tag:theconversation.com,2011:/africa/topics/rodent-6040/articlesRodent – The Conversation2023-12-04T17:26:43Ztag:theconversation.com,2011:article/2168462023-12-04T17:26:43Z2023-12-04T17:26:43ZRats are more human than you think – and they certainly like being around us<figure><img src="https://images.theconversation.com/files/561844/original/file-20231127-29-v6hvrg.jpg?ixlib=rb-1.1.0&rect=7%2C14%2C2488%2C1646&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/two-cute-curious-brown-rats-looking-295110965">Gallinago_media/Shutterstock</a></span></figcaption></figure><p>Rats have a somewhat unfortunate tendency to enjoy living where people live. That’s how a biologist tried to explain people’s hatred for the rodents in a television <a href="https://www.svt.se/nyheter/lokalt/skane/tre-fragor-om-darfor-gnager-rattorna-sonder-din-bil">news feature about rats</a> gnawing electrical cables in parked cars in the southern Swedish town of Malmö. </p>
<p>The brown rat, <em>Rattus norvegicus</em>, is one of the species best adapted to modern society. These rats have followed humans around the world to become one of the most abundant mammals, spreading from their native distribution in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8214441/">northern China</a> and Mongolia and reaching Europe <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2016.1762">in the 1500s</a>, possibly even earlier. Black rats, however, arrived in Europe as early as the <a href="https://www.york.ac.uk/news-and-events/news/2022/research/black-rat-europe/">1st century AD</a>. </p>
<p>Today almost all wild brown rats are <a href="https://davidrousefaicp.com/synanthropic-species-why-are-they-important-to-our-future/">synanthropic</a>, meaning they live in close association with humans, eating our leftovers and using human structures for shelter. The relationship between rats and humans is one of commensalism, a word derived from the Latin term “commensal”, meaning “<a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/commensalism#:%7E:text=Literally%2C%20the%20term%20means%20%E2%80%9Ceating,two%20partners%20can%20survive%20independently.">eating at the same table</a>”. </p>
<p>Throughout the centuries, rats have been cast as humanity’s dark shadow. Rats have had an enormous impact on human civilisation, not least through the spread of diseases. They have long been associated with <a href="https://archive.org/details/dictionary-of-mythology-folklore-and-symbols-vols-1-3-gertrude-jobes-1962">dirt, death and destruction</a>. In medieval Europe people loathed rats for their so-called brutishness, <a href="https://press.uchicago.edu/ucp/books/book/distributed/R/bo3616680.html">seemingly limitless sexual appetite</a> and fecundity. But their huge numbers and adaptability mirrors humans’ evolutionary success. </p>
<p>They have <a href="https://www.sciencedirect.com/science/article/abs/pii/S0160932705000785">spread with wars</a> and European imperialism to colonised territories in the Americas as well as Africa and Australia. Rats <a href="http://0-blogs.biomedcentral.com.brum.beds.ac.uk/bugbitten/2014/11/10/parasites-and-diseases-in-the-trenches-of-world-war-i/">thrive in the trenches</a> of <a href="https://www.businessinsider.com/rats-in-russian-trenches-front-line-add-to-disgusting-conditions-2023-10?r=US&IR=T">modern warfare</a> even today. </p>
<h2>A social and empathetic animal</h2>
<p>Real rats are far from the despicable creatures they often are made out to be. Several studies have shown that rats have powerful empathy. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/TNKbDTcDsqw?wmode=transparent&start=66" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>These animals can share the emotional state of others, which in psychology is called emotional contagion. <a href="https://www.sciencedirect.com/science/article/pii/S1364661322001115">Research has shown</a> that when a rat sees another rat in distress, the neural structures activated in that rat’s brain closely resembles those activated in humans brains when feeling empathy for pain of others. </p>
<p><a href="https://www.washingtonpost.com/national/health-science/a-new-model-of-empathy-the-rat/2011/12/08/gIQAAx0jfO_story.html">One experiment showed</a> that rats will release a fellow rat from an unpleasant cage even if they are not rewarded for it. And if given chocolate treats afterwards, the free rat would usually save at least one treat for the former captive. </p>
<p>This selfless behaviour comes from rats’ socially complex lives in family groups of multiple generations. They form lifelong bonds with other rats and share socially learned skills, such as foraging techniques, across generations. This means rats have a <a href="https://elifesciences.org/articles/54020">form of culture</a>. </p>
<p><a href="https://www.theguardian.com/science/2023/nov/02/rats-may-have-power-imagination-research">A study from 2023</a> even showed that rats can imagine places and things that aren’t in front of them at the time. In experiments rats were shown to <a href="https://www.science.org/doi/10.1126/science.adh5206">navigate a space</a> in their thoughts, that they have previously explored. As in the studies of empathy, researchers demonstrated this by comparing the regions in the rat’s brains that were activated to those that are activated when humans think about navigating their way through places they have visited.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/FtjI5nDlrDg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>This ability to imagine also suggests that rats have a sense of past and future. </p>
<h2>Living and dying with rats</h2>
<p>With this in mind, human ways of dealing with rats seem cruel. The most common chemical method for rat control <a href="https://www.pestprooflondon.co.uk/rat-poison/">is anticoagulants</a>, which cause fatal internal bleeding one to two weeks after a rat eats the poison. Since rats are both socially intelligent and cautious, they prefer to sample unfamiliar food and then wait to see if it makes them or other rats sick. </p>
<p>It’s called <a href="https://www.sciencedirect.com/science/article/abs/pii/0168159189900373">poison shyness</a>. With anticoagulants however, the time between consumption of the bait and the rat dying is so long that they don’t usually associate it with their feeding habits. </p>
<p>The human motivation for learning about rats has often been the desire to kill them. The foremost experts in wild rat behaviour are their exterminators. And yet, current methods for controlling wild rat populations are not very effective.</p>
<p>Some rats have <a href="https://www.pestcontrol.basf.co.uk/Documents/Training/Anticolagulant-Resistance-in-the-UK.pdf?1647246881707">developed resistance to the poisons</a> and are able to eat it and survive. Trapping them is notoriously difficult, and they often recolonise the territory from which they have been removed.</p>
<p><a href="https://www.icup.org.uk/media/ntwhyvrt/icup466.pdf">Global urbanisation</a> is probably only going to bring humans into <a href="https://www.pnas.org/doi/10.1073/pnas.2112341119#:%7E:text=As%20urbanization%20has%20intensified%20globally,spaces%20(3%E2%80%935).">closer contact with rats</a>, and killing rats the way it is done today isn’t ethical. </p>
<figure class="align-center ">
<img alt="Rat poking its head up from a black iron hatch/" src="https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562400/original/file-20231129-21-x68ffx.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">It’s time to consider if there are less violent ways of living alongside rats.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cute-gray-rat-looking-out-hole-1148729435">TashaBubo/Shutterstock</a></span>
</figcaption>
</figure>
<p>Instead, we should consider other strategies, like the ones explored by the <a href="https://www.helsinki.fi/en/projects/urban-rats">Urban Rat Project</a> at the University of Helsinki. Here researchers from different disciplines are trying to get a deeper understanding of conflicts between rats and humans. They are studying both species and their interactions, in hope of a future with less bloody human-rat relations.
The project has spotted that places in urban areas where people feed birds tend to attract rats as well – which people then try to eradicate using poison or traps.</p>
<p>Research has also suggested <a href="https://helda.helsinki.fi/items/36d81d1e-9d71-41e2-b694-6ae88a8b4be5">that with increased knowledge</a> about rats and their behaviour people tend to develop a more positive attitude towards them. So more knowledge of wild rats’ social behaviour is needed. And humans need to manage their own behaviour to avoid conflict with rats. </p>
<p>A good place to start would be reducing food waste and stop leaving leftovers out unsecured. Less rats around human food sources, for example, and more knowledge about their behaviour would mean a lower risk of diseases spreading from rats to humans, as well as from humans to rats. </p>
<p>Humanity’s future is with the rat, a social and empathetic animal. So it’s time we understood our shadows.</p><img src="https://counter.theconversation.com/content/216846/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tobias Linné 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>Rats are well known to cause problems for humans. But we need a new approach to our relationship with them.Tobias Linné, Assistant Professor in Media and Communication Studies, Lund UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1595692021-10-04T14:53:14Z2021-10-04T14:53:14ZCreature that inspired Pikachu is being blamed for an ecological crisis – but it may be innocent<p>Known as the water tower of Asia, the Tibetan Plateau is where the mighty Yellow, Yangtze and Mekong rivers begin as tiny trickles. The plateau is also sometimes referred to as the roof of the world – a vast plain raised 4,500 metres above sea level and surrounded on all sides by imposing mountain ranges, one of which includes Mount Everest. For the 1.4 billion people living downstream, the plateau is an irreplaceable source of fresh water.</p>
<p>For the nomadic people who live here, the plateau is their livelihood. But half of the meadows in the region are at risk of <a href="https://link.springer.com/article/10.1007/s12665-013-2338-7">turning into black soil</a> – the eventual fate of degraded alpine meadows. Local communities who rely on the plateau’s pastures to graze their cattle and sheep often blame pika, a small, rabbit-like mammal on which the Pokemon character Pikachu is based. But is this really fair?</p>
<p>Black soil patches occur when plants and grass turf have been completely lost from a meadow, and their emergence can be accelerated by the burrowing of plateau pikas. Tibetan nomads think the arrival of pikas from degraded pastures several kilometres away heralds the downfall of their own pasture. Traditional beliefs maintain that pikas arrive riding on the backs of snow finches, but Buddhist thought discourages nomads from killing them. Instead, they often invite monks to say pika-expelling prayers.</p>
<p>Despite their certainty, the pika’s role in the degradation of the plateau’s pastures is actually rather complex, as <a href="https://link.springer.com/article/10.1007/s10980-021-01191-0">my research reveals</a>. Far from condemning this tiny herbivore, the evidence points to a greater villain: recent changes to how the land here is managed.</p>
<h2>Pikas in the dock</h2>
<p>Plateau pikas are timid animals and prefer to live in grassland that is less than 10cm high. Short-grass pastures with bare soil patches allow them to better see their predators, such as <a href="https://ebird.org/species/uplbuz1">the upland buzzard</a>.</p>
<p>Pikas also have similar taste in plants to the Tibetan Plateau’s <a href="https://www.theguardian.com/environment/2021/feb/04/yak-politics-tibetans-vegetarian-dilemma-amid-china-meat-boom">14 million yaks</a> – the long-haired domestic cattle which share their pasture and typically feed within ten metres of their burrows. Once pikas move into an area of pasture, their feeding reduces the amount of palatable plants, so yaks graze neighbouring areas of untouched taller grass. This grazing then creates better habitats for pikas, especially during the summer when the average family size of pikas <a href="https://academic.oup.com/beheco/article/9/6/622/336181?login=true">swells</a>. </p>
<figure class="align-center ">
<img alt="A herd of shaggy cattle with horns spread out on an undulating grassland." src="https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424447/original/file-20211004-27-rvr69n.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">Yaks inadvertently create ideal habitats for pikas by grazing tall grass.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/yaks-tibetan-plateau-160431626">Martinez de la Varga/Shutterstock</a></span>
</figcaption>
</figure>
<p>Plateau pikas can produce up to five litters a year, so the grazing intensity of domestic yaks has to be controlled to prevent them making lots of habitat well-suited to pika, to limit how fast and high pika populations grow.</p>
<p>But herding livestock is time consuming, and this kind of land management is not always in place. In many parts of the plateau’s meadow regions, livestock numbers peaked in the 1980s and 1990s, when they were two to three times higher than they were in the early 1960s. Rangeland once held in common was parcelled up to individual households in the 1990s. By the early 2000s, now-sedentary nomads began installing metal fences along the boundaries of their land to prevent their livestock from wandering off and to help keep them safe from wolves. This meant shepherds no longer had to watch over and herd their livestock.</p>
<p>Confined inside fences, however, yak and sheep can graze wherever they like, mowing and trampling the grass. When pikas are nearby, it’s easy for them to cross over fences and disperse into these overgrazed patches. The result of nomads being unable to move their livestock as freely as before is the intensive grazing that has provided the ideal environment for these small mammals to thrive in.</p>
<h2>The verdict</h2>
<p>The plateau provides a home to around <a href="https://www.jstor.org/stable/26799089?seq=1#metadata_info_tab_contents">6 million</a> herders. Expanding black soil patches on the grassland threaten their livelihood and, while pika numbers continue to increase, the scientific community is divided over the best response. </p>
<p>Some believe the little creatures should be culled, while others argue they play a critical role at the bottom of the food chain, supporting populations of foxes, weasels, pole cats and birds of prey, and so must be protected.</p>
<p>The plateau pika does play a central role in this crisis, but land-use changes among local nomads are the real issue. Keeping grass higher than 10cm would mean less food for yaks, and most nomads can’t afford the shortfall in meat, butter and milk they derive from their livestock. Government subsidies which are more accurately tied to each family’s herd size could compensate nomads for leaving areas free from grazing.</p>
<p>The key to saving the plateau’s meadows, then, is not to demonise the pika, but to develop a culturally acceptable solution that both controls this wild mammal’s populations and allows pastoral nomads to continue making a living.</p><img src="https://counter.theconversation.com/content/159569/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Li Li receives funding from China Postdoctoral Science Foundation and National Key Research and Development Program of China. She is currently the consultant for the Grassland Conservation Project of Shan Shui Conservation Center in Beijing. </span></em></p>The electric Pokemon’s real-life muse is charged with degrading the vast meadows of the Tibetan Plateau.Li Li, Assistant Professor of Landscape Ecology, Xi'an Jiaotong-Liverpool UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1609952021-05-20T19:58:19Z2021-05-20T19:58:19ZMouse plague: bromadiolone will obliterate mice, but it’ll poison eagles, snakes and owls, too<figure><img src="https://images.theconversation.com/files/401185/original/file-20210518-15-1z5t01.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C5455%2C3289&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Masked owl (_Tyto novaehollandiae_), one of many birds of prey at great risk of secondary poisoning </span> <span class="attribution"><span class="source">Belinda Davis</span>, <span class="license">Author provided</span></span></figcaption></figure><p>It’s the smell that hits you first. The scent of urine and decomposing bodies. Then you notice other signs: scuttles and squeaks, small dead bodies leaking blood, tails sticking out of hubcaps. </p>
<p>If you’ve lived through a <a href="https://theconversation.com/no-one-ever-forgets-living-through-a-mouse-plague-the-dystopia-facing-australian-rural-communities-explained-by-an-expert-159339">mouse plague</a>, you’ve seen this, and smelled the stench of mice dying of poison baits.</p>
<p>As a desperate measure to help combat the mouse plague devastating rural communities across New South Wales, the state government yesterday <a href="https://www.canberratimes.com.au/story/7260799/nsw-secures-mice-killer-poison-for-farmers/?cs=14231">secured 5,000 litres of bromadiolone</a>. This is a bait that’s usually illegal to roll out at the proposed scale.</p>
<p>This is a bad idea. While bromadiolone effectively kills mice, it also travels up the food chain to poison predators who eat the mice, and other species. And these predators, from <a href="https://www.sciencedirect.com/science/article/abs/pii/S0048969721027443?via%3Dihub">wedge-tailed eagles</a> to goannas, are coming out in droves to feast on their abundant prey. </p>
<h2>When your prey is everywhere</h2>
<p>Animal plagues in Australia are fuelled by the “boom and bust” of rainfall. </p>
<p>We have natural, flood-driven population explosions of the native long-haired rat, with accompanying booms of letter-winged kites, their predator. We also have locust plagues when the conditions are right, leading to antechinus or mice plagues which eat the locusts. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1394622017920397329"}"></div></p>
<p><a href="https://theconversation.com/no-one-ever-forgets-living-through-a-mouse-plague-the-dystopia-facing-australian-rural-communities-explained-by-an-expert-159339">Since at least the late 1800s</a>, we’ve had terrible plagues of the introduced house mouse (<em>Mus musculus</em>). But rarely has it been this bad, with conditions currently seeming worse than the last plague in 2011, which caused over <a href="https://grdc.com.au/resources-and-publications/groundcover/ground-cover-issue-95-november-december-2011/plague-threat-pushes-mouse-bait-changes">A$200 million</a> in crop damage alone.</p>
<p>High numbers of birds of prey — nankeen kestrels, black-shouldered kites and barn owls — are often <a href="https://www.publish.csiro.au/mu/pdf/MU9820227">reported</a> feasting on plague mice. </p>
<p>Snakes, goannas, native carnivores such as quolls, and feral cats and foxes, also take advantage of the abundant food. Pets, especially cats and some dogs, are highly likely to consume mice under these conditions, too.</p>
<h2>Poisoning the food web</h2>
<p>Laying out poison baits is one way people try to end mouse infestations and plagues. So-called “anticoagulant rodenticides” are divided into first and second generations, based on when they were first synthesised and the differences in potency. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Wedge-tailed eagle" src="https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/401782/original/file-20210520-13-4kg4l3.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"></a>
<figcaption>
<span class="caption">Wedge-tailed eagles are among the predators that take advantage of the house mouse plague.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Second generation anticoagulant rodenticides have higher <a href="https://pubmed.ncbi.nlm.nih.gov/21481471/">toxicities</a> than first generation, and are lethal after a single feed. First generation rodenticides, on the other hand, require rodents to feed on them for consecutive days to be <a href="http://pesticideresearch.com/site/docs/bulletins/EPAComparisonRodenticideRisks.pdf">lethal</a>.</p>
<p>But mouse-eating predators are highly exposed to second generation rodenticides. For most animal species, the lethal doses of rodenticide aren’t yet known. </p>
<p>A <a href="https://www.sciencedirect.com/science/article/abs/pii/S0048969718312336?via%3Dihub">scientific review</a> from 2018 documented the poisoning of 31 bird, five mammal and one reptile species. Second generation aniticoaugulant rodenticides were implicated in the death of these animals.</p>
<p>Our <a href="https://www.sciencedirect.com/science/article/abs/pii/S0048969720317319?dgcid=coauthor">research</a> from 2020 found urban reptiles are highly exposed to second generation rodenticides, too. This includes mouse-eating snakes, called dugites, which had up to five different rodent poisons in them. </p>
<p>We also found poisons in frog-eating tiger snakes, and in omnivorous bobtail skinks which eat fruit, vegetation and snails. This is even more concerning because it shows how second generation rodenticides can saturate the entire foodweb, affecting everything from <a href="https://www.sciencedirect.com/science/article/pii/S0048969717321150">slugs</a> to <a href="https://link.springer.com/article/10.1007/s11356-018-1385-80">fish</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bobtail skink" src="https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/401783/original/file-20210520-17-jzhuek.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">Bobtail skinks don’t eat poisoned mice, but they’ve still been found with poison in their systems.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Bromadiolone is particularly dangerous, even to humans</h2>
<p>The NSW government secured bromadiolone baits as part of its <a href="https://www.nsw.gov.au/media-releases/50-million-support-package-to-help-regional-communities-combat-mouse-plague">$50 million mouse plague support package</a> for regional communities. </p>
<p>Five thousand litres of the poison <a href="https://www.canberratimes.com.au/story/7260799/nsw-secures-mice-killer-poison-for-farmers/?cs=14231">can treat</a> around 95 tonnes of grain, and the government will provide it for free to primary producers once federal authorities approve its use. </p>
<p>Bromadiolone is usually restricted to use in and around buildings. But given the widespread impacts on wildlife, using bromadiolone at the proposed scale will do more harm than good. </p>
<p>Past research on bromadiolone has shown residues persist for up to 135 days in the carcasses of <a href="https://www.sciencedirect.com/science/article/abs/pii/S0048969708009030">voles</a> (another rodent species). In international studies, bromadiolone has been <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6395208/">found</a> in the livers of a host of birds of prey, including a range of owl species, red kites, sparrowhawks and golden eagles. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Flock of chickens" src="https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/401784/original/file-20210520-13-17tyigs.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">Humans can be exposed, too, by eating the eggs of chickens that ate the mice.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>And it’s not just a problem for wildlife, <a href="https://www.tandfonline.com/doi/full/10.1080/15563650600795966">humans</a> are also at risk of exposure. For example, we can get exposed from eating eggs from chickens that feed on poisoned mice, or more directly from eating other animals that may have ingested poisoned mice. </p>
<p>A <a href="https://journals.sagepub.com/doi/full/10.1177/1040638713501510">2013 study</a> looked at chicken eggs for human consumption, and detected bromadiolone in eggs between five and 14 days after the chicken ingested the poison. It’s not yet clear how many of these eggs we’d have to eat for us to get sick.</p>
<h2>So what are the alternatives?</h2>
<p>There are highly effective first generation rodenticides that provide viable solutions for managing mouse plagues. They may take a little longer to kill mice, but the upshot is they don’t stick around in the environment. A 2020 study found house mice in Perth <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236234">didn’t have genetic resistance</a> to first generation rodenticides, which suggests they’re effectively lethal. </p>
<p>Another approach has been to use zinc phosphide, a poison which is unlikely to secondarily poison other animals that eat the poisoned mice. However, zinc phosphide is still extremely toxic and will kill sheep, cows, <a href="http://npic.orst.edu/factsheets/archive/znptech.html">pets and even humans</a> if directly eaten. </p>
<p>Rolling out double-strength zinc phosphide may be the lesser of the evils in causing secondary poisoning, but only if used very carefully.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1392315030012522497"}"></div></p>
<p>And another way to help control the mouse plague is to limit food resources for mice on farms. Farmers can minimise <a href="https://groundcover.grdc.com.au/weeds-pests-diseases/pests/harvest-clean-to-keep-mouse-numberslean">grain on ground</a>, and Australia should invest in research for <a href="https://extensionpubs.unl.edu/publication/9000016360405/rodent-proof-construction-structural">grain storage facilities</a> that are less permeable to mice.</p>
<p>Mouse plagues are a regular cycle in Australia. Natural predators not only help create healthy, natural ecosystems, but also they help with mouse control. Second generation rodenticides will only destroy and weaken the predator populations we need to help us combat the next plague.</p><img src="https://counter.theconversation.com/content/160995/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Davis is a member and former director of Birdlife Australia, a member of the Society for Conservation Biology and the Ecological Society of Australia.</span></em></p><p class="fine-print"><em><span>Bill Bateman receives funding from the Holsworth Wildlife Research Endowment. </span></em></p><p class="fine-print"><em><span>Damian Lettoof receives funding from the Holsworth Wildlife Research Endowment; and is a member of the Australian Society of Herpetologists, Ecological Society of Australia and Society of Environmental Toxicology and Chemistry.</span></em></p><p class="fine-print"><em><span>Maggie J. Watson is affiliated with Charles Sturt University and is a member of the board of the Ecological Society of Australia. </span></em></p><p class="fine-print"><em><span>Michael Lohr has previously received funding from funding from the Holsworth Foundation and Birdlife Australia. He is a member of with Birdlife Australia</span></em></p>The NSW government has secured an extremely toxic bait to try to end the mouse plague. But there are safer alternatives.Robert Davis, Senior Lecturer in Wildlife Ecology, Edith Cowan UniversityBill Bateman, Associate professor, Curtin UniversityDamian Lettoof, PhD Candidate, Curtin UniversityMaggie J. Watson, Lecturer in Ornithology, Ecology, Conservation and Parasitology, Charles Sturt UniversityMichael Lohr, Adjunct Lecturer, Edith Cowan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1227962019-09-02T15:15:11Z2019-09-02T15:15:11ZBarn owls reflect moonlight in order to stun their prey<figure><img src="https://images.theconversation.com/files/290516/original/file-20190902-175714-8g3goq.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C7360%2C4891&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/barn-owl-flight-hunting-black-background-1082537198?src=-1-8">FJAH/Shutterstock</a></span></figcaption></figure><p>Ecosystems that are bathed in light during the day change profoundly at night. As the sun fades from the land, nocturnal life emerges, with the barn owl (<em>Tyto alba</em>) among them. Barn owls are iconic nocturnal birds of prey that are found all over the world, often near towns and villages. Although a familiar species to many, there is still much we don’t know about them.</p>
<p>One peculiarity is the difference in plumage colour between different barn owls. Why is it that some have undersides that are completely white while others are dark red? This puzzled scientists for a long time, but finally, we have an answer.</p>
<p>The light conditions in sunlit environments determine how the colour traits of animals evolve, as the composition and quantity of light affects how well an animal is seen by predators or competitors. The stripes of a tiger, for instance, allow this large cat to easily disappear in the dense Indian forest, where the shifting canopy <a href="https://academic.oup.com/beheco/article/28/2/373/2674187">splits light into lines</a>. But how light conditions affect the colouration of nocturnal species is less well understood. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=418&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=418&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=418&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=525&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=525&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290513/original/file-20190902-175710-bn2eha.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=525&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">White-chested and red-chested barn owls both hunt rodents at night – but their success depends on the moonlight.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Kerkuil_licht_en_donker.jpg">Kerkuil/Wikipedia</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span>
</figcaption>
</figure>
<p>The light at night changes according to the lunar cycle. Go out on a night with a new moon in a rural area and you’ll need a torch to see. Do the same on a night with a full moon and you’ll probably have enough light to see without one. How do barn owls deal with these radical changes in light levels from night to night?</p>
<p>We thought they would have a harder time hunting the rodents they need to feed their offspring on moonlit nights. In the bright moonlight, owls should be more easily spotted by prey such as mice. If this was true, hunting on moonlit nights would be even trickier for white owls than for red owls, simply because white is more reflective and therefore more visible in the moonlight than dark red plumage. As it turns out, we couldn’t have been more wrong.</p>
<h2>Blinded by the moonlight</h2>
<p>We’ve been following a Swiss population of barn owls for more than 20 years, monitoring their hunting behaviour with cameras and GPS trackers and recording when they breed each year and how their offspring develop in the nest. By studying this rich data set, we found that barn owls do indeed have a harder time on moonlit nights. They’re less successful hunters and bring less prey to the nest and as they receive less food, their offspring don’t gain as much weight and the youngest have lower chances of surviving and fledging. This was true for red barn owls, but not, surprisingly, for white barn owls. On the contrary, white barn owls seemed to be doing just as well during full moon nights as when there was no moon.</p>
<p>Perplexed, we decided to look at the problem from the perspective of the rodents that barn owls hunt every night. Our experiment investigated how common voles – <a href="https://www.woodlandtrust.org.uk/blog/2019/01/what-do-owls-eat/">the main prey of barn owls</a> – see and react to white and red owls under full and new moon light conditions. </p>
<p><a href="https://www.nature.com/articles/s41559-019-0967-2">We found</a> that prey detected owls more easily on full moon nights, regardless of what colour they were. We knew when the rodents had detected an owl because they froze. Staying immobile is a common prey behaviour, as they aim to stay undetected and allow the risk to pass. Curiously, on full moon nights and only when facing a white owl instead of a red one, rodents stayed frozen for longer.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290489/original/file-20190902-175682-1kshq87.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">Researchers huddle in the dark to study barn owls mid-hunt.</span>
<span class="attribution"><span class="source">Jérémy Bierer</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We think voles behave that way when encountering a white owl because they’re scared by bright light reflected from the white plumage. This fear is well ingrained within rodents – medical researchers expose rodents to bright light to measure their fear response and test drugs on them which are designed to treat anxiety. The white plumage of barn owls exploits this fear by reflecting moonlight. This may explain why white plumage – a very rare trait in nocturnal animals – evolved in this species.</p>
<p>This discovery should remind people how important it is to better understand and preserve nocturnal wildlife and the environments they live in. Minimising light pollution and letting the night be as dark as the moon dictates could benefit beautiful barn owls.</p><img src="https://counter.theconversation.com/content/122796/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Almut Kelber receives funding from Lund University, Sweden, the K & A Wallemberg Foundation, Stockholm and the Swedish Research council.. </span></em></p><p class="fine-print"><em><span>Alexandre Roulin and Luis Martín San José García 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>Scientists have discovered how the wise old barn owl is so good at catching rodents.Almut Kelber, Professor of Biology, Lund UniversityAlexandre Roulin, Professeur, Chercheur Ornitologue, Université de LausanneLuis Martín San José García, Postdoctoral Researcher in Evolutionary Biology, Université de LausanneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/798652017-08-02T15:45:02Z2017-08-02T15:45:02ZWhy controlling rats on small-scale African farms is vital for food security<figure><img src="https://images.theconversation.com/files/180505/original/file-20170801-21062-ppzt0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In many parts of Africa rodents often cause crop losses.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><a href="http://www.pnas.org/content/113/52/14964.short">Recent analysis</a> suggests that Africa will only be able to achieve food security if it invests in crop intensification like increased fertiliser and pesticide input per hectare. But the expansion of agricultural production areas can also improve this. </p>
<p>A complicating factor in African agriculture is that most of the production comes from relatively <a href="http://www.sciencedirect.com/science/article/pii/S0305750X15002703">small farms</a>. Most of these are less than 2 hectares in size. This is much smaller than in Europe and the Middle East where most farms are greater <a href="http://ec.europa.eu/eurostat/statistics-explained/index.php/File:Distribution_of_holdings_and_utilised_agricultural_area_by_size_class_(utilised_agricultural_area),_EU,_2005_and_2010.png">than 10 hectares</a>. In Latin America most farms <a href="http://www.globalagriculture.org/report-topics/industrial-agriculture-and-small-scale-farming.html">exceed 50 hectares</a>.</p>
<p>This means that addressing issues that affect small scale farmers’ productivity can play an important role in food security. Most farmers simply can’t afford pest management control. Often, these methods are lacking in rural areas. And where there are products it can be adulterated or misused. </p>
<p>Agricultural pests are one of the key factors affecting small holder farmer production. In many parts of Africa large population outbreaks of rodents occur often and can sometimes lead up to <a href="http://books.irri.org/9789712202575_content.pdf">100% crop loss</a>. Rodents can damage nearly every crop people try to grow. It’s often difficult to measure chronic damage because it happens over the entire growing season and even after the crop is harvested.</p>
<h2>The neglected rodents</h2>
<p>Efforts to control pests face a number of challenges. Firstly, management is often limited, because of the high cost of herbicides, insecticides and rodenticides. On top of this they aren’t readily available in local farming areas. And most pest control focuses on invertebrate pests like stem borers, armyworm and locusts. Very little attention is paid to vertebrate pests like rodents or birds like the <a href="http://www.irinnews.org/news/2009/08/19">red-billed quelea</a> (<em>Quelea quelea</em>).</p>
<p>Rodents are a particularly important group of pests. Agriculturally, they can inflict considerable economic damage because of their abundance, diversity, feeding habits and high reproduction abilities. </p>
<p>Research on rodent pest control tends to be neglected. But some community based development programmes are looking at how rodents can be controlled using <a href="http://projects.nri.org/ecorat">ecological methods</a>. <a href="https://www.youtube.com/watch?v=nWTC9ZE25EQ">Ecologically-based rodent management</a> involves, firstly, increasing our understanding of their population biology, social behaviour, taxonomy and community ecology. These insights can then be used to develop effective and sustainable management strategies. This approach has been effective in reducing pest damage as well as <a href="http://www.sciencedirect.com/science/article/pii/S1573521404800113">reducing reliance on rodenticide poisons</a> in many countries. </p>
<p>There is little data on the effects of pest control on rodents, particularly when it comes to small holder farming systems. To gain a better understanding we did a <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0174554">systematic review</a> on the effect of rodent pests on small holder farming in Africa and the island nation of Madagascar. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.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">The damage to maize caused by rats.</span>
<span class="attribution"><span class="source">Author supplied</span></span>
</figcaption>
</figure>
<h2>Rodent management in Africa</h2>
<p>Our review highlighted several important findings. We found median crop losses (midpoint of reported losses) attributed to rodent pests were around 15%. This has a significant impact on small holder grain yields and is comparable to losses from cereal stem borers in Africa where much greater investments have been made in <a href="http://onlinelibrary.wiley.com/doi/10.1111/een.12216/full">control programmes</a>.</p>
<p>But there was a big discrepancy in estimated and reported losses, which highlights the importance of standardising research protocols. For example, very little research has been done to try and find a link between rodent density to crop impact. This limits the setting of reasonable management thresholds on when to control rodents based on their density. </p>
<p>Most importantly, we found a paucity of research investigating effectiveness of control measures on rodent pests.</p>
<p>We made several detailed recommendations that we feel will improve the robustness of rodent pest research. The most important ones included the fact that researchers must adopt a “meta-analytic” <a href="https://link.springer.com/chapter/10.1007/978-3-319-55895-0_25">framework</a>. For example, they must place their study in the context of prior literature and they must report on the effect of rodent control, particularly making the comparison between studies and strategies more explicit. This framework has been successfully applied to other evidence based research fields <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049418">like medical research</a>. </p>
<p>Another was that researchers and funding organisations must be encouraged to establish and fund <a href="https://academic.oup.com/bioscience/article-abstract/67/3/271/3057250/Long-Term-Studies-Contribute-Disproportionately-to?redirectedFrom=fulltext">long-term studies</a>. Once a firm foundation has been established on understanding the drivers of population cycles of the dominant rodent pest species, other important aspects like management and community ecology can be successfully developed. </p>
<p>For example, in some African countries – like Tanzania – there have been great improvements in understanding the ecology of pest rodent species. Researchers showed that rainfall plays an important role in predicting rodent pest outbreaks. This facilitated regional planning to control rodent pests in agricultural areas. </p>
<p>We also found that researchers must focus more on empirical treatment control studies that test a management action compared to no management actions. These must be done with suitable replication that investigates management actions on rodent pest populations and associated crop losses. For example, our <a href="http://www.sciencedirect.com/science/article/pii/S1049964416301256">recent meta-analysis showed</a> that avian predators, like barn owls, can reduce rodent pests.</p>
<p>Lastly, we suggest that ecologically based rodent management activities and research should be carried out by multidisciplinary and interdisciplinary teams. In this way research can be sustained over a longer period if there’s collaboration, knowledge is transferred and communities are involved.</p><img src="https://counter.theconversation.com/content/79865/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lourens Swanepoel receives funding from Sasol Agricultural Trust (South Africa), International Foundation for Science (D/4984-2), European Union through its ACP S & T programme (StopRats; FED2013-330223; <a href="http://www.acp-hestr.eu/">http://www.acp-hestr.eu/</a>). He is affiliated with the African Institute for Conservation Ecology and Genetics (AICEG) (Not for profit organization).</span></em></p><p class="fine-print"><em><span>Steven Belmain currently receives funding from the McKnight Foundation, the European Development Fund and the Netherlands Organisation for Scientific Research.</span></em></p>Agricultural pests are one of the key factors affecting small holder farmer production. Focus is normally put on invertebrate pests, but rodents can do severe damage to crops as well.Lourens Swanepoel, Associate lecturer, University of VendaSteven Belmain, Professor of Ecology, University of GreenwichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/593792016-05-20T01:10:20Z2016-05-20T01:10:20ZHidden housemates: rats in the ranks<figure><img src="https://images.theconversation.com/files/123291/original/image-20160520-4451-87u0j1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rats are true natives of our cities. </span> <span class="attribution"><span class="source">Rat image from www.shutterstock.com</span></span></figcaption></figure><p>Rats send shudders down many peoples’ spines, and may in fact be <a href="http://www.theweek.co.uk/72404/david-attenborough-turns-90-six-things-you-didnt-know">Sir David Attenborough’s least favourite animal</a>. But despite their poor reputation, rats are astonishingly successful. </p>
<p>Almost everywhere humans have built their cities, rats have set up their homes – to live with us and off us.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=556&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=556&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123290/original/image-20160520-4478-ziwr7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=556&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Black rats are the most common rats in Australia’s cities.</span>
<span class="attribution"><span class="source">Peter Banks</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Know your rodents</h2>
<p>In Australia we have two species of rat that can be considered truly <a href="https://en.wikipedia.org/wiki/Commensalism">commensal</a> - a species that lives off the resources provided by us. </p>
<p>The black rat (<em>Rattus rattus</em>), or ship rat, is the species of rat that people will most often encounter in their houses in Australia. Then there is the brown rat (<em>Rattus norvegicus</em>), also known as the Norway rat (although it doesn’t come from Norway). This is the species that is often kept as pets and used in lab research. </p>
<p>In the northern hemisphere, the much larger brown rats seem to outcompete black rats. But in Australia and New Zealand, <a href="https://www.researchgate.net/profile/Carolyn_King4/publication/230223984_Invasive_European_rats_in_Britain_and_New_Zealand_Same_species_different_outcomes/links/00b7d53c6e91977d3a000000.pdf">black rats are more widespread</a> and common than brown rats, for reasons we don’t fully understand.</p>
<p>Australia also has 60 species of native rodents, including eight species of native <em>Rattus</em> that evolved from from ancestors which arrived about a million years ago. Similar in size to black rats, these native rats have probably prevented the spread of black rats into natural areas, as has happened in New Zealand and Pacific islands which lack native rodents. </p>
<p>It can be hard to tell a black rat from a native bush rat (<em>Rattus fuscipes</em>), but black rats are more slender with longer tails, and bush rats are chubbier. It is easier to pick a brown rat, which is more than twice the size of a black rat. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=368&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=368&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=368&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=463&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=463&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123280/original/image-20160519-4475-jlip2e.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=463&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Native bush rats are chubbier than their introduced relatives.</span>
<span class="attribution"><span class="source">Peter Banks</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Arrival</h2>
<p>Black rats probably came to Australia <a href="http://publications.rzsnsw.org.au/doi/abs/10.7882/AZ.2011.058">with the First Fleet</a>. There are skeletons of black rats in the gun barrels of sunken Dutch ships off Western Australia, but there is no evidence that their invasion of Australia began before the English landed in Sydney, when they literally jumped ship.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/122807/original/image-20160517-15924-smte5e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&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 first black rat specimens collected in Sydney were mistaken for native rats.</span>
</figcaption>
</figure>
<p>The Macleay Museum at the University of Sydney has the first recorded black rat specimens. These were initially thought to be a native species and given the name <a href="http://www.ecosmagazine.com/paper/EC12344.htm"><em>Hapalotis arboricola</em></a>. In fact, there are loving descriptions of it climbing in local fig trees and <a href="http://www.biodiversitylibrary.org/page/30988090#page/999/mode/1up">entertaining the residents of Mosman</a>. These rats were, however, black rats. They still climb fig trees in Mosman, and are still mistaken for native rodents. </p>
<p>The name black rat is a bit of a misnomer. We have trapped black rats from around Sydney Harbour in many colours, from light fawn, to chestnut brown with white patches, to light grey and sometimes dark grey, and only occasionally black. They can be very cute.</p>
<h2>A very long engagement</h2>
<p>Remains of black rats have been found in Indus civilisations from 4,000 years ago, and even earlier from Israel and the Middle East. They probably originated in India, and are likely to have adapted to human settlement many times in their history. </p>
<p>The black rat is now one of the most widely distributed animals in the world, perhaps only surpassed by humans and house mice. The live on every continent except Antarctica.</p>
<p>What brings them to our houses? The houses we live in provide rats with the secure, thermally stable homes they need to breed in. They eat a vast range of foods, and so can exploit our waste. The urban environments we have created are also relatively free of predators.</p>
<p>When conditions are ideal, black rats can reach very high numbers, giving birth to up to 12 young every five weeks or so. But the urban myths that there is one rat for every person, or that you are never less than six feet from a rat, have <a href="http://www.bbc.com/news/magazine-20716625">little support</a>. In truth, we have no real idea of how many introduced rats there are in Australian cities. </p>
<h2>Unwelcome housemates</h2>
<p>Rats are often unwelcome housemates because of the diseases they spread in their urine and faeces, including leptospirosis (Weil’s disease), salmonella, and <em>E. coli</em>. <a href="https://www.researchgate.net/profile/Dieter_Hochuli/publication/275256855_Are_urban_bandicoots_solely_to_blame_for_tick_concerns/links/558a4cf508ae4e384e261fb1.pdf">They are also hosts of ticks</a> that transmit bacterial infections and induce allergic reactions. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123289/original/image-20160520-4478-44226c.png?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"></a>
<figcaption>
<span class="caption">Black rats are important carriers of disease.</span>
<span class="attribution"><span class="source">Peter Banks</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Black rats are important hosts of the parasites <em>Toxoplasmosis gondii</em> and rat lungworm - both of which can be fatal to native wildlife and humans. Rats are also famous for carrying the plague, which arrived in Australia in the early 1900s but fortunately died out. Australia remains plague-free.</p>
<p>Rat damage infrastructure when building their nests. They chew electrical cables, increasing the risk of house fires, although why they do this is not clear. </p>
<p>But they actually spend less time in our houses than many people think, more often making use of backyards. They seem especially to love aviaries and hen houses, which provides a ready source of spilled food and underground shelter. </p>
<h2>Aliens, or just wild?</h2>
<p>Just as native rats belong in natural environments, <a href="http://www.publish.csiro.au/?paper=WR15048">cities are rats’ natural habitat</a>. They may be introduced in Australia, but they have evolved in the urban habitats we have imported. </p>
<p>However, black rats can spill over from cities to remnant bushland, entering an environment that has <a href="http://www.publish.csiro.au/?paper=WR15048">not adapted to them</a>. Here they have the potential to <a href="http://publications.rzsnsw.org.au/doi/abs/10.7882/AZ.2011.058">wreak all kinds of havoc</a>.</p>
<p>Black rats are adept climbers and raid birds nests to prey on the eggs of small native birds, which may be one reason why these birds are uncommon in city parks. They also prey on other tree-dwelling wildlife such as <a href="http://rsbl.royalsocietypublishing.org/content/9/3/20121144.short">small bats</a>, skinks and spiders. </p>
<p>In contrast, native bush rats are clumsy climbers, and the type of lungworm carried by native rats doesn’t seem to have the same impact on wildlife and people.</p>
<p>Black rats are aided in this conquest by humans. Almost <a href="http://www.publish.csiro.au/?paper=WR15048">70% of rats living in bushland next to houses have visited those houses sometime in the previous two weeks</a>. This undoubtedly helps to increase rat populations beyond what the natural environmental alone could support. In contrast, native rats rarely visit houses.</p>
<p>So even though black rats are native to our cities, they can still be pests to humans and other wildlife. Killing rats with poison or traps is one option, but the best strategy is to reduce their access to food and shelter. Make sure your neighbours are doing the same, and aren’t providing a refuge for the rats jumping ship from your home. </p>
<p><em>This article is part of a <a href="https://theconversation.com/au/topics/hidden-housemates">series profiling our “hidden housemates”</a>. Are you a researcher with an idea for a “hidden housemates” story? <a href="mailto:james.whitmore@theconversation.edu.au">Get in touch</a>.</em></p><img src="https://counter.theconversation.com/content/59379/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Banks receives funding from The Australian Research Council, NSW Office of Environment and Heritage, Taronga Conservation Society Australia, Mosman Council, Rentokil, Bayer, National Parks and Wildlife Service, NZ Ministry of Business, Transport for NSW, The Paddy Pallin Foundation, Manly Council, and The Australian Wildlife Conservancy</span></em></p>Rats have lived with us for thousands of years.Peter Banks, Professor of Conservation Biology, School of Life and Environmental Sciences, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/296772014-07-24T14:28:42Z2014-07-24T14:28:42ZThe marmot, a hungry dog and how to put down plague in modern China<figure><img src="https://images.theconversation.com/files/54815/original/d869m6ft-1406211907.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The accused: a marmot.</span> <span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/Gray_marmot#mediaviewer/File:Marmota_baibacina.jpg">Alastair Rae</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Chinese authorities have lifted a nine-day quarantine on a town in the country’s northwest that saw a <a href="http://www.medicalnewstoday.com/articles/280072.php">resident die of the plague</a>. The victim is thought to have caught the disease from a dead marmot, which he fed to his dog. Shocking though this might sound, plague did not die out with the Black Death of the Middle Ages for which it is most famous.</p>
<p>Plague, caused by a bacteria called <em>Yersinia pestis</em> is primarily a pathogen of rodents, in particular rats. It spreads between animals through biting fleas (which the rats carry). When the host rat dies from the plague, the fleas then seek out a new host. Occasionally the bacteria can be <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1948-7134.2009.00004.x/abstract">transmitted to other animals – including marmots</a> – as well as to humans. The wiping out of large numbers of rodents has often preceded outbreaks of human infection.</p>
<p>Plague has shaped human civilisation through three major global outbreaks. It is estimated that the notorious 14th century pandemic, known as the Black Death (1347-1351) killed over half of the world’s population, 30–50% of the European population, and reduced England’s population by 1.4 million, leaving approximately 2.8 million survivors in only a five-year period. Plague was present in Europe and around the Mediterranean every year between 1346 and 1671. An outbreak between 1479–80 killed up to 1 in 5 people in England and outbreaks occurred periodically until the Great Fire of London in 1666.</p>
<h2>Symptoms: bubonic and pneumonic</h2>
<p>Plague symptoms depend on how the bacteria has been transmitted. A flea bite gives rise to the “Bubonic” form, with the swollen black “bubos” or enlarged lymph nodes near the bite site. Gangrene of the fingers, toes, lips and nose is another common symptom. Symptoms appear suddenly, usually two to five days after exposure to the bacteria and can include vomiting of blood and extreme pain, caused by decay of the skin while the patient is still alive.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/54813/original/8g7ys5j5-1406211493.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">Adverse effects of the bubonic plague.</span>
<span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/Bubonic_plague#mediaviewer/File:Smallpox01.jpg">Fingalo</a></span>
</figcaption>
</figure>
<p>Pneumonic plague develops when the bacteria reaches the lungs. It is contagious – so if someone has pneumonic plague and coughs or sneezes, droplets containing plague bacteria can be inhaled by others nearby. Initially symptoms are fairly general with headaches, weakness and coughing, but death rapidly follows in as little as 24 hours. </p>
<p>The pneumonic form of the disease is always fatal if left untreated. This foregone conclusion of rapidly succumbing to the bacteria after catching it has resulted in <em>Y. pestis</em> being categorised as an agent of biowarfare.</p>
<h2>The plague today</h2>
<p>Many people think of plague as a disease of the past. In fact, plague is still endemic in several areas around the globe today, including the western United States, South-East Asia and southern Africa. Every few months there are <a href="http://www.promedmail.org/">suspected new cases or outbreaks in humans</a>. Between 1964 and 2003, over 80,000 human cases and 6,500 deaths have been documented by the World Health Organisation. </p>
<p>But human infection is rare and treatment is available. Speedy treatment is vital – as infection can kill very quickly – with antibiotics, such as Streptomycin and Chloramphenicol, able to do the job of curing patients.</p>
<p>The Chinese authorities’ decision to quarantine 151 people in the local hospital was therefore appropriate. All had come into close contact with the infected man so it was important to monitor them for symptoms and ensure quick treatment. The incubation time for pneumonic plague is anything from two hours up to four days, with death in one to six days, so this fits in with the time this village was quarantined.</p>
<p>Recently, however, multiple drug resistant strains of plague <a href="http://aac.asm.org/content/50/10/3233.full">have been reported</a>. Misdiagnosis and lack of treatment still lead to deaths. In addition, a vaccine is available but it is only generally given to people working in affected areas that are likely to be exposed – and <a href="http://www.ncbi.nlm.nih.gov/pubmed/10796565">its efficacy has been questioned</a>.</p>
<p>The recent case in China shows how incidences of the plague can be handled today to prevent something anywhere near as severe as the Black Death from happening again. With early identification it can be treated and areas put into quarantine to prevent it from spreading. But the growth of drug-resistant strains adds further ammunition to the need for better surveillance to develop new antibiotics. </p><img src="https://counter.theconversation.com/content/29677/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Stabler receives funding from Wellcome Trust and European Union.</span></em></p>Chinese authorities have lifted a nine-day quarantine on a town in the country’s northwest that saw a resident die of the plague. The victim is thought to have caught the disease from a dead marmot, which…Richard Stabler, Senior Lecturer in Molecular Bacteriology, London School of Hygiene & Tropical MedicineLicensed as Creative Commons – attribution, no derivatives.