>
<p>State and federal agencies have used quarantines to combat the spread of several invasive forest insects, including <a href="https://www.aphis.usda.gov/aphis/resources/pests-diseases/hungry-pests/the-threat/asian-longhorned-beetle/asian-longhorned-beetle">Asian longhorned beetles</a> and <a href="https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-and-diseases/gypsy-moth/ct_gypsy_moth"><em>Lymantria dispar</em></a>, <a href="https://www.entsoc.org/better-common-names-project">previously known as gypsy moth</a>. This approach seeks to reduce the movement of eggs and young insects hidden in lumber, nursery plants and other wood products. In counties where an invasive species is detected, regulations typically require wood products to be heat-treated, stripped of bark, fumigated or chipped before they can be moved. </p>
<p>The federal emerald ash borer quarantine started with 13 counties in Michigan in 2003 and increased exponentially over time to cover than a quarter of the continental U.S. Quarantines can be effective when forest insect pests mainly spread through movement of their eggs, hitchhiking long distances when humans transport wood. </p>
<p>However, female emerald ash borers <a href="https://www.federalregister.gov/documents/2020/12/15/2020-26734/removal-of-emerald-ash-borer-domestic-quarantine-regulations">can fly up to 12 miles per day for as long as six weeks after mating</a>. The beetles also are difficult to trap, and typically are not detected until they have been present for three to five years – too late for quarantines to work. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing range of ash trees and counties where emerald ash borer has been detected." src="https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417874/original/file-20210825-23-1ukonjt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The emerald ash borer has been detected throughout much of the range of ash trees in the U.S.</span>
<span class="attribution"><a class="source" href="https://www.aphis.usda.gov/plant_health/plant_pest_info/emerald_ash_b/downloads/eab-ash-range-map.pdf">USDA</a></span>
</figcaption>
</figure>
<h2>Next option: Wasps</h2>
<p>Any biocontrol plan poses concerns about unintended consequences. One notorious example is the introduction of cane toads in Australia in the 1930s to reduce beetles on sugarcane farms. The toads didn’t eat the beetles, but they spread rapidly and ate lots of other species. And <a href="https://www.environment.gov.au/biodiversity/invasive-species/publications/factsheet-cane-toad-bufo-marinus">their toxins killed predators</a>. </p>
<p>Introducing species for biocontrol is strictly regulated in the U.S. It can take two to 10 years to demonstrate the effectiveness of potential biocontrol agents, and obtaining a permit for field testing can take two more years. Scientists must demonstrate that the released species specializes on the target pest and has minimal impacts on other species.</p>
<p>Four wasp species from China and Russia that are natural enemies of the emerald ash borer have gone through the approval process for field release. These wasps are parasitoids: They deposit their eggs or larvae into or on another insect, which becomes an unsuspecting food source for the growing parasite. Parasitoids are great candidates for biocontrol because they typically exploit a single host species.</p>
<p>The selected wasps are tiny and don’t sting, but their egg-laying organs can penetrate ash tree bark. And they have specialized sensory abilities to find emerald ash borer larva or eggs to serve as their hosts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Ash borer larva and a wasp species that preys on it." src="https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/418053/original/file-20210826-23-se9m77.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An emerald ash borer larva in wood (left); <em>Tetrastichus planipennisi</em>, a parasitic wasp that preys on ash borers; and wasp larva that have grown and eaten the ash borer.</span>
<span class="attribution"><span class="source">USDA</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The USDA is working to rear massive numbers of parasitoid wasps in lab facilities by providing lab-grown emerald ash borers as hosts for their eggs. Despite COVID-19 disruptions, the agency produced over 550,000 parasitoids in 2020 and released them at over 240 sites.</p>
<p>The goal is to create self-sustaining field populations of parasitoids that reduce emerald ash borer populations in nature enough to allow replanted ash trees to grow and thrive. Several studies have shown <a href="https://www.fs.fed.us/nrs/pubs/jrnl/2015/nrs_2015_bauer_001.pdf">encouraging early results</a>, but securing a future for ash trees will require more time and research. </p>
<p>One hurdle is that emerald ash borers grown in the lab need fresh ash logs and leaves to complete their life cycle. I’m part of a team working to develop an alternative to the time- and cost-intensive process of collecting logs: an artificial diet that the beetle larvae can eat in the lab. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416540/original/file-20210817-15-sq9zae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fresh cut ash logs await processing to collect newly emerging emerald ash borer adults, which will lay eggs for the laboratory colony.</span>
<span class="attribution"><a class="source" href="https://drive.google.com/drive/folders/1gayeW50DEK6sQ6-zahQIRkIMbrhfO3Hi">Anson Eaglin/USDA</a></span>
</figcaption>
</figure>
<p>The food must provide the right texture and nutrition. Other leaf-feeding insects readily eat artificial diets made from wheat germ, but species whose larvae digest wood are pickier. In the wild, emerald ash borers only feed on species of ash tree.</p>
<p>In today’s global economy, with people and products moving rapidly around the world, it can be hard to find effective management options when invasive species become established over a large area. But lessons learned from the emerald ash borer will help researchers mobilize quickly when the next forest pest arrives.</p>
<p><em>This article has been updated to correct the plural form of larva to larvae.</em></p><img src="https://counter.theconversation.com/content/158403/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kristine Grayson receives cooperative agreement funding from the USDA Animal and Plant Health Inspection Service (APHIS) program for Plant Protection and Quarantine (PPQ). </span></em></p>Biological control strategies curb pests using other species that attack the invader. A biologist explains why it can take more than a decade to develop an effective biological control program.Kristine Grayson, Associate Professor of Biology, University of RichmondLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1649692021-07-29T19:59:09Z2021-07-29T19:59:09ZPest plants and animals cost Australia around $25 billion a year – and it will get worse<figure><img src="https://images.theconversation.com/files/413674/original/file-20210729-23-1xua4jp.jpg?ixlib=rb-1.1.0&rect=63%2C197%2C4185%2C2624&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">AAP</span></span></figcaption></figure><p>Shamefully, Australia has one of the <a href="https://theconversation.com/australias-threatened-species-plan-has-failed-on-several-counts-without-change-more-extinctions-are-assured-163434">highest extinction rates</a> in the world.
And the <a href="https://theconversation.com/invasive-species-are-australias-number-one-extinction-threat-116809">number one</a> threat to our species is invasive or “alien” plants and animals. </p>
<p>But invasive species don’t just cause extinctions and biodiversity loss – they also create a serious economic burden. Our <a href="http://doi.org/10.3897/neobiota.67.58834">research</a>, published today, reveals invasive species have cost the Australian economy at least A$390 billion in the last 60 years alone. </p>
<p>Our paper – the most detailed assessment of its type ever published in this country – also reveals feral cats are the worst invasive species in terms of total costs, followed by rabbits and fire ants.</p>
<p>Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412797/original/file-20210723-25-6b2d3n.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Feral cats are Australia’s costliest invasive species.</span>
<span class="attribution"><span class="source">Adobe Stock/240188862</span></span>
</figcaption>
</figure>
<h2>Huge economic burden</h2>
<p>Invasive species are those not native to a particular ecosystem. They are introduced either by accident or on purpose and become pests.</p>
<p>Some costs involve direct damage to agriculture, such as insects or fungi destroying fruit. Other examples include measures to control invasive species like feral cats and cane toads, such as paying field staff and buying fuel, ammunition, traps and poisons.</p>
<p>Our previous research put the global cost of invasive species at <a href="https://theconversation.com/attack-of-the-alien-invaders-pest-plants-and-animals-leave-a-frightening-1-7-trillion-bill-158628">A$1.7 trillion</a>. But this is most certainly a gross underestimate because so many data are missing.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/attack-of-the-alien-invaders-pest-plants-and-animals-leave-a-frightening-1-7-trillion-bill-158628">Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill</a>
</strong>
</em>
</p>
<hr>
<p>As a wealthy nation, Australia has accumulated more reliable cost data than most other regions. These costs have increased exponentially over time – up to sixfold each decade since the 1970s.</p>
<p>We found invasive species now cost Australia around A$24.5 billion a year, or an average 1.26% of the nation’s <a href="https://www.abs.gov.au/statistics/economy/key-indicators">gross domestic product</a>. The costs total at least A$390 billion in the past 60 years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412787/original/file-20210723-17-nfqpza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Increase in annual costs of invasive species in Australia from 1960 to 2020. The predicted range for 2020 is shown in the upper left quadrant. Note the logarithmic scale of the vertical axis.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Worst of the worst</h2>
<p>Our analysis found feral cats have been the most economically costly species since 1960. Their A$18.7 billion bill is mainly associated with attempts to control their abundance and access, such as fencing, trapping, baiting and shooting.</p>
<p>Feral cats are a <a href="https://theconversation.com/australia-must-control-its-killer-cat-problem-a-major-new-report-explains-how-but-doesnt-go-far-enough-154931">main driver</a> of extinctions in Australia, and so perhaps investment to limit their damage is worth the price tag.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412799/original/file-20210723-17-1sloenv.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tasmania’s bane — ragwort (<em>Senecio jacobaea</em>)</span>
<span class="attribution"><span class="source">Adobe Stock/157770032</span></span>
</figcaption>
</figure>
<p>As a group, the management and control of invasive plants proved the worst of all, collectively costing about A$200 billion. Of these, <a href="https://www.agric.wa.gov.au/grains-research-development/annual-ryegrass">annual ryegrass</a>, <a href="https://weeds.dpi.nsw.gov.au/Weeds/PartheniumWeed">parthenium</a> and <a href="https://dpipwe.tas.gov.au/invasive-species/weeds/weeds-index/declared-weeds-index/ragwort">ragwort</a> were the costliest culprits because of the great effort needed to eradicate them from croplands.</p>
<p>Invasive mammals were the next biggest burdens, costing Australia A$63 billion.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412655/original/file-20210722-23-4loggw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The 10 costliest invasive species in Australia.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Variation across regions</h2>
<p>For costs that can be attributed to particular states or territories, New South Wales had the highest costs, followed by Western Australia then Victoria.</p>
<p><a href="https://www.daf.qld.gov.au/business-priorities/biosecurity/invasive-plants-animals/ants/fire-ants">Red imported fire ants</a> are the costliest species in Queensland, and ragwort is the economic bane of Tasmania. </p>
<p>The <a href="https://weedsofmelbourne.org/common-heliotrope-or-potato-weed-heliotropium-europaeum">common heliotrope</a> is the costliest species in both South Australia and Victoria, and annual ryegrass tops the list in WA. </p>
<p>In the Northern Territory, the <a href="https://dothideomycetes.org">dothideomycete</a> fungus that causes <a href="https://nt.gov.au/industry/agriculture/food-crops-plants-and-quarantine/banana-freckle">banana freckle disease</a> brings the greatest economic burden, whereas cats and <a href="https://www.environment.nsw.gov.au/topics/animals-and-plants/pest-animals-and-weeds/pest-animals/foxes">foxes</a> are the costliest species in the ACT and NSW.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=545&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=545&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=545&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=684&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=684&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412657/original/file-20210722-19-xptr2z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=684&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The three costliest species by Australian state/territory.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Better assessments needed</h2>
<p>Our study is one of 19 region-specific analyses <a href="https://doi.org/10.3897/neobiota.67.69971">released today</a>. Because the message about invasive species must get out to as many people as possible, our article’s abstract was translated into <a href="http://doi.org/10.3897/neobiota.67.58834">24 languages</a>.</p>
<p>This includes <a href="https://omniglot.com/writing/pitjantjatjara.htm">Pitjantjatjara</a>, <a href="https://www.welcometocountry.org/10-most-widely-spoken-aboriginal-languages-in-australia/">a widely spoken Indigenous language</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-threatened-species-plan-has-failed-on-several-counts-without-change-more-extinctions-are-assured-163434">Australia’s threatened species plan has failed on several counts. Without change, more extinctions are assured</a>
</strong>
</em>
</p>
<hr>
<p>Even the massive costs we reported are an underestimate. This is because of we haven’t yet surveyed all the places these species occur, and there is a lack of standardised reporting by management authorities and other agencies. </p>
<p>For example, our database lists several fungal plant pathogens. But no cost data exist for some of the worst offenders, such as the widespread <em>Phytophthora cinnamomi</em> pathogen that causes major <a href="https://doi.org/10.1071/BT07159">crop losses and damage to biodiversity</a>.</p>
<p>Developing <a href="https://news.microsoft.com/en-au/features/teaming-up-for-turtles/">better methods</a> to estimate the environmental impacts of invasive species, and the benefit of management actions, will allow us to use limited resources more efficiently.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412956/original/file-20210724-27-120ky75.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Phytophthora cinnamomi</em>, a widespread, but largely uncosted, fungal pathogen.</span>
<span class="attribution"><span class="source">Adobe Stock/272252666</span></span>
</figcaption>
</figure>
<h2>A constant threat</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412955/original/file-20210724-15-1dfk65.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fall armyworm, a major crop pest.</span>
<span class="attribution"><span class="source">Adobe Stock/335450066</span></span>
</figcaption>
</figure>
<p>Many species damaging to <a href="https://www.agriculture.gov.au/pests-diseases-weeds/plant/national-priority-plant-pests-2019">agriculture</a> and the <a href="https://www.agriculture.gov.au/biosecurity/environmental/priority-list">environment</a> are yet to make it to our shores. </p>
<p>The recent arrival in Australia of fall armyworm, <a href="https://www.agriculture.gov.au/pests-diseases-weeds/plant/exotic-armyworm">a major agriculture pest</a>, reminds us how invasive species will <a href="https://doi.org/10.1038/ncomms14435">continue their spread</a> here and elsewhere.</p>
<p>As well as the economic damage, invasive species also bring <a href="https://doi.org/10.1038/ncomms12986">intangible costs</a> we have yet to measure adequately. These include the true extent of ecological damage, human health consequences, erosion of ecosystem services and the loss of cultural values.</p>
<p>Without better data, increased investment, a stronger biosecurity system and interventions such as animal culls, invasive species will continue to wreak havoc across Australia.</p>
<hr>
<p><em>The authors acknowledge the Traditional Owners of the lands on which they did this research.</em></p>
<p><em>Ngadlu tampinthi yalaka ngadlu Kaurna yartangka inparrinthi. Ngadludlu tampinthi, parnaku tuwila yartangka</em>.</p><img src="https://counter.theconversation.com/content/164969/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corey J. A. Bradshaw receives funding from Australian Research Council. </span></em></p><p class="fine-print"><em><span>Andrew Hoskins receives funding from the Department of Agriculture, Water and the Environment. </span></em></p>Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityAndrew Hoskins, Research scientist CSIRO Health and Biosecurity, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1638212021-07-18T20:03:14Z2021-07-18T20:03:14ZIn the evolutionary arms race between cane toads and lungworms, skin secretions play a surprising role<figure><img src="https://images.theconversation.com/files/409688/original/file-20210705-21-s23dlf.JPG?ixlib=rb-1.1.0&rect=23%2C7%2C5152%2C2894&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Martin Mayer</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Unlike many other species of amphibians, the cane toad is thriving. It was introduced to Australia (and other places, such as Hawaii) to get rid of pest insects in sugar cane plantations. It had no effect on the pest insects, but soon after its introduction in 1935 it began to spread over large parts of the country. </p>
<p>And it didn’t come alone. Cane toads brought with them a parasite from their native range in South America, the lungworm nematode <em>Rhabdias pseudosphaerocephala</em>. </p>
<p>This invasion provides an ideal model to study the evolutionary “arms race” by which hosts and parasites adjust to each other, as we showed in a recent <a href="https://academic.oup.com/biolinnean/article/132/4/861/6126939">study</a>.</p>
<h2>How parasites can drive evolution</h2>
<p>Parasites are the stuff of nightmares (just think of the <a href="https://theconversation.com/meet-phronima-the-barrel-riding-parasite-that-inspired-the-movie-alien-22555">creature</a> in the movie Alien). Most people don’t think about parasites too much, and one reason is that over the past two centuries we humans managed to rid ourselves of most parasites that used to pester us.</p>
<p>Nonetheless, parasites are an essential part of most ecosystems and important drivers of evolution. But for most kinds of parasites, we don’t really know fundamental facts such as how they find their hosts in the first place and conversely, how hosts protect themselves from getting infected. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/meet-phronima-the-barrel-riding-parasite-that-inspired-the-movie-alien-22555">Meet Phronima, the barrel-riding parasite that inspired the movie Alien</a>
</strong>
</em>
</p>
<hr>
<p>The host and its parasites are locked in an “arms race” of adaptations and counter‐adaptations. Hosts evolve to detect and reject parasites; parasites evolve to deceive the host’s detection and suppression systems; then hosts evolve to defeat those new tricks, and so on. </p>
<p>This is why host–parasite interactions can be powerful drivers of evolution. Selection should favour hosts that can either reduce their chances of getting infected, which is called resistance, or limit the harm caused by a given parasite infection, which is called tolerance.</p>
<h2>Cane toads vs lungworms</h2>
<p>How does that arms race play out during a biological invasion, when both the host and the parasite are subject to powerful new evolutionary forces? </p>
<p>Using cane toads and their lungworm parasites, our <a href="https://onlinelibrary.wiley.com/doi/10.1111/ele.13832">new paper</a> shows that the skin secretions of the cane toad host play a surprisingly important role. </p>
<p>The secretions that coat an amphibian consists of two parts: substances produced by the amphibian itself plus skin microbiome, mostly bacteria. These secretions contain many antimicrobial properties, which might help to fight off pathogens (such as chytrid fungus, the cause of so many amphibian declines). </p>
<p>At the same time, parasites try to overcome those barriers. Lungworm larvae (which develop in the faeces of an infected toad and then wait for a new toad to pass by) might use the smell of skin secretions as a cue to find their host in the first place.</p>
<p>We reasoned that the infective larvae of lungworms might even use the toad’s skin secretions to cloak themselves from the amphibians’ immune system when trying to make their way to the lungs (which is where they need to settle, mature, and reproduce). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409689/original/file-20210705-35922-1q2zn86.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The cane toads’ current distribution in Australia (a), a cane toad used for our experiments (b) and a lungworm parasite located in a toads’ lung (c).</span>
<span class="attribution"><span class="source">Mayer, Shine & Brown</span></span>
</figcaption>
</figure>
<h2>How the role of skin secretions changes</h2>
<p>If hosts and parasites are constantly adapting to each other, we expect to see different strategies in different places for infection avoidance (in hosts) and host detection (in parasites). These differences might arise very quickly, such as during a biological invasion. </p>
<p>To test this idea, we experimentally infected cane toads from different regions in Australia with lungworm parasites from different regions. Additionally, we reduced skin secretions in some of the toads to test how their presence or absence affected the infection success of the parasite. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409687/original/file-20210705-35723-jaq4xj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A male cane toad in Northern Australia.</span>
<span class="attribution"><span class="source">Martin Mayer</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We found that the role of skin secretions differed markedly between geographic regions. </p>
<p>In the toads’ core range (their main habitat) in tropical Queensland, toad skin secretions functioned as a cue for the parasite to find their host. But not only that, they also helped the parasites to infect the toads, meaning that more parasites managed to reach the toads’ lungs when skin secretions were intact. So it seems that these lungworms indeed cloak themselves from the host’s immune system. </p>
<p>But this was not the case at the toads’ invasion front (where toads are spreading into new territory) in Western Australia. Here, the skin secretions of cane toads appear to act as a <em>defence</em> against lungworms, reducing rather than enhancing their infection success. </p>
<p>Thus, although cane toads have been spreading through Australia for only 85 years, we see major divergences in the roles that their skin secretions play in host–parasite biology. </p>
<h2>The state of the arms race</h2>
<p>These geographical divergences fit well with the idea that cane toads in the core range have low resistance to parasite infection, because parasites are ubiquitous due to the nice warm and wet conditions year round. </p>
<p>Conversely, at the invasion‐front, where conditions are harsh and dry for most of the year, increased host resistance might be favoured – especially if parasite infection reduces the dispersal ability of a fast-moving invasion-front toad. </p>
<p>Thus, the cane toads on the invasion-front appear to be ahead in the arms race: they have adapted to the new conditions, while the lungworms are still catching up.</p><img src="https://counter.theconversation.com/content/163821/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Shine receives funding from the Australian Research Council. There is no conflict of interest.</span></em></p><p class="fine-print"><em><span>Martin Mayer does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Australia’s invasive cane toads may be out-evolving their lungworm parasites.Martin Mayer, Postdoctoral Research Associate in Animal Ecology, Aarhus UniversityRick Shine, Professor in Evolutionary Biology, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1239862019-09-23T06:46:47Z2019-09-23T06:46:47ZEat your heart out: native water rats have worked out how to safely eat cane toads<figure><img src="https://images.theconversation.com/files/293504/original/file-20190923-23792-1hnh33u.JPG?ixlib=rb-1.1.0&rect=87%2C43%2C3171%2C2399&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Water rats in Western Australia are safely hunting cane toads.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>Australia’s water rats, or Rakali, are one of Australia’s beautiful but lesser-known native rodents. And these intelligent, semi-aquatic rats have revealed another talent: they are one of the only Australian mammals to safely eat toxic cane toads.</p>
<p>Our research, <a href="https://www.publish.csiro.au/AM/AM19016">published today</a> in Australian Mammalogy, found water rats in Western Australia adapted to hunt the highly poisonous toads less than two years after the toads moved into the rats’ territory. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/weve-cracked-the-cane-toad-genome-and-that-could-help-put-the-brakes-on-its-invasion-103362">We've cracked the cane toad genome, and that could help put the brakes on its invasion</a>
</strong>
</em>
</p>
<hr>
<p>The rats, which can grow to over 1kg, are the only mammal found to specifically target large toads, neatly dissecting the toads to eat their hearts and livers while avoiding the poisonous skin and glands.</p>
<h2>Water rats</h2>
<p><a href="https://www.australiangeographic.com.au/topics/wildlife/2018/02/meet-the-rakali-australias-otter-equivalent/">Water rats</a> are nocturnal and specially adapted to live in waterways, with webbed feet and soft water-resistant fur. Their fur is so impressive there was once a thriving water rat fur industry in Australia.</p>
<p>They can be found in lakes, rivers and estuaries, often living alongside people, in New South Wales, Queensland, Tasmania, South Australia, far north and southwest Western Australia, the Northern Territory, and Victoria, where they can even be seen along St Kilda Pier. </p>
<p>Water rats are also highly intelligent, as shown by their rapid adaptation to hunting and eating one of Australia’s most toxic introduced species – the invasive cane toad.</p>
<p>Cane toads were introduced to Australia in 1935 in an ill-fated attempt to control the cane beetle. They have <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2014.1385">spread across the north of the country</a> at up to 60km per year, leaving devastation in their wake. Many native species, such as <a href="https://www.publish.csiro.au/wr/WR09125">northern quolls</a>, <a href="https://www.publish.csiro.au/wr/WR05042">yellow-spotted monitors</a>, and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0006320708001511">crocodiles</a>, have suffered widespread declines, and in some cases local extinctions, as a result of eating cane toads. </p>
<p>The toads secrete a toxin in their parotoid glands (on the back, neck and shoulders) that can be fatal even in very small doses. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/293506/original/file-20190923-23770-k2rlzx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A cane toad at our field site in the Kimberley.</span>
<span class="attribution"><span class="source">Marissa Parrott</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Eat your heart out</h2>
<p>Cane toads arrived at our <a href="http://projectkimberley.org/">field site</a> in the Kimberley, Western Australia, in 2011-12, leading to a crash in the populations of predators including numerous lizards and northern quolls.</p>
<p>However, in 2014 we found a creek dotted with the bodies of cane toads that had clearly been attacked. Every morning we discovered up to five new dead toads with small, near-identical incisions down their chest in just a five-metre stretch of creek. What was using almost surgical precision to attack these toads? </p>
<p>Post-mortem analysis showed that in larger toads the heart and liver had been removed, and the gall bladder (which contains toxic bile salts) neatly moved outside the chest cavity. In medium-sized toads, besides the removal of the heart and liver, one or both back legs had been stripped of their toxic skin and the muscle also eaten. </p>
<p>The finding intrigued us enough to dissect waterlogged and rotting toad bodies in 40°C heat. Using remote infrared camera footage and analysis of the bites left on the muscle, we found our clever attacker – the native water rat!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/293507/original/file-20190923-23806-1fccins.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A water rat caught on camera hunting for cane toads in the Kimberley.</span>
<span class="attribution"><span class="source">Marissa Parrott</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>What kind of toads are rats eating?</h2>
<p>While there have been anecdotal reports of water rats eating toads in Queensland and the Northern Territory, there were no published reports of this in Western Australia, where the toad was a more recent arrival. </p>
<p>We also didn’t know whether rats could tolerate the toad toxins, or were targeting non-toxic parts of the body. And we wanted to find out whether the rats were targeting small (and less toxic) toads, as <a href="https://opus.lib.uts.edu.au/bitstream/10453/36786/1/Cabrera_Guzman_Rodents_Toads_Etal2014.pdf">some other rodent species</a> do, or were deliberately going after larger toads which are a better source of food.</p>
<p>During our study we captured and measured more than 1,800 cane toads in just 15 days in the vicinity of the water rats’ creek. The vast majority, 94%, were medium-sized; 3.5% were small (less than 4cm long); and just 2.5% were large (greater than 10cm long).</p>
<p>But despite medium toads being far more common, three quarters of the <em>dead</em> toads we found were large, and the remainder were medium. No small toad bodies were found or observed being attacked.</p>
<p>While some species, such as keelback snakes and several birds (including <a href="https://link.springer.com/article/10.1007/s10530-010-9903-8">black and whistling kites</a>, and crows) can eat cane toads, there has been less evidence of mammals hunting this new type of prey and living to tell the tale. </p>
<p>Some rodents can eat small juvenile toads, but no rodents have been documented specifically targeting large toads. In our case, water rats preferred to eat large toads, despite medium-sized toads outnumbering them by 27 to 1.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/293508/original/file-20190923-23801-bior0a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A water rat eating at Healesville Sanctuary.</span>
</figcaption>
</figure>
<p>We’re not sure whether water rats have very rapidly learned how to safely attack and eat cane toads, or if they are adapting a similar long-term hunting strategy that they may use to eat toxic native frogs. </p>
<p>Water rats are very well placed to pass on hunting strategies, as they care for their offspring for at least four weeks after they finish producing milk. This could help spread the knowledge of toad hunting across streams and creeks over time. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-economics-of-cash-for-cane-toads-a-textbook-example-of-perverse-incentives-109574">The economics of 'cash for cane toads' – a textbook example of perverse incentives</a>
</strong>
</em>
</p>
<hr>
<p>While this behaviour seems to be confined to local populations, if these tactics spread, water rats may be able to suppress toad populations when they reach water bodies – another small line of defence against this toxic killer.</p><img src="https://counter.theconversation.com/content/123986/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marissa Parrott is affiliated with Zoos Victoria, a zoo-based conservation organisation fighting extinction for some of the world's most endangered species.</span></em></p><p class="fine-print"><em><span>Sean Doody and Simon Clulow do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When neatly dissected cane toad corpses began turning up next to a creek in the Kimberley, scientists went on the hunt for the clever killer.Marissa Parrott, Reproductive Biologist, Wildlife Conservation & Science, Zoos Victoria, and Honorary Research Associate, BioSciences, The University of MelbourneSean Doody, Conjoint Fellow, University of NewcastleSimon Clulow, MQ Research Fellow, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1168092019-05-09T20:05:58Z2019-05-09T20:05:58ZInvasive species are Australia’s number-one extinction threat<figure><img src="https://images.theconversation.com/files/273482/original/file-20190509-183103-1a0nmhj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Barking Owls are one of Australia’s 1,770 threatened or endangered species.
</span> <span class="attribution"><span class="source">Navin/Flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>This week many people across the world stopped and stared as extreme headlines announced that one eighth of the world’s species – more than a million – are threatened with extinction.</p>
<p>According to the <a href="https://www.ipbes.net/sites/default/files/downloads/spm_unedited_advance_for_posting_htn.pdf">UN report</a> from the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services (IPBES) which brought this situation to public attention, this startling number is a consequence of five direct causes: changes in land and sea use; direct exploitation of organisms; climate change; pollution; and invasion of alien species.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/revolutionary-change-needed-to-stop-unprecedented-global-extinction-crisis-116166">'Revolutionary change' needed to stop unprecedented global extinction crisis</a>
</strong>
</em>
</p>
<hr>
<p>It’s the last, invasive species, that threatens Australian animals and plants more than any other single factor.</p>
<h2>Australia’s number one threat</h2>
<p>Australia has an estimated <a href="https://www.environment.gov.au/system/files/pages/2ee3f4a1-f130-465b-9c7a-79373680a067/files/nlsaw-2nd-complete.pdf">600,000</a> species of flora and fauna. Of these, about <a href="https://www.csiro.au/en/Research/Environment/Biodiversity/Biodiversity-book">100</a> are known to have gone extinct in the last 200 years. Currently, more than 1,770 are listed as <a href="https://www.environment.gov.au/biodiversity/threatened/species">threatened or endangered</a>. </p>
<p>While the IPBES report ranks invasive alien species as the fifth most significant cause of global decline, in Australia it is a very different story. </p>
<p>Australia has the highest rate of vertebrate mammal extinction in the world, and invasive species are our number one threat. </p>
<p>Cats and foxes have driven 22 native mammals to extinction across central Australia and a new wave of decline – largely from cats – is taking place across northern Australia. <a href="http://www.publish.csiro.au/pc/PC18024">Research has estimated</a> 270 more threatened and endangered vertebrates are being affected by <a href="http://www.nespthreatenedspecies.edu.au/Kearney-et-al-2018_The-threats-to-Aus-species_postprint.pdf">invasive species</a>. </p>
<p>Introduced vertebrates have also driven several <a href="http://www.nespthreatenedspecies.edu.au/Kearney-et-al-2018_The-threats-to-Aus-species_postprint.pdf">bird species on Norfolk Island</a> extinct.</p>
<h2>The effects of invasive species are getting worse</h2>
<p>Although Australia’s stringent biosecurity measures have dramatically slowed the number of new invasive species arriving, those already here have continued to spread and their cumulative effect is growing. </p>
<p><a href="http://www.publish.csiro.au/pc/Fulltext/PC18024?subscribe=false%22">Recent research</a> highlights that 1,257 of Australia’s threatened and endangered species are directly affected by 207 invasive plants, 57 animals and three pathogens.</p>
<p>These affect our unique biodiversity, as well as the clean water and oxygen we breath – not to mention our cultural values.</p>
<p>When it comes to biodiversity, Australia is globally quite distinct. More than 70% of our species (69% of mammals, 46% of birds and 93% of reptiles) are <a href="https://www.csiro.au/en/Research/Collections/TenThingsAboutCollections">found nowhere else on earth</a>. A loss to Australia is therefore a loss to the world. </p>
<p>Some of these are ancient species like the Wollemi Pine, may have inhabited Australia for up to 200 million years, well <a href="https://theconversation.com/wollemi-pines-are-dinosaur-trees-98160">before the dinosaurs</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wollemi-pines-are-dinosaur-trees-98160">Wollemi pines are dinosaur trees</a>
</strong>
</em>
</p>
<hr>
<p>But invasive species are found in almost every part of Australia, from our rainforests, to our deserts, our farms, to our cities, our national parks and our rivers.</p>
<h2>The cost to Australia</h2>
<p>The cost of invasive species in Australia continue to grow with every new assessment. </p>
<p>The most recent estimates found the cost of controlling invasive species and economic losses to farmers in 2011-12 was A$13.6 billion. However this doesn’t include harm to biodiversity and the essential role native species play in our ecosystems, which – based on the conclusions of the IPBES report – is likely to cost at least as much, and probably far more.</p>
<p>Rabbits, goats and camels prevent native desert plant community regeneration; rabbits alone impacting over 100 threatened species. Rye grass on its own costs cereal farmers <a href="https://grdc.com.au/__data/assets/pdf_file/0027/.../grdc_weeds_review_r8.pdf.pdf">A$93M</a> a year. </p>
<p>Aquaculture diseases have affected oysters and cost the prawn industry <a href="https://www.abc.net.au/news/rural/2017-12-12/systematic...prawn-disease/9246796">$43M</a>. </p>
<h2>From island to savannah</h2>
<p>Globally, invasive species have a <a href="https://www.ncbi.nlm.nih.gov/pubmed/27001852">disproportionately higher effect</a> on offshore islands – and in Australia we have more than 8,000 of these. One of the most notable cases is the case of the <a href="https://theconversation.com/a-tiny-wasp-could-save-christmas-islands-spectacular-red-crabs-from-crazy-ants-69646">yellow crazy ants</a>, which killed 15,000,000 red land crabs on Christmas Island. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-tiny-wasp-could-save-christmas-islands-spectacular-red-crabs-from-crazy-ants-69646">A tiny wasp could save Christmas Island's spectacular red crabs from crazy ants</a>
</strong>
</em>
</p>
<hr>
<p>Nor are our deserts immune. Most native vertebrate extinctions caused by cats have occurred in our dry inland deserts and savannas, while exotic buffel and gamba grass are creating permanent transformation through changing fire regimes.</p>
<p>Australia’s forests, particularly rainforests, are also under siege on a number of fronts. The battle continues to contain Miconia weed in Australia – the same weed responsible for taking over <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2699.1996.tb00038.x">70% of Tahiti’s native forests</a>. Chytrid fungus, thought to be present in Australia since 1970, has caused the extinction of <a href="https://www.environment.gov.au/system/files/resources/279bf387-09e0-433f-8973-3e18158febb6/files/c-disease_1.pdf">at least four frog species</a> and dramatic decline of at least ten others in our sensitive rainforest ecosystems. </p>
<p>Myrtle rust is pushing already threatened native Australian Myrtaceae <a href="https://www.annualreviews.org/doi/full/10.1146/annurev-phyto-080516-035256">closer to extinction</a>, notably <em>Gossia gonoclada</em>, and <em>Rhodamnia angustifolia</em> and changing species composition of rainforest understories, and Richmond birdwing butterfly numbers are under threat from an <a href="https://link.springer.com/content/pdf/10.1007/978-94-007-7170-3.pdf">invasive flower</a> known as the Dutchman’s pipe.</p>
<p>Australia’s rivers and lakes are also under increasing domination from invasive species. Some 90% of fish biomass in the Murray Darling Basin are <a href="http://www.carp.gov.au/">European carp</a>, and <a href="https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/land-management/health-pests-weeds-diseases/pests/invasive-animals/restricted/tilapia">tilapia</a> are invading many far north Queensland river systems pushing out native species .</p>
<p>Invasive alien species are not only a serious threat to biodiversity and the economy, but also to human health. The <em>Aedes aegypti</em> mosquito found in <a href="https://theconversation.com/stowaway-mozzies-enter-australia-from-asian-holiday-spots-and-theyre-resistant-to-insecticides-113999">parts of Queensland</a> is capable of spreading infectious disease such as dengue, zika, chikungunya and yellow fever.</p>
<p>And it’s not just Queensland that is under threat from diseases spread by invasive mosquitoes, with many researchers and authorities planning for when, not if, the disease carrying <em>Aedes albopictus</em> establishes itself in <a href="https://theconversation.com/how-we-kept-disease-spreading-asian-tiger-mozzies-away-from-the-australian-mainland-72873">cooler and southern parts of Australia</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/stowaway-mozzies-enter-australia-from-asian-holiday-spots-and-theyre-resistant-to-insecticides-113999">Stowaway mozzies enter Australia from Asian holiday spots – and they're resistant to insecticides</a>
</strong>
</em>
</p>
<hr>
<h2>What solutions do we have?</h2>
<p>Despite this grim inventory, it’s not all bad news. Australia actually has a long history of effectively managing invasive species. </p>
<p>Targeting viruses as options for controlling rabbits, carp and tilapia; we have successfully suppressed rabbit populations by 70% in this way for <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1111/aehr.12000">50 years</a>.</p>
<p>Weeds too are successful targets for weed biological control, with over a 65% success rate controlling <a href="https://ebooks.publish.csiro.au/content/biological-control-weeds-australia">more than 25 targets</a>. </p>
<p>The IPBES report calls for “transformative action”. Here too Australia is at the forefront, looking into the potential of <a href="https://theconversation.com/weve-cracked-the-cane-toad-genome-and-that-could-help-put-the-brakes-on-its-invasion-103362">gene-technologies</a> to suppress pet hates such as cane toads.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/weve-cracked-the-cane-toad-genome-and-that-could-help-put-the-brakes-on-its-invasion-103362">We've cracked the cane toad genome, and that could help put the brakes on its invasion</a>
</strong>
</em>
</p>
<hr>
<p>Past and current invasive species programs have been supported by governments and industry. This has provided the type of investment we need for long-term solutions and effective policies.</p>
<p>Australia is better placed now, with effective biosecurity policies and strong biosecurity investment, than many countries. We will continue the battle against invasive species to stem biodiversity and ecosystem loss.</p><img src="https://counter.theconversation.com/content/116809/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andy Sheppard receives funding from CSIRO and Department of Environment & Energy. He is affiliated with IPBES and the CBD. </span></em></p><p class="fine-print"><em><span>Linda Broadhurst receives funding from RIRDC, GRDC, Land & Water Australia, ARC, Director of National Parks and the Department of the Environment and Energy.
Linda Broadhurst is President of the Australian Network for Plant Conservation.</span></em></p>Invasive species are the biggest single threat to Australian plants and animals.Andy Sheppard, Research Director CSIRO Health & Biosecurity, CSIROLinda Broadhurst, Director, Centre for Australian National Biodiversity Research, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1139972019-04-09T02:33:17Z2019-04-09T02:33:17ZHow indigenous expertise improves science: the curious case of shy lizards and deadly cane toads<figure><img src="https://images.theconversation.com/files/268196/original/file-20190408-2901-1tbo2ex.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Balanggarra Rangers are land management representatives of the Balanggarra people, the indigenous traditional owners of the East Kimberley. (L-R) Wes Alberts, Bob Smith (coordinator) James 'Birdy' Birch, Isiah Smith, Quentin Gore.</span> <span class="attribution"><span class="source">The Kimberley Land Council</span>, <span class="license">Author provided</span></span></figcaption></figure><p>It’s a common refrain – western ecologists should work closely with indigenous peoples, who have a unique knowledge of the ecosystems in their traditional lands. </p>
<p>But the rhetoric is strong on passion and weak on evidence. </p>
<p>Now, a <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/conl.12643">project</a> in the remote Kimberley area of northwestern Australia provides hard evidence that collaborating with Indigenous rangers can change the outcome of science from failure to success.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/weve-cracked-the-cane-toad-genome-and-that-could-help-put-the-brakes-on-its-invasion-103362">We've cracked the cane toad genome, and that could help put the brakes on its invasion</a>
</strong>
</em>
</p>
<hr>
<h2>Fighting a toxic invader</h2>
<p>This research had a simple but ambitious aim: to develop new ways to save at-risk predators such as lizards and quolls from the devastating impacts of invasive cane toads. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=629&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=629&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=629&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=791&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=791&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268192/original/file-20190408-2918-xhsmqt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=791&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cane toads are invasive and highly toxic to Australia’s apex predators.</span>
<span class="attribution"><span class="source">David Nelson</span></span>
</figcaption>
</figure>
<p>All across tropical Australia, the arrival of these gigantic alien toads has caused massive die-offs among meat-eating animals such as yellow-spotted monitors (large lizards in the varanid group) and quolls (meat-eating marsupials). Mistaking the new arrivals for edible frogs, animals that try to eat them are fatally poisoned by the toad’s powerful toxins. </p>
<p>Steep population declines in these predators ripple out through entire ecosystems. </p>
<p>But we can change that outcome. We expose predators to a small cane toad, big enough to make them ill but not to kill them. <a href="https://www.canetoadcoalition.com/the-strategy">The predators learn fast</a>, and ignore the larger (deadly) toads that arrive in their habitats a few weeks or months later. As a result, our trained predators survive, whereas their untrained siblings die.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-a-waterless-barrier-and-how-could-it-slow-cane-toads-114363">What is a waterless barrier and how could it slow cane toads?</a>
</strong>
</em>
</p>
<hr>
<h2>Conservation ‘on Country’</h2>
<p>But it’s not easy science. The site is remote and the climate is harsh. </p>
<p>We and our collaborators, the <a href="https://www.dbca.wa.gov.au/">Western Australian Department of Biodiversity, Conservation and Attractions</a>, decided at the outset that we needed to work closely with the Indigenous Traditional Owners of the east Kimberley – the <a href="https://www.nativetitle.org.au/find/pbc/2923">Balanggarra</a> people. </p>
<p>So as we cruised across the floodplain on quad bikes looking for goannas, each team consisted of a scientist (university-educated, and experienced in wildlife research) and a Balanggarra Indigenous ranger. </p>
<p>Although our study species is huge – a male yellow-spotted monitor can grow to more than 1.7 metres in length and weigh more than 6kg – the animals are well-camouflaged and difficult to find. </p>
<p>Over an 18-month study, we caught and radio-tracked more than 80 monitors, taught some of them not to eat toads, and then watched with trepidation as the cane toad invasion arrived. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-you-heard-right-more-cane-toads-really-can-help-us-fight-cane-toads-67241">Yes, you heard right: more cane toads really can help us fight cane toads</a>
</strong>
</em>
</p>
<hr>
<p>Excitingly, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4785923/">the training worked</a>. Half of our trained lizards were still alive by the end of the study, whereas all of the untrained lizards died soon after toads arrived.</p>
<p>That positive result has encouraged a <a href="https://www.canetoadcoalition.com/the-coalition-1">consortium</a> of scientists, government authorities, conservation groups, landowners and local businesses to implement aversion training on a massive scale (see <a href="https://www.canetoadcoalition.com">www.canetoadcoalition.com</a>), with support from the Australian Research Council. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268186/original/file-20190408-2901-118arch.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A yellow-spotted monitor fitted with a radio transmitter in our study. This medium-sized male was trained and lived for the entirety of the study in high densities of cane toads.</span>
<span class="attribution"><span class="source">Georgia Ward-Fear, University of Sydney</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/teaching-reptiles-to-avoid-cane-toads-earns-top-honour-in-pms-science-prizes-67306">Teaching reptiles to avoid cane toads earns top honour in PM's science prizes</a>
</strong>
</em>
</p>
<hr>
<h2>Cross-cultural collaboration key to success</h2>
<p>But there’s a twist to the tale, a vindication of our decision to make the project truly collaborative. </p>
<p>When we looked in detail at our data, we realised that the monitor lizards found by Indigenous rangers were different to those found by western scientists. The rangers found shyer lizards, often further away from us when sighted, motionless, and in heavy cover where they were very difficult to see. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268130/original/file-20190408-2898-jhtsb6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Gregory Johnson, Balanggarra elder and ranger.</span>
<span class="attribution"><span class="source">Georgia Ward-Fear</span></span>
</figcaption>
</figure>
<p>We don’t know how much the extraordinary ability of the rangers to spot those well-concealed lizards was due to genetics or experience – but there’s no doubt they were superb at finding lizards that the scientists simply didn’t notice. </p>
<p>And reflecting the distinctive “personalities” of those ranger-located lizards, they were the ones that benefited the most from aversion training. Taking a cautious approach to life, a nasty illness after eating a small toad was enough to make them swear off toads thereafter. </p>
<p>In contrast, most of the lizards found by scientists were bold creatures. They learned quickly, but when a potential meal hopped across the floodplain a few months later, the goanna seized it before recalling its previous experience. And even holding a toad briefly in the mouth can be fatal.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=609&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=609&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=609&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=766&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=766&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268121/original/file-20190408-2921-zyshzo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=766&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Comparisons of conditions under which lizards were initially sighted in the field by scientists and Indigenous rangers (a) proximity to lizards in metres (b) density of ground-cover vegetation (>30cm high) surrounding the lizard (c) intensity of light directly on lizard (light or shade) (d) whether the lizard was stationary or moving (i.e. walking or running). Sighting was considered more difficult if lizards were further away, in more dense vegetation, in shade, and stationary.</span>
<span class="attribution"><span class="source">Georgia Ward-Fear, University of Sydney</span></span>
</figcaption>
</figure>
<p>As a result of the intersection between indigenous abilities and lizard personalities, the overall success of our project increased as a result of our multicultural team. </p>
<p>If we had just used the conventional model – university researchers doing all of the work, indigenous people asked for permission but playing only a minor role – our project could have failed, and the major conservation initiative currently underway may have died an early death. </p>
<p>So our study, now published in <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/conl.12643">Conservation Letters</a>, provides an unusual insight – backed up by evidence. </p>
<p>Moving beyond lip service, and genuinely involving Indigenous Traditional Owners in conservation research, can make all the difference in the world. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268131/original/file-20190408-2921-xyzez5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Georgia Ward-Fear (holding a yellow-spotted monitor) with Balanggarra Rangers Herbert and Wesley Alberts.</span>
<span class="attribution"><span class="source">David Pearson, WA Department of Biodiversity, Conservation and Attractions</span></span>
</figcaption>
</figure>
<hr>
<p><em>This research was published in collaboration with James “Birdy” Birch and his team of Balanggarra rangers in the eastern Kimberley.</em></p><img src="https://counter.theconversation.com/content/113997/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Georgia Ward-Fear receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Rick Shine receives funding from the Australian Research Council.</span></em></p>There are exciting synergies between western science and indigenous knowledge. Surprisingly, the success of our Australian predator conservation research was due entirely to its multicultural nature.Georgia Ward-Fear, Post doctoral fellow and Conservation Ecologist , University of SydneyRick Shine, Professor in Evolutionary Biology, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1095742019-01-10T18:24:34Z2019-01-10T18:24:34ZThe economics of ‘cash for cane toads’ – a textbook example of perverse incentives<figure><img src="https://images.theconversation.com/files/253175/original/file-20190110-32154-1exnbqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It is estimated there are now more than 200 million cane toads across Queensland and northern New South Wales. </span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Economics teachers can all thank Pauline Hanson for providing an excellent example to add to their classes. </p>
<p>Indeed, it’s rare that Economics 101 lessons are as readily on display as in the Queensland senator’s “cash for cane toads” proposal. </p>
<p>Both textbook wisdom and historical failures tell us the plan won’t work.</p>
<p>Hanson’s proposal involves paying welfare recipients 10 cents for each toad they collect (alive) and hand over to their local council. The council would then kill the toads humanely in large freezers.</p>
<p>The senator is right to be concerned about the cane toad problem. Introduced in the 1930s as a biological fix to control native beetles eating sugar cane crops, the animals have prospered with <a href="https://www.environment.nsw.gov.au/topics/animals-and-plants/pest-animals-and-weeds/pest-animals/cane-toads">devastating impact</a> on native flora and fauna. It’s estimated there are now more than <a href="https://www.nationalgeographic.com/animals/amphibians/c/cane-toad/">200 million</a> across Queensland and northern New South Wales. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/weve-cracked-the-cane-toad-genome-and-that-could-help-put-the-brakes-on-its-invasion-103362">We've cracked the cane toad genome, and that could help put the brakes on its invasion</a>
</strong>
</em>
</p>
<hr>
<p>They carry toxins at all stages of their life cycle, including as eggs. Ingesting the toxin is fatal to many Australian species. Their voracious appetites both deplete insect populations such as honey bees and threaten the food sources of other native animals.</p>
<p>The reason Hanson’s idea is fundamentally flawed, both in theory and in practice, has to do with incentives.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/253176/original/file-20190110-32133-lhf0hn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A native of Latin America, the cane toad has adapted well to Australia due to the lack of natural predators. Toads have spread from Queensland as far west as Broome, Western Australia.</span>
<span class="attribution"><span class="source">www.shutterstock.com</span></span>
</figcaption>
</figure>
<h2>History repeating</h2>
<p>Incentives are central to economics. They are ingrained in the laws of demand and supply, and the setting of interest rates and taxes. </p>
<p>Humans react to incentives. The key is setting them just right by accounting for all of the costs involved. </p>
<p>This is the most obvious and least interesting problem with the scheme. In NSW and Queensland, you can earn 10 cents by returning an empty drink container to your local supermarket. That’s a task exponentially easier than catching a cane toad and delivering it alive to your local council chambers. </p>
<p>If it were just a case of the incentives being too low, the solution would be simple: raise the price. </p>
<p>However, this would run into a surprising phenomenon called the <a href="https://en.wikipedia.org/wiki/Cobra_effect">Cobra effect</a>. Also known as “perverse incentives”, it describes a situation in which a seemingly well-intentioned proposal actually makes things much worse. </p>
<p>The Cobra effect is named after a curious incident from British Colonial India. Faced with a cobra outbreak, the local government of Delhi enacted a cash-for-cobras scheme, with initial success. But as cobras became harder to find, the locals responded to the incentives in a completely logical way: they started breeding the snakes to claim their bounties. When the scheme was scrapped, breeders released their now-worthless snakes, resulting in the city having more cobras than before the scheme. </p>
<p>A <a href="https://www.atlasobscura.com/articles/hanoi-rat-massacre-1902">similar case</a> comes from French-run Vietnam. </p>
<p>When the colonial government built a sewerage system under Hanoi early in the 20th century, it inadvertently helped create a rat plague. Its solution was a cash-for-rats scheme - though to save the government having to dispose of hundreds of thousands of rat carcasses, it only required collectors turning in a rat’s tail to claim their bounty. </p>
<h2>Crowd displeasers</h2>
<p>The consequences this time were not only the creation of pop-up rat-breeding farms, but also hordes of tail-less rats roaming the city streets.</p>
<p>Of course, at its current pittance of 10 cents a toad, Hanson’s proposal is unlikely to lead to lucrative cane-toad farming. </p>
<p>It’s a reasonable claim that the incentives would simply be too low to be effective, leading to no change in the status quo (besides large freezers sitting empty at local council buildings). </p>
<p>Yet even as a toothless policy, a cash-for-cane-toads scheme could produce other unintended consequences.</p>
<p>When people already do something out of their own goodness, like volunteering, putting a price on the activity by offering chump change can actually put them off. Behavioural economists call this “<a href="https://www.aeaweb.org/articles?id=10.1257/jel.50.2.368">crowding out of intrinsic motivation</a>”. It explains why blood donation rates are no different between countries that pay donors (such as the United States) and those that rely on volunteers (such as Australia). </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/for-love-not-money-kidney-exchange-encourages-social-contract-4054">For love, not money: kidney exchange encourages social contract </a>
</strong>
</em>
</p>
<hr>
<p>One of the <a href="https://www.journals.uchicago.edu/doi/10.1086/468061">best-known examples</a> in economics involved a day-care in Israel that introduced small fines for parents who were late picking up their children. The result was a doubling of lateness. Before the fine, parents would try to come on time because it was the right thing to do. After the fine, however, that moral value had a price: about three dollars. </p>
<p>Notably, parents continued to come late after the fines were removed. Parents who pay pocket money for chores need only imagine how their own kids would respond if they moved to a “volunteer system”.</p>
<p>Thus economics gives us a third reason to doubt Senator Hanson’s proposal will work: the risk that altruistic citizens who have culled cane toads for free will be discouraged by a price being put on the activity. </p>
<p>Instead of considering the “priceless” value of native ecosystems when spotting an offending creature, people may start weighing up their efforts against 10 cents. This cost-benefit thinking could continue even after the compensation scheme ends. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/253178/original/file-20190110-32151-1fq3hfu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The cane toad is the world’s largest toad. An adult’s body is typically 10-15 cm in length, but some grow at large as 24 cm.</span>
<span class="attribution"><span class="source">www.shutterstock.com</span></span>
</figcaption>
</figure>
<p>That’s the crux of why this payment scheme wouldn’t work. Setting a high price perverts the incentives, while setting a low price crowds out intrinsic motivations. In either case, taxpayer money is wasted and the toad problem is potentially made worse. </p>
<p>The best approach is to leave prices out of it and trust our experts, who are continuing to come up with <a href="https://theconversation.com/come-hither-how-imitating-mating-males-could-cut-cane-toad-numbers-93484">remarkably innovative ideas</a> to solve the cane toad problem.</p>
<p>Senator Hanson’s proposal was no doubt made with the best of intentions. Unfortunately, in reality the only real beneficiaries would be economics teachers.</p><img src="https://counter.theconversation.com/content/109574/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Smerdon does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Pauline Hanson’s idea to reduce cane toad numbers is fundamentally flawed, both in economic theory and in practice.David Smerdon, Assistant Professor, School of Economics, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1033622018-09-19T20:13:25Z2018-09-19T20:13:25ZWe’ve cracked the cane toad genome, and that could help put the brakes on its invasion<figure><img src="https://images.theconversation.com/files/237014/original/file-20180919-143281-y2z5wl.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cane toads are on the march, but new genetic research could slow them down.</span> <span class="attribution"><span class="source">Michael Linnenbach</span></span></figcaption></figure><p>We and our international colleagues have deciphered the genetic code of the cane toad. The complete sequence, <a href="https://academic.oup.com/gigascience/advance-article/doi/10.1093/gigascience/giy095/5067871">published today in the journal GigaScience</a>, will help us understand how the toad can quickly evolve to adapt to new environments, how its infamous toxin works, and hopefully give us new options for halting this invader’s march across Australia.</p>
<p>Since its introduction into Queensland in 1935, the cane toad has spread widely and now occupies <a href="http://rspb.royalsocietypublishing.org/content/274/1616/1413">more than 1.2 million square kilometres of Australia</a>. It is fatally poisonous to predators such as the northern quoll, freshwater crocodiles, and several species of native lizards and snakes.</p>
<p>Previous attempts to sequence the cane toad, by WA researchers more than 10 years ago, were <a href="http://www.news.uwa.edu.au/oct-2007/new-research-funding-awarded-help-find-cane-toad-achilles-heel">not successful</a>, largely because the existing technology could not assemble the genetic pieces to create a genome. But thanks to new methods, we have succeeded in piecing together the entire genetic sequence.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-you-heard-right-more-cane-toads-really-can-help-us-fight-cane-toads-67241">Yes, you heard right: more cane toads really can help us fight cane toads</a>
</strong>
</em>
</p>
<hr>
<p>Our team, which also featured researchers from Portugal and Brazil, worked at the <a href="https://www.ramaciotti.unsw.edu.au/">Ramaciotti Centre for Genomics</a> at UNSW. This centre played a key role in decoding the genomes of other iconic Australian species, including the koala.</p>
<p>Sequencing, assembling and annotating a genome (working out which genes go where) is a complicated process. The cane toad genome is similar in size to that of humans, at roughly 3 billion DNA “letters”. By using cutting-edge technology, our team sequenced more than 360 billion letters of cane toad DNA code, and then assembled these overlapping pieces to produce one of the best-quality amphibian genomes to date.</p>
<p>We deduced more than 90% of the cane toad’s genes using technology that can sequence very long pieces of DNA. This made the task of putting together the genome jigsaw much easier.</p>
<h2>Toxic toads</h2>
<p>The cane toad has iconic status in Australia, with many Aussies loving to hate the poisonous invasive amphibian. This is a little unfair. It’s not the cane toad’s fault – it was humans who chose to bring it to Australia. </p>
<p>Our obsession with sugar in the 1800s led to the toad’s introduction to many countries around the world. Wherever sugar cane was planted, the cane toad followed, taken from plantation to plantation by landowners as the warty interlopers travelled from South America to the Caribbean and then on to Hawaii and Australia. </p>
<p>But unlike most other places to which the cane toad was introduced, Australia lacks any native toads of its own. The cane toad’s powerful poisons are deadly to native species that have never before encountered this amphibian’s arsenal.</p>
<p>The cane toad has therefore been subject to detailed evolutionary and ecological research in Australia, revealing not only its impact but also its amazing capacity for rapid evolution. Within 83 years of its introduction, cane toads in Australia have evolved a wide range of modifications that affect their body shape, physiology and behaviour. </p>
<p>For example, cane toads at the invasion front are longer-legged and bolder than those in long-colonised areas and invest less into their immune defences (for a summary, see <a href="https://www.ucpress.edu/book/9780520295100/cane-toad-wars">Cane Toad Wars</a> by Rick Shine). </p>
<p>The new genome will give us insights into how evolution transformed a sedentary amphibian into a formidable invasion machine. And it could give us new weapons to help stop, or at least slow, this invasion.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/aJF_C6c_f8U?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Cracking the cane toad genome.</span></figcaption>
</figure>
<h2>Viral control</h2>
<p>Current measures such as physical removal have not been successful in preventing cane toads from spreading, so fresh approaches are needed. One option may be to use a virus to help control the toad population. </p>
<p>Viruses such as myxomatosis have been <a href="https://theconversation.com/tandem-virus-cocktail-kills-pest-rabbits-more-effectively-97930">successfully used to control rabbits</a>. But the cane toad viruses <a href="https://doi.org/10.1111/j.1469-1795.2009.00319.x">studied so far</a> are also infectious to native frogs. The new genome could potentially help scientists hunt for viruses that attack only toads. </p>
<p>In a <a href="https://jvi.asm.org/content/early/2018/06/07/JVI.00768-18">study published this month</a>, we and other colleagues describe how we sampled genetic sequences from cane toads from different Australian locations, and found three viruses that are genetically similar to viruses that infect frogs, reptiles and fish. These viruses could potentially be used as biocontrol agents, although only after comprehensive testing to check that they pose no danger to any other native species.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/come-hither-how-imitating-mating-males-could-cut-cane-toad-numbers-93484">Come hither... how imitating mating males could cut cane toad numbers</a>
</strong>
</em>
</p>
<hr>
<p>The full cane toad genome will help to accelerate this kind of research, as well as research on the toads’ evolution and its interactions with the wider ecosystem. The published sequence is freely available for anyone to use in their studies. It is one of very few amphibian genomes sequenced so far, so this is also great news for amphibian biologists in general. </p>
<p>As the cane toads continue their march across the Australian landscape, this milestone piece of research should help us put a few more roadblocks in their path.</p><img src="https://counter.theconversation.com/content/103362/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Shine receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Alice Russo and Peter White do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New genetic knowledge about cane toads could give us the knowledge we need to throw some more roadblocks in front of this persistent invader as it marches across Australia.Peter White, Professor in Microbiology and Molecular Biology, UNSW SydneyAlice Russo, PhD candidate, UNSW SydneyRick Shine, Professor in Evolutionary Biology, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/977282018-06-04T15:08:25Z2018-06-04T15:08:25ZAn invasion of toxic toads threatens Madagascar’s vulnerable wildlife<figure><img src="https://images.theconversation.com/files/221549/original/file-20180604-175451-zmgfog.jpg?ixlib=rb-1.1.0&rect=3%2C13%2C1274%2C754&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Ben Marshall</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Madagascar is in the midst of a toxic invasion. Since around 2010, an army of invasive Asian toads (<em>Duttaphrynus melanostictus</em>) has gained a foothold in and around the eastern port of Toamasina after they were accidentally introduced from South-East Asia. This has dismayed conservationists who worry about the island’s already <a href="http://journals.sagepub.com/doi/abs/10.1177/194008291500800210">beleaguered endemic fauna</a>. </p>
<p>Now, our worst fears have been confirmed by recent findings by a research team led by Bangor University masters student Ben Marshall and including myself. In our <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(18)30452-4">new study</a> published in Current Biology, we show that most of Madagascar’s unique native wildlife can indeed be poisoned by the introduced toad.</p>
<p>Invasive species are one of the major drivers of extinction worldwide. Most impact native species by eating them (cats, rats), competing with them (grey squirrels in the UK) or altering local vegetation (rabbits, goats). Invasive toads, on the other hand, primarily affect native predators through their skin toxins, poisoning any animal that takes a toad into its mouth. “True toads”, of the family Bufonidae, synthesise <a href="https://www.ncbi.nlm.nih.gov/pubmed/6245447">potent toxins</a> in large prominent parotoid glands on their backs. These “bufotoxins” impede the regulation of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3079441/">sodium and potassium levels in cells</a>, leading to rapid heart failure and death.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=479&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=479&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=479&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=602&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=602&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221565/original/file-20180604-175400-19bwfgg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=602&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Madagascar’s tree snakes are found nowhere else on Earth.</span>
<span class="attribution"><span class="source">M Vences</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Where toads occur naturally, some predators avoid them, but others have <a href="https://doi.org/10.1073/pnas.1511706112">evolved resistance</a> to their toxins, allowing them to routinely eat toads. Recent investigations have revealed the mechanism of resistance: two specific amino acid substitutions in the target molecule of bufotoxin, the ATPase sodium-potassium pump, are all that is required to change a dangerously poisonous toad into a <a href="https://doi.org/10.1073/pnas.1511706112">potential meal</a>. Remarkably, the same solution has evolved in a diverse array of species, from rats to lizards to the toads themselves, and this appears to be the only way for any vertebrate to resist the toads’ toxins.</p>
<p>The problem for Madagascar’s animals is they developed on an island with plenty of frogs but <a href="http://www.wildmadagascar.org/wildlife/frogs.html">no toads</a>. Native species therefore had no reason to evolve any resistance to toad toxins nor any sense that they should avoid toads.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221572/original/file-20180604-175445-1hwxu16.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Toxic toad making friends in a Madagascar village.</span>
<span class="attribution"><span class="source">Franco Andreone</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>And when toads do invade these previously toad-free areas, it may result in mass mortality among some naive predators. For instance the infamous <a href="https://www.researchgate.net/publication/47334877_The_Ecological_Impact_of_Invasive_Cane_Toads_Bufo_Marinus_in_Australia">cane toad invasion of Australia</a> caused larger apex predators, such as monitor lizards, some snakes and the marsupial quolls to become locally rare or extinct. This in turn affected numerous other species in the food web, though some, such as some smaller lizards and snakes, actually flourished due to the removal of the larger predators.</p>
<h2>Searching for resistance</h2>
<p>So will Madagascar’s predators suffer just like Australia’s? As we now know that there is a single molecule responsible for toad resistance in vertebrates, this gives biologists an invaluable tool: simply examining the relevant gene will reveal whether an animal can eat a toad with impunity or is liable to be poisoned.</p>
<p>In our study, we used this approach on a range of Malagasy predators. The results confirmed our worst fears: out of 29 reptiles, eight mammals, 12 frogs and 28 birds tested, all except one rodent (the white-tailed antsangy) lack resistance to toad toxins.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=421&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=421&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=421&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=529&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=529&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221568/original/file-20180604-175400-1bhxtuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=529&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Toad-proof: the white-tailed antsangy.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:BrachytarsomysAlbicaudataWolfSmit.jpg">Joseph Wolf & Joseph Smit</a></span>
</figcaption>
</figure>
<p>This presents an immediate conservation concern in an already troubled <a href="https://doi.org/10.1038/35002501">biodiversity hotspot</a>, and has serious implications for the many species that exist only on Madagascar. For instance, all Malagasy snakes tested are vulnerable to toad toxins, and <a href="http://www.amphibians.org/wp-content/uploads/2016/03/Asian-Toad-Feasibility-Report-26th-Jan-2016.pdf">anecdotal reports</a> have already documented snakes dying from eating toads. </p>
<p>It gets worse: in the past, a loss of snakes has led to booms in rodent populations and fears over public health. Such fears are warranted once again, given that non-native rats are <a href="https://pubs.acs.org/doi/abs/10.1021/bi00422a016">resistant to bufotoxins</a>.</p>
<p>However, rodents appear to be unique in this respect. Among the toad-sensitive mammals are Madagascar’s most charismatic and widely recognised residents. Three representatives from three lemur families are vulnerable. Fortunately lemurs eat plants and sometimes insects, and only <a href="http://repository.kulib.kyoto-u.ac.jp/dspace/handle/2433/143673">rarely prey on small vertebrates</a>, which will likely limit the toad’s impact on them. The same cannot be said for the carnivores of Madagascar: the habits of the enigmatic fossa and others make them <a href="http://eprints.kingston.ac.uk/35733/1/Brown-K-35733-AAM.pdf">extremely likely to encounter and consume</a> the toxic invader.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221570/original/file-20180604-175407-z31ud8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The cat-like fossa will eat anything from lemurs to lizards.</span>
<span class="attribution"><span class="source">Dudarev Mikhail/Shutterstock</span></span>
</figcaption>
</figure>
<p>As cane toads in Australia highlighted, it’s tough to predict <a href="https://www.ucpress.edu/book/9780520295100/cane-toad-wars">exactly which species</a> will be most affected by an invader. The sharing of habits and habitats will likely be the biggest factor influencing how much the toad will impact a species, but subtle differences in their interactions can make big differences to the outcome. For instance, <a href="https://www.researchgate.net/publication/23314953_Impact_of_the_invasive_cane_toad_Bufo_marinus_on_an_Australian_frog_Opisthodon_ornatus_depends_on_reproductive_timing">small variations in breeding times</a> made large differences in the relative success of native and invasive tadpoles in Australia.</p>
<p>Possible hope comes in the form of animals’ unrelenting ability to adapt. Australia offers <a href="https://www.researchgate.net/publication/263023395_A_small_dasyurid_predator_Sminthopsis_virginiae_rapidly_learns_to_avoid_a_toxic_invader">many examples</a> of native species evolving or learning quickly to <a href="https://academic.oup.com/beheco/article/21/5/966/197746">avoid toads</a>, or to only <a href="https://www.academia.edu/15751130/Toad_s_tongue_for_breakfast_exploitation_of_a_novel_prey_type_the_invasive_cane_toad_by_scavenging_raptors_in_tropical_Australia">eat the least toxic parts</a> of toads. Whether vulnerable Malagasy species, restricted to much more fragmented habitat patches serving as their final refuges, can display similar resilience remains to be seen.</p>
<p>The invasion of Madagascar by these toads has attracted <a href="https://www.researchgate.net/publication/262696887_Ecology_Stop_Madagascar%27s_toad_invasion_now">considerable attention</a>, but initial efforts to eliminate them have <a href="https://www.conservationevidence.com/individual-study/6851">faltered</a>. We hope that the confirmation that these toads pose a real threat to native species will reinvigorate efforts to protect native species from the toad’s further expansion.</p><img src="https://counter.theconversation.com/content/97728/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wolfgang Wüster does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New study confirms fears that the island’s native wildlife can be poisoned by introduced Asian toads.Wolfgang Wüster, Senior Lecturer in Zoology, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/934842018-03-21T04:47:19Z2018-03-21T04:47:19ZCome hither… how imitating mating males could cut cane toad numbers<p>Cane toads are a real Aussie success story – for themselves, at least. But research has produced a new kind of trap that may help stop their insidious march south.</p>
<p>The new traps imitate cane toads’ mating calls and also use UV lights to attract insects, enticing both male and female toads to the trap. </p>
<p>There are too many toads in Australia to eradicate by simply removing individuals – some estimates put the number as high as 1.5 billion – but we hope that eliminating reproducing females could slow population growth.</p>
<h2>Toad-ally awful</h2>
<p>In 1935, 102 toads were shipped from <a href="https://theconversation.com/everyone-agreed-cane-toads-would-be-a-winner-for-australia-19881">Hawaii to Queensland</a> to help control the cane beetle that were attacking sugar cane crops. They weren’t particularly effective at that job, but they were certainly successful at spreading. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/everyone-agreed-cane-toads-would-be-a-winner-for-australia-19881">Everyone agreed: cane toads would be a winner for Australia</a>
</strong>
</em>
</p>
<hr>
<p>Although no one knows for sure exactly how many cane toads are in Australia now, we do know that they have spread from the tropical Top End, through Darwin to the Kimberley in Western Australia, west to Longreach in western Queensland, and even as far south as Sydney. </p>
<p>Cane toads <a href="https://theconversation.com/great-invaders-poison-could-also-be-its-downfall-7609">reproduce rapidly</a>, and are <a href="https://phys.org/news/2018-01-invading-toads-adjusting-rapidly-environmental.html">very adaptable</a> and extremely mobile, covering up to a kilometre a night in the <a href="http://www.publish.csiro.au/WR/WR08021">right conditions</a>. They can also hitch rides on trucks, cars and even planes (hitching a ride is probably how a cane toad ended up in Mount Kosciuszko National Park <a href="http://www.abc.net.au/news/2017-03-22/cane-toad-found-at-mount-kosciuszko-national-park/8374726">last year</a>).</p>
<p>As they spread they wreak havoc on the native environment. Toads are highly toxic, making native predators like quolls, goannas and snakes sicken or die.</p>
<p>And while the toads only eat about as many insects as native frogs of the same size, their sheer population numbers mean they are likely to reduce the food availabile for other ground-dwelling insect-eaters, such as geckos, frogs, and some small mammals. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-you-heard-right-more-cane-toads-really-can-help-us-fight-cane-toads-67241">Yes, you heard right: more cane toads really can help us fight cane toads</a>
</strong>
</em>
</p>
<hr>
<h2>Using cane toad calls to trap adult toads</h2>
<p>In our laboratory we study frog calls. Male cane toads, like most frogs and toads, make a species-specific call to attract mates. About 15 years ago, we thought it might be possible to attract toads into traps using that call – which is, after all, for <a href="http://www.publish.csiro.au/WR/WR06173">attracting females</a>. </p>
<p>To our surprise, we found that both males and females were attracted to this call, and that although males are attracted to anything that sounds even a bit like a toad, <a href="https://www.sciencedirect.com/science/article/pii/S0003347215003127">females prefer certain call types</a>. </p>
<p>We also found that toads are attracted to insects that are attracted to lights, despite the paradoxical fact that toads <a href="https://www-tandfonline-com.elibrary.jcu.edu.au/doi/abs/10.1080/09670874.2015.1058991">don’t like white lights very much</a>. </p>
<p>We solved this problem by using UV lights to attract insects without bothering the toads. We then built traps that coupled UV lights to draw in insect food for the toads with the right call type, which were <a href="https://link.springer.com/article/10.1007/s10340-014-0555-9">more successful</a> than traps without both. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211289/original/file-20180321-80654-g2el0i.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Our traps use audio recordings of male mating calls and insect-attracting UV lights to make the cage appealing to both male and female cane toads.</span>
<span class="attribution"><span class="source">Eric Nordberg</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>James Cook University has been working with our industry partner, Animal Control Technologies Australia, to develop a functional trap people can use to get rid of adult toads. Our trap captures adult (breeding age) males and females before they reproduce, targeting future generations as well as the individuals themselves.</p>
<h2>Solving the ultimate problem</h2>
<p>Although we have known cane toads threaten our native wildlife for some time, there are still no strategies available to control their numbers, apart from removing them by hand. </p>
<p>Our research has shown that trapping is less <a href="https://www-tandfonline-com.elibrary.jcu.edu.au/doi/full/10.1080/09670874.2017.1363443">labour intensive than hand capture, and can be conducted for long periods</a>. Trapping may be useful as part of general strategies to reduce toad numbers in sensitive areas, for example on islands. <a href="https://theconversation.com/great-invaders-poison-could-also-be-its-downfall-7609">Traps for tadpoles</a> are presently being trialled around Brisbane. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/great-invaders-poison-could-also-be-its-downfall-7609">Great invader's poison could also be its downfall</a>
</strong>
</em>
</p>
<hr>
<p>Trapping may also be a good way to collect individuals to apply any control methods invented in the future. This may be a genetically engineered disease, or ongoing efforts to genetically alter toads to make them <a href="https://www.journals.uchicago.edu/doi/abs/10.1086/692167">non-toxic</a>. </p>
<p>Other mitigation strategies currently being tested include <a href="https://theconversation.com/teaching-reptiles-to-avoid-cane-toads-earns-top-honour-in-pms-science-prizes-67306">training native species not to eat toads</a>, either directly or using distasteful baits, and establishing <a href="https://theconversation.com/building-fences-could-stop-cane-toads-in-their-tracks-37092">natural dry barriers</a> that slow toad spread.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/building-fences-could-stop-cane-toads-in-their-tracks-37092">Building fences could stop cane toads in their tracks</a>
</strong>
</em>
</p>
<hr>
<p>We hope that traps for adults will become part of an arsenal of methods available to combat these pests, both at and behind the invasion front.</p><img src="https://counter.theconversation.com/content/93484/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lin Schwarzkopf works in partnership with Animal Control Technologies Australia, a for-profit company that partners with James Cook University via a Linkage grant. This cane toad research was also funded by a Caring for Country grant from the federal government.</span></em></p>New cane toad traps that carefully imitate mating males successfully target breeding females. Males, meanwhile, will turn up for anything that sounds remotely like a toad.Lin Schwarzkopf, Professor in Zoology, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/672412016-10-20T19:17:39Z2016-10-20T19:17:39ZYes, you heard right: more cane toads really can help us fight cane toads<p>Eighty years ago, an agricultural scientist named <a href="http://adb.anu.edu.au/biography/mungomery-reginald-william-reg-11197">Reginald Mungomery</a> brought cane toads to Australia, bred them, and released their offspring in sugar cane plantations near Cairns. Little did he know that he was setting in train one of the greatest ecological disasters to befall Australian wildlife. His decision has been universally condemned since. </p>
<p>But now, almost a century later, I am proposing that we can fix Mungomery’s historic blunder by doing almost exactly what he did. Ironically, we can buffer the devastating impact of the cane toad invasion by releasing juvenile toads at the invasion front.</p>
<p>This idea might sound ludicrous. The idea of releasing even more cane toads sounds like the height of academic folly. But it works, and my colleagues and I have even managed to convince initially sceptical management authorities and private landowners to adopt the method.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8MWia6qD_vM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Teaching reptiles to avoid cane toads. Animation courtesy of the University of Sydney.</span></figcaption>
</figure>
<p>Our key discovery was that populations of most species of native predators aren’t affected by the toad invasion. A few individuals are fatally poisoned when they eat a toxic toad, but most predators aren’t killed by such a meal. If the toad it eats is fairly small (and thus not too poisonous), the predator becomes ill, and learns not to eat toads in future. After that learning experience, the predator can coexist indefinitely with cane toads – it doesn’t try to eat them, so it’s not at risk.</p>
<p>So why doesn’t this same kind of learning save the larger predators – such as quolls, goannas, bluetongue skinks and snakes – that die in droves as soon as cane toads arrive in an area? Our <a href="http://onlinelibrary.wiley.com/store/10.1111/1365-2435.12044/asset/fec12044.pdf;jsessionid=857B055045C88E7475F6E02CB94FBA79.f03t04?v=1&t=iuhz3nnb&s=c4858c360aef4b0e3a5c4203218a237e76f50693">surveys</a> show up to 95% mortality in these species. </p>
<p>The reason is that these large predators attack large toads, and these toads contain more than enough poison to kill even a massive goanna within minutes.</p>
<p>Sadly, the apex predators never get an opportunity to encounter the smaller toads that could have offered them a lifeline by teaching them to steer well clear.</p>
<h2>On the frontline</h2>
<p>The invasion vanguard is dominated by <a href="https://theconversation.com/cane-and-able-how-superfit-toads-got-the-hop-on-evolution-512">large adult toads</a>, of a size that kills rather than educates any predator who eats it. Smaller toads (and reproductive females, heavy with eggs) aren’t at the frontline because they can’t keep up with the fastest invaders. As a result, cane toads don’t usually breed until a year or two after the first wave arrives – and by the time the area contains small as well as large toads, the predators have already been killed.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1065&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1065&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1065&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1338&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1338&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142475/original/image-20161020-8872-1oz24h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1338&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Size matters when it comes to cane toads.</span>
</figcaption>
</figure>
<p>So native predators face a stark equation. If the first cane toad you meet is a large one, you die. If the first cane toad you meet is a small one, you learn not to eat toads, and you survive.</p>
<p>This suggests a straightforward way to buffer the ecological impact of the cane toad invasion: ensure that the predator’s first meeting is with a small toad rather than a large one. There’s a very easy way to do this: we can release small toads at the invasion front, or induce aversion by other methods (such as feeding native animals <a href="https://www.theguardian.com/science/2016/oct/19/cane-toad-sausages-help-biologist-win-top-science-prize">toad-flavoured sausages</a>).</p>
<h2>Getting results</h2>
<p>We have <a href="http://onlinelibrary.wiley.com/doi/10.1111/acv.12004/abstract">trialled this method</a>, and <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2010.01802.x/abstract">it works</a>. Three of the most vulnerable species – Northern Quolls, Bluetongue Skinks, and Yellow-spotted Goannas – all survive toad invasion if they are trained beforehand, but die if they are not. </p>
<p>For example, my research colleague Georgia Ward-Fear captured goannas on a Kimberley floodplain, radio-tracked them, and dangled small cane toads in front of some of the lizards. Many of them seized on the toad, became nauseous, and avoided toads afterwards. Of the goannas that Georgia trained in this way, half were still alive at the conclusion of her <a href="http://rsbl.royalsocietypublishing.org/content/roybiolett/12/1/20150863.full.pdf">study</a> 18 months later – whereas all of the untrained lizards died long before then.</p>
<p>But isn’t this just a stopgap solution, delaying the wave of predator deaths for just a single generation? Won’t the offspring of those trained predators need to be trained as well, and so on forever? No, they won’t. </p>
<p>Within a year or two of the toads’ arrival in an area, they begin to breed – and so the offspring of our trained predators grow up in a world with small as well as large cane toads. The young predators will encounter small toads, eat them, and learn to give them a wide berth. All we need is a single generation of education to provide a long-lasting benefit.</p>
<p>We are now working with Western Australia’s Department of Parks and Wildlife to fine-tune our methods, and then implement them on a landscape scale. We can’t stop the toad invasion from proceeding through the Kimberley, but we can substantially blunt the invaders’ impact. Ironically, the way we are doing it is almost exactly the same as the act that caused the problem in the first place, when Reginald Mungomery released those first young cane toads in cane fields on the other side of the continent.</p>
<hr>
<p><em>Rick Shine is the <a href="https://theconversation.com/teaching-reptiles-to-avoid-cane-toads-earns-top-honour-in-pms-science-prizes-67306">recipient of the 2016 Prime Minister’s Prize for Science</a> for his work on the cane toad problem.</em></p><img src="https://counter.theconversation.com/content/67241/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Shine receives funding from the Australian Research Council and the University of Sydney.</span></em></p>It sounds weird, but releasing small cane toads ahead of the main invasion front can help predators learn to avoid the biggest, most toxic ones. Here’s exactly how it works.Rick Shine, Professor in Evolutionary Biology, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/370922015-02-03T19:03:59Z2015-02-03T19:03:59ZBuilding fences could stop cane toads in their tracks<figure><img src="https://images.theconversation.com/files/70866/original/image-20150202-13057-ube9q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cane toads are still spreading across northern Australia. </span> <span class="attribution"><span class="source">UNSW</span></span></figcaption></figure><p>Cane toads, introduced in 1935 to control cane beetles, have now spread across a huge swathe of Australia, from the Kimberley in northern Western Australia to northern New South Wales. </p>
<p>They’re <a href="http://www.environment.gov.au/system/files/resources/3f534390-51d6-45b5-8411-9a3913814027/files/cane-toad-fs.pdf">still spreading</a>, at a rate of between 40 and 60 km westward each year, and without management could eventually cover almost all of northern Australia. </p>
<p>Over the past few years, I and colleagues have been <a href="https://theconversation.com/close-100-man-made-lakes-to-stop-cane-toad-spread-study-11353">modelling</a> and testing the best way to control toads, particularly by fencing off man-made dams in inland Australia. In a paper published this week in the <a href="http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12390/abstract">Journal of Applied Ecology</a>, we show that fencing off dams can stop the spread of toads. </p>
<h2>Killing predators</h2>
<p>Cane toads have had dramatic effects on native predator populations across much of the continent, because native predators have no resistance to the toxins possessed by the toads. Consequently populations of goannas, freshwater crocodiles, some snakes and quolls have <a href="http://secure.environment.gov.au/biodiversity/invasive/publications/cane-toad/pubs/cane-toad-impact.pdf">crashed</a> following the toad invasion.</p>
<p>The importance of goannas as bushtucker has declined across much of northern Australia because of the decline in goanna numbers following the arrival of toads. </p>
<p>Perhaps surprisingly, toads also interfere with cleaning up cow pats. Dung beetles were introduced to Australia in the 1960s to help breakdown cattle dung, and reduce parasite loads in cattle because their dung burying activities disrupt the breeding-cycles of flies and parasitic worms. Dung beetle numbers and their effectiveness at breaking down cattle dung have <a href="http://onlinelibrary.wiley.com/doi/10.1111/aec.12028/abstract">declined</a> in some regions where toads have invaded.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70905/original/image-20150203-9187-ykf8oq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cane toads collect in vast numbers around inland waterways.</span>
<span class="attribution"><span class="source">UNSW</span></span>
</figcaption>
</figure>
<h2>Toad heaven</h2>
<p>Most of that area that cane toads will invade in Australia is arid or semi-arid bushland used for livestock grazing. In these areas, natural sources of water are normally sparse except after rain. </p>
<p>However, farmers have created thousands of dams at intervals of about 10 km to provide water for their livestock. Livestock normally do not drink from the dams. The dams are reservoirs for water that is pumped from underground-bores. They then provide water to livestock via troughs. These man-made sources of water each attract on average 600 toads and have vastly increased the area of Australia that the pests can invade. </p>
<p>Cane toads use the dams as refuges during the long dry periods that normally prevail in inland Australia. Toads disperse away from the dams after rain but must find another permanent water source to survive the next dry spell because they cannot survive without access to water for more than three days. </p>
<h2>Toad breaks</h2>
<p>We began our study in 2009 by fencing off dams in inland Australia. After two days the toads were eradicated from the area around the dams, and remained so for <a href="http://rspb.royalsocietypublishing.org/content/early/2011/02/17/rspb.2011.0032">at least two months</a>. </p>
<p>But the real test was if the fences stopped toads re-invading during the wet season. Our research published today shows that they do, suppressing toad numbers around dams for at least a year after they were fenced. </p>
<p>Our research shows that restricting toads access to water by fencing dams or using tanks made of plastic or steel as alternative type of reservoir to dams could work on a large scale to halt their march across the continent. If done strategically, fenced dams could act as “toad breaks” in much the same way as fire breaks work to slow bushfires. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70904/original/image-20150203-9198-1bi2vw9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fencing dams has cut toads off from their dry season refuges.</span>
<span class="attribution"><span class="source">UNSW</span></span>
</figcaption>
</figure>
<p>Restricting toads’ access to water could also be used in areas where toads have already invaded to reduce their numbers and their impacts. </p>
<p>Prior to our research, no effective way has been found to control cane toad numbers. Restricting toads’ access to water could massively reduce their numbers and impacts across most of the area that cane toads will invade.</p>
<p>However, it would not be a simple task or cheap. There are thousands of dams and our approach is only suitable for dry regions where natural sources of water are few. Mapping of dams and predictions of cane toad spread show that there are areas in Australia where excluding toads from water could be conducted strategically to have most effect.</p>
<p>For example, there is only a narrow corridor of land along the coast, through which cane toads could invade the Pilbara region of Western Australia. Keeping toads out of dams along this corridor could keep toads out of Pilbara. </p>
<p>Ultimately successful control of cane toads will require government agencies to work together with pastoralists and community groups to develop strategies for toad control and relieve the impacts that cane toads are having.</p><img src="https://counter.theconversation.com/content/37092/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Letnic receives funding from Hermon Slade Foundation.</span></em></p>Cane toads, introduced in 1935 to control cane beetles, have now spread across a huge swathe of Australia, from the Kimberley in northern Western Australia to northern New South Wales. They’re still spreading…Mike Letnic, Associate Professor, School of Biological, Earth and Environmental Sciences, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/312982014-10-01T02:09:31Z2014-10-01T02:09:31ZExplainer: how ‘biocontrol’ fights invasive species<figure><img src="https://images.theconversation.com/files/59057/original/jks9fdr7-1410823641.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rabbit numbers have been considerably reduced by the introduction of two viruses - Rabbit calicivirus and myxoma</span> <span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span></figcaption></figure><p><a href="http://www.timlow.com/books/feral-future">Australia’s “ferals”</a> — invasive alien plants, pests and diseases — are the largest bioeconomic threats to Australian agriculture. They also harm our natural ecosystems and biodiversity. Some, such as mosquitoes, also act as carriers of human diseases.</p>
<p>These invasive species cost Australian agriculture more than <a href="http://www.planthealthaustralia.com.au/wp-content/uploads/2012/12/National-Plant-Biosecurity-Strategy1.pdf">A$10 billion a year</a> — more or less what states and territories <a href="http://www.bitre.gov.au/publications/2011/files/is_040.pdf">spend on roads every year</a>. </p>
<p>One method of controlling invasive plants and pests — known as biological control, or “biocontrol"— is to use their own enemies against them. These "biocontrol agents” can be bacteria, fungi, viruses, or parasitic or predatory organisms, such as insects. </p>
<p>To find biocontrol agents, we travel to the native home of invasive species and search for suitable natural enemies. After extensive safety testing, they are introduced into Australia.</p>
<p>But do they work?</p>
<h2>Learning from the cane toad catastrophe</h2>
<p>Cane toads, which were introduced in 1935 to control cane beetles in Queensland’s sugar cane crops, are probably the most infamous <a href="http://www.canetoadsinoz.com/invasion.html">example of biocontrol going wrong in Australia</a>.</p>
<p>But Australia’s borders were more open back then. To protect against such harmful mistakes, Australia now has world-leading biosecurity import regulations and an effective quarantine system.</p>
<p>To be allowed entry into Australia, a candidate biocontrol agent must be assessed using <a href="http://www.daff.gov.au/ba/reviews/biological-control-agents/protocol_for_biological_control_agents/guidelines-introduction-exotic-bcas-weed-and-plants">internationally-recognised protocols</a>. This demonstrates that it will not pose unacceptable risks to domestic, agricultural, and native species.</p>
<h2>A cost-effective solution</h2>
<p>Other control methods, such as the use of poisons and mechanical removal, require continued reapplication. Many biocontrol agents of plants and insects, once established, are self-sustaining and don’t have to be reapplied. </p>
<p>Prickly pear is a <a href="http://www.daff.qld.gov.au/__data/assets/pdf_file/0014/55301/IPA-Prickly-Pear-Story-PP62.pdf">perfect success story of biocontrol</a>. The plant was introduced into Australia in the late 1770s and grown in a few areas of NSW and Queensland until it became invasive after rapidly spreading following the flood of 1893. Biocontrol was initiated in the early 1900s and the prickly pear moth, <em>Cactoblastis cactorum</em>, was introduced in 1926 from the pear’s native home in the Americas. <em>Cactoblastis</em> has been keeping prickly pear under control almost by itself to this day. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/59062/original/tvb3t5q8-1410824711.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cactoblastis moth larvae eating prickly pear.</span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<p>Since then, many more biocontrol agents have been introduced to control invasive plants. These include <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/348056/bpmg-biocontrol-impact-evaluation.pdf">mimosa in our top end, bridal creeper in southern Australia, parthenium in Queensland</a> and <a href="http://stca.tas.gov.au/weeds/wp-content/uploads/2010/01/weeds-pasture-field-crops-tasmania.pdf">ragwort in Tasmania</a>. </p>
<p>A <a href="http://www.southwestnrm.org.au/sites/default/files/uploads/ihub/page-ar-lacey-kl-2006-economic-impact-assessment-australian-weed-biological-control.pdf">series of cost-benefit analyses in 2006</a> revealed that for every dollar spent on biocontrol of invasive plants, agricultural industries and society benefited by A$23. This was due to increases in production, multi-billion dollar savings in control costs and benefits to human health.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/59058/original/89tg92bk-1410823714.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The invasive plant bridal creeper affected by its rust fungus.</span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<p>Biocontrol has also proven to be the only effective way to significantly reduce European rabbits across Australia. Myxoma virus was released in 1950, followed by rabbit calicivirus in 1995, causing regular disease outbreaks in wild rabbits. Together, they have kept rabbit numbers well below the devastating pre-1950s levels.</p>
<p>It’s estimated that the benefit of rabbit biocontrol to agriculture is worth more than <a href="http://www.feral.org.au/wp-content/uploads/2014/03/RabbitBiocontrol.pdf">A$70 billion</a>. This is the only example of a successful large-scale biocontrol program against a vertebrate pest anywhere in the world. </p>
<p>The initial costs of biocontrol programs are generally high. That’s because we have to find suitable candidate agents overseas, test them for safety in quarantine, and comply with regulations around release.</p>
<p>But once biocontrol agents are released and affect the invasive species across its range, follow up control costs are greatly reduced.</p>
<h2>Biocontrol is not a ‘silver bullet’</h2>
<p>Biocontrol will not solve all problems to do with invasive species. </p>
<p>Weather and climate can affect biocontrol agents, like all living organisms. These two factors can slow and even stop the agents building-up to sufficient levels to control the invasive species.</p>
<p>In the case of the two rabbit viruses, virus-host co-evolution has led to a decline in effectiveness of the viruses over time as they lost virulence and rabbits developed resistance to them. This is similar to how bacteria can develop resistance to antibiotics. As a result, we must continue to search for ways to counteract these effects. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/59060/original/xgpcdvbx-1410824120.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Crofton weed has overtaken hillsides of Lord Howe Island, but a new fungal disease will help control it.</span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<p>Like a multi-drug cocktail, biocontrol agents must often be used together to knock out an invasive species. And while biocontrol rarely completely eradicates an invasive species on its own, it may control it enough to be able to use other methods at a lower cost. </p>
<p>And just because we use biocontrol, it doesn’t mean we don’t need good farm practices and land management, such as bush restoration, to ensure the recovery of ecosystems affected by invasive species. </p>
<p>Biocontrol is unlikely to be the solution where invasive species are very closely related to species that we value — cats, for instance. Feral cats have recently been in the media as the <a href="https://theconversation.com/to-save-australias-mammals-we-need-a-change-of-heart-27423">greatest threat to Australia’s mammals</a>. But because they are the same species as the cherished family moggy, a biocontrol program would be highly controversial. </p>
<h2>New biocontrol programs</h2>
<p>The historic successes of biocontrol in Australia justify continued investment.
For widespread invasive species, there are no alternatives as cost-effective that work across the vast landscapes where feral species roam. </p>
<p>For example, the European carp pest makes up 90% of the fish biomass in the Murray Darling river system. The most promising option being developed for large-scale control is the carp-specific koi-herpes virus that is <a href="http://www.ecosmagazine.com/paper/EC12230.htm">in the final stages of testing</a> (to make sure the virus only targets carp). Its proposed release in Australia will soon be open for public debate. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/59061/original/6sgt45q9-1410824150.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">CSIRO has been testing in quarantine a new virus to control invasive carp.</span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<p>Another case is the recent <a href="http://www.csiro.au/Portals/Media/Biological-agent-closing-in-on-weedy-rampant-escapee.aspx">release of a rust fungus from Mexico</a> for the biocontrol of crofton weed in eastern Australia. This invasive plant smothers grazing systems and natural ecosystems, including <a href="http://csironewsblog.com/tag/crofton-weed/">on the hillsides of Lord Howe Island</a>, a World Heritage Area. The expectation is that this new highly-specific rust fungus will significantly contribute to control of this plant, the way other rust fungi have successfully done in the past against other invasive plants. </p>
<p>After 100 years of history in Australia, biocontrol should continue to have a bright future given it is the only approach that is environmentally-friendly, cheap and effective.</p><img src="https://counter.theconversation.com/content/31298/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Louise Morin receives funding primarily from Commonwealth, state and local governments, and rural Research and Development Corporations.</span></em></p><p class="fine-print"><em><span>Andy Sheppard receives funding from the Commonwealth Government and CSIRO contracted clients in the fields of environmental biosecurity and biological control </span></em></p><p class="fine-print"><em><span>Tanja Strive receives most of her funding from the Invasive Animals Cooperative research Centre.</span></em></p>Australia’s “ferals” — invasive alien plants, pests and diseases — are the largest bioeconomic threats to Australian agriculture. They also harm our natural ecosystems and biodiversity. Some, such as mosquitoes…Louise Morin, Group Leader, Biosecurity Flagship, CSIROAndy Sheppard, Research Director in the Biosecurity Flagship, CSIROTanja Strive, Project Leader/Team Leader, Biosecurity Flagship, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/198812013-11-07T19:33:32Z2013-11-07T19:33:32ZEveryone agreed: cane toads would be a winner for Australia<figure><img src="https://images.theconversation.com/files/34516/original/4chvqmtd-1383711425.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Two of millions of cane toads found across northern Australia.</span> <span class="attribution"><span class="source">Mark Lewis, Radio Pictures, Mullumbimby</span></span></figcaption></figure><p>When <a href="http://australianmuseum.net.au/Cane-Toad">cane toads</a> were released in Australia in 1935, they were the latest innovation in pest control, backed by a level of consensus support that a scientist could only dream of. So what went wrong?</p>
<p>Research <a href="http://purl.library.usyd.edu.au/sup/9781743323595">published today</a> reveals previously unreported government documents supporting the release of cane toads in Australia. </p>
<p>Cane toads built on successes in biological control, replaced pesticides like arsenic, pitch and copper, were supported by a published scientific paper, had international scientific peer review, were endorsed by Australia’s peak science body CSIR, championed by industry, promoted by the Queensland government and its premier, met quarantine regulations, were approved by the Commonwealth government and endorsed by the prime minister. </p>
<p>With cane toads, Australia thought it was on to a winner.</p>
<p>Today, a toxic cane toad slick rims northern Australia. The history of how that happened is important – especially if we’re to avoid making similar mistakes again.</p>
<p>Modern insecticides were developed in the 1940s. Before then, farmers and gardeners used predatory and parasitic wasps and flies, insect-eating birds, mongoose and toads to tackle pests. In the late 19th century, <a href="http://www.usda.gov/wps/portal/usda/usdahome">the US Department of Agriculture</a> elevated biological control to a science. Common practice was to release exotic agents of biological control untested into new environments.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=689&fit=crop&dpr=1 600w, https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=689&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=689&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=866&fit=crop&dpr=1 754w, https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=866&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/34489/original/3qq2gfzq-1383702814.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=866&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Le marche aux crapauds: a toad market in Paris, 1879.</span>
<span class="attribution"><span class="source">Le Journal illustré, 7 Septembre 1879</span></span>
</figcaption>
</figure>
<p>Toads had a pedigree. In 19th century France, toads were sold to gardeners at markets in Paris. French cane farmers carried giant toads from South America to control pests in their Caribbean sugar plantations. </p>
<p>In the early 20th century sugar cane scientists carried cane toads from Jamaica and Barbados to Puerto Rico, from there to Hawaii and then Queensland and Pacific Islands to control sugar cane pests. </p>
<p>The target pest for cane toads were species of scarab beetles whose larvae, grubs, browsed roots of sugar cane. The fatally flawed plan was that earthbound toads would control soil-dwelling grubs by somehow managing to eat airborne adults.</p>
<p>In Australia, biological control did have a precedent. The highly successful control of exotic prickly-pear cactus by the introduced Argentinian moth <em>Cactoblastis cactorum</em> in 1926 added to the consensus that biological control was the answer to the sugar industry’s woes.</p>
<p>There were few opponents to the introduction of the toad in Australia, and only one made his views public: retired former New South Wales Chief Entomologist Walter Froggatt. He forecast that cane toads</p>
<blockquote>
<p>may become as great a pest as the rabbit or [Prickly-pear] cactus.</p>
</blockquote>
<p>But Frogatt’s peers rebuked him. Eminent scientists branded his views “decidedly pessimistic”, “radical and biologically impossible apprehensions”, and accused him of holding “an incurable bias”. Today, some might label him a toad “denier”.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/34492/original/98nk6k8k-1383703325.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cyril Pemberton of the Hawaiian Sugar Planters’ Association took cane toads from Puerto Rico to Hawaii.</span>
<span class="attribution"><span class="source">Bishop Museum, Honolulu</span></span>
</figcaption>
</figure>
<p>In 1935, Queensland government entomologist Reg Mungomery carried cane toads from Hawaii and released them in northern Queensland. During the 1930s, cane toads were distributed throughout the Pacific Islands; many came from Hawaii and some from Queensland. </p>
<p>With the help of man, cane toads colonised some 138 territories and they now rank among the world’s most invasive species. </p>
<p>But the full extent of that impact in Australia only became obvious generations later. In 1975, 40 years after the toad’s release, the first survey of the awful impact of cane toads on Australian fauna was published by Mike Archer and Jeanette Covacevich of the Queensland Museum. And after 60 years, CSIRO first studied their interactions with northern Australian fauna. </p>
<p>More recently, Rick Shine, leader of <a href="http://www.canetoadsinoz.com/teambufo.html">Sydney University’s Team Bufo</a> concluded that although their impact has been profound it is <a href="http://www.jstor.org/stable/10.1086/655116">sometimes hard to separate from natural background variations</a> of little known ecosystems.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=771&fit=crop&dpr=1 600w, https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=771&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=771&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=969&fit=crop&dpr=1 754w, https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=969&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/34494/original/j2h24wnp-1383703695.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=969&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Reg Mungomery, who carried cane toads from Hawaii to Queensland in 1935.</span>
<span class="attribution"><span class="source">BSES Limited, Brisbane</span></span>
</figcaption>
</figure>
<p>Well-trained scientists from prestigious institutions helped spread the cane toad. By the criteria of the times, they were far from incompetent. It is simply wrong to think that current generations are qualitatively different and that such a calamitous biological event could not be repeated.</p>
<p>The catalyst was the consensus that restricted free enquiry. It led to oversimplification and misinformation. It prevented questioning of the suitability of cane toads.</p>
<p>Information was to hand in the observations of Queensland’s own scientists, but it was ignored. And there was no understanding of the toxicity that became the main problem for native fauna trying to eat cane toads.</p>
<p>Some would argue that consensus among scientists is an unnatural state for minds programmed to question sacred orthodoxies. But one thing is certain: we should be opening the doors of consensus to scientific scrutiny and critical debate, no matter what the issue, if we are to learn anything from the well-intentioned devastation wrought by the cane toad.</p><img src="https://counter.theconversation.com/content/19881/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nigel Turvey does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When cane toads were released in Australia in 1935, they were the latest innovation in pest control, backed by a level of consensus support that a scientist could only dream of. So what went wrong? Research…Nigel Turvey, Adjunct Professorial Fellow in Research Institute for Environment and Livelihoods , Charles Darwin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/164552013-07-30T04:27:44Z2013-07-30T04:27:44ZWhy cane toads give us small hope for climate change<figure><img src="https://images.theconversation.com/files/28219/original/qcd7p2b4-1375063340.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cane toads spread faster when they arrive in a new area.</span> <span class="attribution"><span class="source">Flickr/blundershot</span></span></figcaption></figure><p>Cane toads are one of the Australia’s most serious <a href="https://theconversation.com/the-toad-we-love-to-hate-11521">invasive species</a>, killing predators such as goannas, quolls and <a href="http://www.abc.net.au/news/2013-07-03/cane-toads-killing-dwarf-crocs-in-north-cdu-research/4796026">crocodiles</a> in the tropical north. We already know the toads are advancing from Queensland to the Kimberley. New research shows the toads may evolve to spread faster in new environments. But this may be good news for animals who have to move because of climate change.</p>
<p>So, how do we get from toads to climate?</p>
<h2>Hopping to it</h2>
<p>Most ecological theory starts with the assumption that a population of animals is stable in space: individuals and their offspring live in the same general area year after year. But, the reality is much messier: many populations are not stable. For example, invasive species expand their range as they spread.</p>
<p>As part of a long-term study by my University of Sydney-based “Team Bufo”, Greg Brown radio-tracked invasive cane toads as they first arrived at an area near Darwin, and continued to track newly-arriving toads over the next several years. Tom Lindstrom’s mathematical analysis of those radio-tracking results revealed a dramatic shift, <a href="http://www.pnas.org/content/early/2013/07/24/1303157110.abstract">published today</a> in the journal PNAS. </p>
<p>The first toads that arrived near Darwin were incredibly mobile, often moving more than one kilometre within a single night – but within a couple of years that rate had more than halved. The super-speediness seen at the invasion front is probably driven by evolutionary forces that come into play only at an expanding range edge, and are not seen in stable populations. <a href="https://theconversation.com/cane-and-able-how-superfit-toads-got-the-hop-on-evolution-512">Earlier studies</a> on the toad front had revealed these mechanisms, and the current work shows just how spectacular the acceleration can be.</p>
<p>That rapid decrease in mobility after the invasion front passes through means that studies on “normal” cane toads – that is, on animals from long-established populations – would underestimate the potential rate of movement. If we want to predict how quickly a species can expand its range, we need to look right at the expanding range edge.</p>
<p>Unfortunately, that’s logistically difficult, so most of our data on animal dispersal rates come from long-established, stable populations. As a result, we may be underestimating potential rates of population spread.</p>
<h2>Adapting to a changing world</h2>
<p>The problem doesn’t just relate to invasive species. Many species shift their ranges for other reasons. Climate change is rendering many areas unsuitable for the animals and plants that currently live there (for example, by becoming too hot or too dry). But at the same time it is creating those conditions somewhere nearby (in an area that previously may have been too cold or too wet).</p>
<p>If a species caught in this situation is to survive, individuals either must rapidly adapt to the new conditions, or move to the area that offers suitable conditions. The fast pace of climate change makes both of these options very tough to achieve, but not impossible.</p>
<p>Even in a species where individuals generally do not move about very much or very far, the process of expanding their range into a newly-suitable area will create an evolutionary pressure for faster and faster dispersal. The end result may be that many species will manage to shift their distributions more quickly than we would have guessed from the movement rates we can measure in existing stable populations. And perhaps that provides a glimmer of hope. </p><img src="https://counter.theconversation.com/content/16455/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Shine receives funding from the ARC. He does not work for, consult to or own shares in any company or organisation that would benefit from this article. </span></em></p>Cane toads are one of the Australia’s most serious invasive species, killing predators such as goannas, quolls and crocodiles in the tropical north. We already know the toads are advancing from Queensland…Rick Shine, Professor in Evolutionary Biology, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/115212013-02-10T23:51:33Z2013-02-10T23:51:33ZThe toad we love to hate<figure><img src="https://images.theconversation.com/files/19261/original/ky8cw8yv-1358308030.jpg?ixlib=rb-1.1.0&rect=0%2C243%2C1870%2C1562&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Australia’s best known pest.</span> <span class="attribution"><span class="source">AAP Image/Dave Hunt</span></span></figcaption></figure><p>For some unfathomable reason, cane toads stir the popular imagination. Most invasive species are simply not noticed by most of us, or, if they are, they are quickly assimilated into our mental landscape and forgotten. Who watches a honey bee flitting between dandelions and thinks “invasive species, both of them”? </p>
<p>Very few invasive species generate even a flicker of concern, and of those that do the cane toad is surely the one that attracts the most visceral of reactions: people either love them or hate them.</p>
<p>Why are toads here? What is their real impact on Australia’s native species? And what, if anything, can be done to stop them? Research over the last decade has revealed substantial new insights into these questions.</p>
<p>Toads were brought to Australia in 1935 by scientists working for the sugarcane industry. Australian toads had a long journey. They were originally native to South America, and came to Australia on a tide of enthusiasm for their ability to control beetle pests of sugarcane. This enthusiasm was ill-founded and naturally receded, but by then toads were already ashore in Australia as well as 22 other countries throughout the Caribbean and Pacific.</p>
<p>The introduction of toads in Australia occasioned little fanfare and generated little concern. Following the toads’ initial introduction in north Queensland, however, a lone but powerful voice (belonging to one Walter Froggat) raised fears that toads “may become as great a pest as the rabbit or the cactus” and that “there is no limit to their westward spread”. Froggat’s agitation caused an immediate ban to be placed on the further release of toads. This ban, in turn, caused the sugarcane lobby to exert political pressure. Within months word came <a href="cdupress.cdu.edu.au/HotTopics/.../HTT-1.1-Turvey-2009.pdf">from the Prime Minister’s Office</a> that the ban was to be lifted, and toads were immediately liberated as far afield as Mackay and Bundaberg. There was no stopping the sugar industry’s saviour now.</p>
<p>Since then, of course, Froggat’s predictions have proved prophetic. Toads now occupy more than 1.4 million square kilometres of the continent. Their range is continuous from northern NSW to the eastern Kimberley, and they continue to invade new areas. Sugarcane beetles are now controlled with insecticides.</p>
<p>Cane toads grow to be larger than any native Australian frog, but they also carry with them powerful cardio-active toxins that no native frog species produces; it is this toxin that inflicts the most environmental damage. There is little doubt that as toads spread they caused the death of countless thousands of native predators - quolls, goannas, crocodiles, snakes, and frogs - which, naive to the toads’ toxic nature mistook them for something edible.</p>
<p>Despite this carnage, however, toads have never, to the best of our knowledge, sent a native Australian species to extinction. There have certainly been local extinctions, particularly of quolls, goannas and some snake species, but in at least some places populations of native predators persist. How they do so is a fascinating story of its own, involving a diverse range of responses including <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560325/">rapid evolution</a> and <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2010.01802.x/full">learning</a>. Additionally, when toads remove goanna predators from a system, many other species (whose eggs and adults are preyed upon by goannas) may end up <a href="http://www.publish.csiro.au/?paper=WR05042">benefiting</a>.</p>
<p>Nonetheless, for some native predators - goannas, snakes, and quolls in particular - the arrival of toads is dire news indeed. We shouldn’t have introduced toads and we should do what we can to limit their impact. Unfortunately, the toads’ staggering reproductive potential (5,000 - 30,000 eggs at a sitting) makes them a daunting adversary. </p>
<p>To make matters worse, toads have <a href="http://www.jstor.org/discover/10.1086/588255?uid=3737536&uid=2132&uid=2&uid=70&uid=4&sid=21101533891223">evolved to become highly dispersive</a> during their invasion of northern Australia, where adult toads will regularly move 50km in a wet season. This combination of high reproductive rate and impressive dispersal ability makes controlling toads a formidable (some might say impossible) challenge. Compared to toads, rabbits, foxes and cats look easy.</p>
<p>Nonetheless, research on the basic ecology of toads has unearthed <a href="http://www.canetoadsinoz.com/">many surprising facts</a>, some of which can be bent towards toad control. Perhaps the most grisly of these is that toads are cannibalistic, and toad tadpoles (toadpoles) like nothing more than a snack of fresh toad egg. To find fresh toad eggs, toadpoles home in on the very same toxin that makes toads so dangerous to our native predators. Thus, a simple yabby trap, baited with soluble toad toxin, will rapidly catch <a href="http://www.canetoadsinoz.com/cane_toad_tadpole_control.html">thousands of toadpoles</a> but won’t attract anything else.</p>
<p>Local control strategies such as this, when executed at the right place, can have profound benefits. By denying toads access to <a href="https://theconversation.com/close-100-man-made-lakes-to-stop-cane-toad-spread-study-11353">100 artificial waterbodies</a> in the right place, for example, we can totally prevent the natural spread of toads into Western Australia’s Pilbara region. Doing so would prevent the natural spread of toads into 268,000 square kilometres of suitable habitat (an area the size of Great Britain) and help secure some of the last healthy mainland populations of quolls and goannas that are currently unaffected by toads.</p>
<p>Love them or hate them, toads are here to stay. Their biodiversity impact is probably less than the public imagination would have it, but also substantially more than we would like. </p>
<p>New strategies, built off basic research into the ecology of toads, provide new means of reducing their local abundance, and even of halting their spread across northern Australia. Executing these strategies will require substantial participation and interest from the public. Not the kind of interest one might get for proposals to control dandelions, but interest of the more intense and visceral kind; the kind of interest aroused by toads.</p><img src="https://counter.theconversation.com/content/11521/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ben Phillips receives funding from the Australian Research Council.</span></em></p>For some unfathomable reason, cane toads stir the popular imagination. Most invasive species are simply not noticed by most of us, or, if they are, they are quickly assimilated into our mental landscape…Ben Phillips, Evolutionary Ecologist, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/15452011-06-02T03:57:43Z2011-06-02T03:57:43ZCane toad movie says put aside prejudice - in 3D<figure><img src="https://images.theconversation.com/files/1454/original/cane_toads_film.jpg?ixlib=rb-1.1.0&rect=11%2C502%2C1690%2C1995&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hated enemy or part of the landscape?</span> <span class="attribution"><span class="source">Radio Pictures</span></span></figcaption></figure><p>Every night under cover of darkness an advancing wall of toads heads west. Rather than winding through the bush, the toads march straight down the highway, ignoring the official border signs. </p>
<p>Meanwhile, on the Western Australian side of the border, perch gangs of volunteers from the Kimberley Toad Busters awaiting the toad arrivals. The border gangs capture the creatures in plastic bags, gas them, then measure, weigh and tag them before dumping them into mass graves. </p>
<p>Futile efforts in the face of the so-called “unending hordes”, “the invasion front”, “public enemy number one”, or just plain old “vermin”? </p>
<p>Rewind 23 years to 1988 to a scene you may remember. A Queensland Kombi driver weaves purposefully all over the road, his van leaving squashed animals in its wake. “Pop” goes each toad as tyre strikes flesh, while he describes utter revulsion for this amphibian and his love of native wildlife. </p>
<p></p><figure><p></p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OtMtIItimjQ?wmode=transparent&start=152" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Both these scenes, captured in Mark Lewis’s first and second cane toad films, <a href="http://www.imdb.com/title/tt0130529/">Cane Toads: An Unnatural History</a> (1988) and <a href="http://www.canetoadstheconquest.com/">Cane Toads: The Conquest</a> (opens June 2), are poignant images of human futility in the face of rapid animal evolution. </p>
<p>The brazen success of <em>bufo marinus</em> in the Australian environment – the way it has assimilated, hybridized and utterly thrived - undermines the notion of human supremacy over nature. </p>
<p>While our capacity for progress seems limitless, says one scientist in <em>The Conquest</em>, we still haven’t found a way to combat the toad. Despite vocal protests from locals upon their arrival in a new area, and events like the annual “toad day out”, the reptile is now firmly entrenched in many parts of the country as well as in the Australian human (and probably animal) psyche. </p>
<p>The problem began in 1935 when 102 toads were imported from Hawaii to save Queensland cane crops from devastation by the greyback beetle. Given the differing life-cycles of the grub and the toad, and the fact that toads can’t fly – yet – their introduction is considered by most scientists to be an environmental blunder of monumental proportions. </p>
<p>Some estimates put their population at around 1.5 billion. According to Adrian Franklin, author of <em>Animal Nation: the true story of animals in Australia</em>, the toad was introduced at a time when economic value was upmost and wildlife impact an afterthought. </p>
<p>But the blunder demonstrates the dangers of too simplistic a view of animal ecology as being fixed as opposed to being adaptive and dynamic. </p>
<p>Thankfully the dire prediction made in the first film by a young Dr Mike Archer — now Professor and (former) Dean of Science at UNSW — that most of the big carnivores would be wiped out creating a monoculture, hasn’t materialized. In a scene worthy of an Oscar, an anguished and effusive Archer describes the tortured death his adored pet quoll endures after feasting on <em>bufo marinus</em>.</p>
<p></p><figure><p></p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/p8MZtzEoiTY?wmode=transparent&start=176" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Remarkably within the space of 70 years some species of animals that were close to extinction 30 years ago because of the cane toad have adapted to their poison and even replenished their numbers. </p>
<p>As far as <a href="http://theconversation.com/profiles/rick-shine-595">Professor Rick Shine</a> (one of the foremost researchers on the toad based at Sydney University’s Institute for Sustainable Solutions) knows, no species have become extinct as a result of the introduction of the cane toads to Australia. But how the native animals evolve to accommodate the toad continues to baffle evolutionary ecologists. </p>
<p><em>Bufo marinus</em>’s exceptional evolution and behavior also fascinates Australian scientists. Originally they believed the toads wouldn’t be able to migrate across the vast northern river systems nor endure the region’s long dry. Yet the toads have rapidly mutated into remarkable dispersal machines, claims Shine. </p>
<p>Having evolved the longest back legs, the <a href="http://theconversation.com/cane-and-able-how-superfit-toads-got-the-hop-on-evolution-512">swiftest then reproduce</a> on the “frontline”. </p>
<p>Exploiting the paths of least resistance – multiple corridors of Northern Territory roads – enables the athletic toad to penetrate further and faster into the NT and WA. Shine calls this the “Olympic village effect”. </p>
<p>Even Shine’s research career reveals adaptations because of the toad. He began as a reptile expert, focusing on the evolution of crocodiles in the NT. The he noticed his research subjects dying in vast numbers so he started studying the maligned villain killing his crocodiles. </p>
<p>At a recent community screening of the 1988 film at Petersham Bowling Club in Sydney, one audience member asked Shine why Australia boasts all the foremost <em>bufo marinus</em> experts. Shine’s laconic response: “Because no other country really cares about them”. </p>
<p>Cane toads have attracted significant Australian research interest and millions of dollars in grants over the years. The CSIRO once had an $11m grant to genetically engineer a virus to restrict their numbers. </p>
<p>This was abandoned when it was realized that with strong winds this virus would drift over mainland Indonesia, home to many vulnerable native toad populations. Native toads of Indonesia are vital to their own ecosystems, controlling insects like malaria-born mosquitoes. </p>
<p>While Shine agrees that there is a place for intervention into nature when it comes to toads, he thinks that this should be done humanely and as “naturally” as possible. </p>
<p><em>The Conquest</em> is a more sophisticated film than its predecessor and often conjures a sense of empathy for the toad. But the satirical and absurdist humour that made the first film a “cult classic”, is still palpable. </p>
<p>During question time at the Sydney Film Festival screening last year Mark Lewis played down the film’s technological achievements - as Australia’s first 3D film - and seemed prouder that <em>The Conquest</em> featured the world’s first dog hallucination scene. Dobbie, a canine crossbreed, has become addicted to licking toads for their hallucinatory high. Even the film’s poster carries a warning: “licking this toad can be hazardous to your health”. </p>
<p>Cornell historian <a href="http://en.wikipedia.org/wiki/Dominick_LaCapra">Dominick La Capra</a> has claimed that the 21st century will be the century of the animal. Cane toads have provoked scientists to re-think their understanding of animals’ evolutionary and adaptive capacities. Mark Lewis’s film is a humorous but at times melancholic plea to re-think our relationship with the much-maligned toad.</p></figure></figure><img src="https://counter.theconversation.com/content/1545/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Catherine Simpson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Every night under cover of darkness an advancing wall of toads heads west. Rather than winding through the bush, the toads march straight down the highway, ignoring the official border signs. Meanwhile…Catherine Simpson, Senior Lecturer in Science Communication, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/5122011-04-12T07:01:16Z2011-04-12T07:01:16ZCane and able – how superfit toads got the hop on evolution<figure><img src="https://images.theconversation.com/files/465/original/canetoad.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Do cane toads add something new to 'natural selection'?</span> <span class="attribution"><span class="source">manda/Flickr</span></span></figcaption></figure><p>Some 150 years ago, Charles Darwin proposed a mechanism for evolutionary change; but is there something beyond natural selection driving evolution? </p>
<p>My colleagues and I think so, and we believe it has come from an unlikely source – the much-maligned cane toad. </p>
<p>These large poisonous frogs from Central and South America are spreading through tropical Australia at an increasing rate. </p>
<p>When they were first released in north-eastern Queensland in 1935 (in a naïve attempt to control beetles in sugar cane fields), the toads began spreading at about ten to 15 kilometres a year. </p>
<p>But they have accelerated ever since, and the current invasion front is sweeping into Western Australia at some 60 kilometres a year.</p>
<p>Why are the toads moving so much faster now than they did 70 years ago? It’s due to genetic changes. </p>
<p>The offspring of “invasion-front” toads are also fast movers, even if they’ve been raised in captivity. So why have the toads evolved to be long-distance runners instead of couch potatoes?</p>
<p>The orthodox explanation for this change would be natural selection – that is, faster-dispersing toads have survived better, or produced more offspring, than their slower counterparts. </p>
<p>That process could result in faster and faster toads through the generations, in the usual Darwinian view.</p>
<p>But we think something else is going on. </p>
<p>It seems there may be more disadvantages than advantages to a toad that disperses quickly. We’ve radio-tracked a lot of toads, and have found that the fastest-dispersers are the ones most likely to be found and eaten by a predator. </p>
<p>Also, the frontline toads often experience severe arthritis in their spines because of the pressures placed upon them by moving so quickly and so often. </p>
<p>And the frontline toads don’t breed very often. </p>
<p>None of this seems to fit the idea of faster dispersal evolving because it confers a benefit to a toad’s survival and reproduction – that is, natural selection.</p>
<p>Instead, we think the evolution of cane toad dispersal rates is a consequence of genes for rapid movement sorting out through space. </p>
<p>Any mutation that makes a toad move faster is likely to end up at the frontline; and any mutation that slows a toad down, or makes it move around in circles, will end up far behind the front. </p>
<p>So genes for moving fast, moving every night and moving in a straight line accumulate at the invasion front – with the result that the frontline moves quicker and quicker.</p>
<p>This process never requires any individual toad to benefit from faster dispersal, so it’s not natural selection, but something else entirely.</p>
<p>What is this mysterious new non-Darwinian process? We’ve called it “spatial sorting”. It’s not as important as natural selection, because it only works for certain traits (those that affect dispersal rate) and in some situations (a range-expanding species). </p>
<p>But under those limited conditions, it can be really important. The toads are telling us that natural selection is not the only evolutionary process out there in this complicated world.</p>
<p> </p>
<p><em>Read the full PNAS paper describing this idea <a href="http://www.pnas.org/content/108/14/5708.full.pdf+html?sid=fe26a89f-3a26-4dec-abd0-ffc76813d75a">here</a></em>.</p><img src="https://counter.theconversation.com/content/512/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Shine receives funding from the Australian Research Council.</span></em></p>Some 150 years ago, Charles Darwin proposed a mechanism for evolutionary change; but is there something beyond natural selection driving evolution? My colleagues and I think so, and we believe it has come…Rick Shine, Professor in Evolutionary Biology, University of SydneyLicensed as Creative Commons – attribution, no derivatives.