tag:theconversation.com,2011:/id/topics/tadpoles-4746/articlesTadpoles – The Conversation2022-07-24T12:28:50Ztag:theconversation.com,2011:article/1865352022-07-24T12:28:50Z2022-07-24T12:28:50ZFinding their song: Reviving the declining western chorus frog population is now critical<figure><img src="https://images.theconversation.com/files/474439/original/file-20220717-12-38fv83.jpg?ixlib=rb-1.1.0&rect=19%2C96%2C4262%2C2747&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The population of western chorus frogs has been declining over the past 60 years and continues to be an issue across Canada.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>In November 2021, Canadian Minister of Environment and Climate Change Steven Guilbeault declared <a href="https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/orders/western-chorus-frog-longueuil-emergency-protection-order-summary.html">an emergency order that put an immediate halt</a> on a residential development in Longueuil, Que., to protect the critical habitat of one of Canada’s threatened amphibian species — the western chorus frog. </p>
<p>While this was one of the few cases where the federal government applied the Species at Risk Act to cease development on private land, the Canadian Shield’s population of western chorus frog — in addition to many other <a href="https://doi.org/10.1186/s12983-021-00425-w">closely related species</a> — has declined over the past 60 years and <a href="https://longpointbiosphere.com/download/Herptiles/Perspectives-on-amphibiam-population-declines-Green-1997.pdf">continues to be an issue in Canada</a>. </p>
<p>It was recently announced that the proposed route of Highway 413 in Ontario will impact the habitat of <a href="https://thenarwhal.ca/highway-413-endangered-species/?fbclid=IwAR0sh374OVqgaqor0eLVB8fX-VQT3omUYnUp8FccKe8CcMgQiJ4_QFkMhPI">11 species at risk</a>, including the western chorus frog. The recent disappearance of this frog and its habitat — specially in portions of Ontario and Québec — has caused substantial <a href="https://www.cbc.ca/news/canada/montreal/game-changer-court-ruling-gives-federal-government-right-to-protect-western-chorus-frog-1.4741646">concern and controversy</a>.</p>
<p>As a behavioural ecologist specializing in acoustics and a reproductive endocrinologist who invented an <a href="https://doi.org/10.1016/j.ygcen.2016.03.024">injectable hormone mixture</a> that induces frog breeding, we believe hope still exists. Habitat protection and restoration, advanced reproductive technologies and reintroduction procedures are all at our fingertips. This multifaceted approach could help slow further declines of chorus frogs and other amphibians. </p>
<h2>Global and local threats</h2>
<p>Despite its small size — measuring only two to three centimetres in length and often weighing less than two grams — the western chorus frog produces a loud, clear trill that is reminiscent of running a thumb across a plastic comb. </p>
<p>Historically, it was one of the most abundant amphibians in eastern Ontario and Québec. Now, it is found in <a href="https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/recovery-strategies/western-chorus-frog-canadian-shield-population.html">only 10 per cent of their original range</a>.</p>
<figure class="align-right ">
<img alt="A dark brown frog with light brown markings" src="https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=486&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=486&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=486&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=611&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=611&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473222/original/file-20220708-27-8qc00h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=611&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An adult female western chorus frog (Pseudacris triseriata).</span>
<span class="attribution"><span class="source">(Chris Callaghan)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Amphibians, including the western chorus frog and other frogs, toads and salamanders, play critical ecological roles in the environment. They are vital pieces in the local food chain. They are also economically important, as they provide free pest control in residential areas by consuming insect species, such as mosquitoes and blackflies, without the need of <a href="https://theconversation.com/are-mosquito-killing-natural-pesticides-unintentionally-harming-frogs-175194">pesticides that are potentially harmful to wildlife</a>. </p>
<p>Across the world, these amphibian species are rapidly disappearing due to habitat loss, disease, pollution, harvesting, invasive species and <a href="https://doi.org/10.1038/35070552">climate change</a>. Over 40 per cent of species are <a href="https://journals.openedition.org/sapiens/1406">threatened with extinction</a>. Amphibian declines are part of the <a href="https://doi.org/10.1073/pnas.0801921105">sixth mass extinction</a> event on Earth, on a scale that is approaching the loss of dinosaurs. </p>
<h2>Captive breeding can aid reintroduction of frogs</h2>
<p>One strategy for conserving declining species is to collect individuals from the wild and breed them in <a href="https://doi.org/10.1111/cobi.12612">laboratory or captive settings</a>.</p>
<p>This allows the offspring to grow without being threatened by predators, contaminants or other disturbances. The healthy offspring can then be released to boost numbers in the natural environment. </p>
<p>Along with Marc Mazerolle’s team at Laval University, we implemented this strategy through a recent collaborative effort with the Montreal Biodome and Sépaq (Société des établissements de plein air du Québec), with the goal of increasing the number of healthy individuals that can be released into appropriate restored natural sites to the benefit of all.</p>
<p>Two years into the project, adult chorus frogs have been successfully bred in captivity. Hundreds of tadpoles have been reared to froglets and released in constructed wetlands for the species. Some of the introduced individuals survived their first winter and adult males could be heard calling for females this past spring. These methods can be applied to species around the world.</p>
<h2>The critical role of awareness and conservation</h2>
<p>The first step is to spread awareness to emphasize the importance of amphibians and the speed at which species are declining. There are several resources and citizen science projects dedicate to the protection of amphibians, such as <a href="http://amphibian-reptile-conservation.org/index.html">Partners in Amphibian and Reptile Conservation</a> and <a href="https://www.amphibians.org/">Amphibian Survival Alliance</a>.</p>
<p>Protection of wetlands from destruction and pollution is one of the best ways to help. Wetlands are critical to the survival of amphibians. During the construction of housing developments and infrastructure — such as the proposed Highway 413 — wetlands are often <a href="https://trid.trb.org/view/148062">drained or filled in</a>. Wetlands host many beautiful bird and plant species, not only amphibians, and they act as the earth’s filter to <a href="https://doi.org/10.1016/j.tree.2005.11.015">increase water quality</a>.</p>
<figure class="align-center ">
<img alt="A wetland" src="https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473266/original/file-20220710-7520-dxircz.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">
<figcaption>
<span class="caption">Wetlands act as typical habitats for western chorus frogs and other amphibians.</span>
<span class="attribution"><span class="source">(Jeffrey P. Ethier)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Being careful while walking or driving near wetlands is another way to help on an individual level. Avoid disturbing breeding amphibians. Leave the tadpoles in the water. Observe and enjoy watching them grow legs and climb out of the water for the first time! Protecting the local ponds near your home can also contribute to this conservation.</p>
<p>You can also participate in public forums and let your community know that you support sustainable and responsible land use that keeps wetland habitats connected and protects critical areas for threatened species. Form volunteer groups to help protect frogs as they migrate over roads in the spring breeding season, <a href="https://www.researchgate.net/publication/233740122_40_years_of_Natterjack_toad_Conservation_in_Europe">as seen in other countries</a>. We all have the power to make a positive difference in the protection of amphibians.</p><img src="https://counter.theconversation.com/content/186535/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jeffrey Ethier receives funding from the Natural Sciences and Engineering Research Council of Canada (NSERC). </span></em></p><p class="fine-print"><em><span>Vance L Trudeau receives funding from Environment and Climate Change Canada and Ministère des Forêts, de la Faune et des Parcs.</span></em></p>Habitat protection and restoration, advanced reproductive technologies and reintroduction procedures could help slow the decline of western chorus frogs and other amphibians.Jeffrey P. Ethier, PhD candidate, Department of Biology, L’Université d’Ottawa/University of OttawaVance L Trudeau, Professor, Department of Biology, L’Université d’Ottawa/University of OttawaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1545612021-03-28T19:03:20Z2021-03-28T19:03:20ZThe secret life of puddles: their value to nature is subtle, but hugely important<figure><img src="https://images.theconversation.com/files/389715/original/file-20210315-21-1k3b3ms.jpg?ixlib=rb-1.1.0&rect=7%2C14%2C2446%2C1777&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>It’s official: Australians endured the <a href="https://phys.org/news/2021-03-wettest-summer-yearsbut-la-nina.html">coldest, wettest summer</a> in at least five years thanks to La Niña, a <a href="https://theconversation.com/la-nina-will-give-us-a-wet-summer-thats-great-weather-for-mozzies-147180">climate phenomenon</a> over the Pacific Ocean. </p>
<p>Before we knew it, autumn rolled in bringing more rain. Tragically, it led to widespread flooding across New South Wales, but elsewhere it helped to create more puddles. In our urban environments puddles are inconvenient: they can damage property and block our paths. But from a biological perspective, puddles are very important components of microhabitats and biodiversity. </p>
<p>We know for many animals — including birds and pets — puddles are a ready source of drinking water and provide a much-needed bath after a hot and dusty day. They’re also well known for providing water-reliant species such as mosquitoes with opportunities for breeding, and many of us may remember watching tadpoles developing in puddles as children. </p>
<p>But puddles make more nuanced and subtle contributions to the natural world than you may have realised. So with more rain soon to arrive, let’s explore why they’re so valuable. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Rainy day on Swanston St, Melbourne" src="https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389710/original/file-20210315-23-3q7e9k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Puddles are getting harder to find in urban environments.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Take a closer look</h2>
<p>Puddles are a diverse lot. They can be small or large, shallow or deep, long lasting or gone in a matter of hours. If you look closely at a puddle you will often find it is not even, especially on a slope.</p>
<p>Puddles consist of small, naturally formed ridges (berms) and depressions (swales). The berms form from silt and organic matter like leaf litter, which act as mini dams holding back the water in the swales behind them. </p>
<p>Berms and swales can be hard to see, but if you look closely they’re everywhere and contribute to the retention of water, affecting the depth, spread and the <a href="http://www.harvesth2o.com/swales.shtml">very existence</a> of the puddle. </p>
<p>All of this means they meet the needs of different species. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Flooded country path" src="https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389712/original/file-20210315-23-y8cbhs.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">The tiny ridges and depressions in puddles can make a big difference to wildlife.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>On rainy days you may have seen birds such as magpies feeding on worms that wriggle to the surface. Worm burrows can be two to three metres deep and many species might come to the surface to <a href="https://openlearning.une.edu.au/LivingSoils/index.php?u=module01/earthworm.htm#:%7E:text=Some%20worms%20live%20in%20the,to%20feed%20on%20leaf%20litter.">feed on leaf litter</a>. </p>
<p>Worms emerge during and after heavy rain when water floods their burrows and soil becomes saturated. The worms won’t drown but they do need oxygen, which is low in very wet soils. </p>
<p>Often in drier weather, getting a worm is not as easy as you might think — not even for the legendary early bird. So when heavy rain drives worms to the surface, it’s party time for birds that feed on them, and they make the most of the opportunity.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A spotted pardalote near a puddle" src="https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389718/original/file-20210315-17-1dw5k89.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&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 spotted pardalote inspecting puddle.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Swales in puddles often persist for days, which allows water-dependent insects to breed. Mosquito larvae, for instance, <a href="https://www.mosquito.org/page/biology">live in water</a> for between four and 14 days, depending on temperature (so if you’re worried about mozzies, then remember puddles have to persist for days before the pesky pests emerge). </p>
<p>Tadpoles take between <a href="https://sciencing.com/tadpoles-5095167.html">four and 12 weeks</a> to develop into frogs, and requires a deeper, long-lasting puddle. But these puddles are becoming rarer in urban areas, and so it’s not often you see tadpoles or frogs in our suburbs.</p>
<h2>Why seeds love them</h2>
<p>Puddles also provide small, but important, reservoirs where seeds of many plant species germinate. In some cases, the seeds have chemical inhibitors in them, which prevent the seeds from germinating until after a period of heavy rainfall. </p>
<p>Then, the inhibitors are leeched from or diluted within the seeds, allowing them to germinate. Many desert species have this adaptation, including Australian eremophilas (emu bush). </p>
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Read more:
<a href="https://theconversation.com/la-nina-will-give-us-a-wet-summer-thats-great-weather-for-mozzies-147180">La Niña will give us a wet summer. That's great weather for mozzies</a>
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<p>In other cases, plants that grow all year round (annoyingly, weeds among them) need the dose of water puddles provide to kick start their very rapid growth and reproduction. </p>
<p>Easily germinated plants (such as tomatoes and cabbages) and ornamental flowering plants (such as hollyhocks and delphiniums) often require just a little extra water to trigger the whole germination process.</p>
<h2>Important growing opportunities for iconic trees</h2>
<p>Puddles also provide more subtle opportunities for wildlife. Take Australia’s iconic river red gums (<em>Eucalyptus camaldulensis</em>) as an example. River red gums are water-loving trees that can withstand up to nine months of inundation without getting stressed. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="River red gum" src="https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389717/original/file-20210315-17-jzkfry.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">Puddles can wash away plant-inhibiting chemicals from the soil.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>What’s not so well known, however, is river red gums produce chemicals that rain washes from their leaves, accumulating beneath the tree. These chemicals can inhibit the growth of plants, such as weeds, under the canopies. </p>
<p>This effect — where chemicals produced by one plant have an effect on other plants — is called “<a href="https://theconversation.com/the-river-red-gum-is-an-icon-of-the-driest-continent-118839">allelopathy</a>”. Many wattle species <a href="https://www.permaculturenews.org/2016/01/21/plant-allelopathy/">produce allelopathic</a> chemicals and so do some important food plants, such as walnuts, rice and the common pea. </p>
<p>River red gum allelopathic chemicals can prevent the trees’ own seedlings from growing near them. So river red gums require floods to wash the chemicals from the soil away. This mechanism allows river red gums to germinate and regenerate when the soil is wet, and in places away from the competition of mature trees. </p>
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<a href="https://theconversation.com/the-river-red-gum-is-an-icon-of-the-driest-continent-118839">The river red gum is an icon of the driest continent</a>
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<p>Puddles can do the same thing, on a small scale, ensuring trees have plenty of opportunities to persist in the wild. This pattern of regeneration <a href="https://www.permaculturenews.org/2016/01/21/plant-allelopathy">is important</a> to provide a mosaic of species and trees of different ages, making up a diverse range of habitats for other wildlife. </p>
<h2>Puddles are no piddling problem</h2>
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<a href="https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A muddy golden retriever playing in a puddle" src="https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389716/original/file-20210315-13-ytoli1.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>
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<span class="caption">Puddles are becoming harder to find in the suburbs.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>As property developers iron the creases from our created landscapes with much less open space and more paved surfaces, puddles are becoming harder to find close to home. </p>
<p>Taking away puddles removes a whole range of microhabitats, jeopardising the chances of a diverse range of species to breed and persist, especially in urban areas. These days, any loss of biodiversity is worrying. </p>
<p>So when you’re next out and about after or during heavy rain, keep an eye out for puddles.</p>
<p>Remember the life that depends on them and, if you can, try not to disturb them. Perhaps capture the joy of jumping over — rather than in — them. They are not just a nuisance, but a key to a nuanced and biodiverse local community.</p><img src="https://counter.theconversation.com/content/154561/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gregory Moore 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>This autumn, embrace puddles. Even tiny pools of water can be essential for birds, trees and pets — from washing away chemicals on leaves to forcing worms to emerge.Gregory Moore, Doctor of Botany, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1509992021-01-06T14:54:56Z2021-01-06T14:54:56ZHow tadpoles advance the African clawed frog invasion<figure><img src="https://images.theconversation.com/files/373074/original/file-20201204-19-ytu42u.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">African clawed frog tadpoles in the laboratory. </span> <span class="attribution"><span class="source">Natasha Kruger</span></span></figcaption></figure><p>The African clawed frog, a species native to southern Africa, is <a href="https://theconversation.com/invasive-tadpoles-can-recognise-potential-predators-in-new-environments-119673">one of the most successful invaders in the world</a>. Part of the reason is that it has been of particular interest to scientists for a long time.</p>
<p>This frog has had a long history in science since its original description in 1802. It is an atypical frog, with claws on its toes, and spends most of its time in water – unlike other frogs. This fascinated many researchers. They also realised these frogs are easy to maintain in captivity, and even breed under these conditions. So they were useful for dissection in science education and a model organism in physiology research. </p>
<p><a href="https://pubmed.ncbi.nlm.nih.gov/26471494/">Lancelot Hogben</a>, a British biologist who visited Cape Town in 1927, found that this frog was extensively used in South African physiology departments. He discovered that female African clawed frogs can be used as a pregnancy test by injecting a woman’s urine into the frog. The gonadotrophin hormones in the urine of a pregnant woman would induce ovulation in the female frog, which would then lay eggs – a positive pregnancy test. This test was widely accepted and used globally <a href="https://www.bmj.com/content/2/4067/1253">less than 100 years ago</a>. </p>
<p>Thousands of live frogs were exported around the world to use in laboratories, as dissection animals and for pregnancy testing. More recently they have been widely exported as pets too. </p>
<p>Unfortunately, this frog did not stay in captivity. It has been deliberately and accidentally released into the wild in places where it’s not a native species.</p>
<p>Wild populations of the African clawed frog have been discovered in the US, the UK, Europe and southern America. Not only have these populations been established, they have overcome dispersal barriers in their new environments and started to invade. </p>
<p>These frogs can move overland between ponds and rivers for several kilometres. Adults can eat a range of prey items. They compete with native amphibians and prey on them. They are also very adaptable in the new environment. For example, invasive tadpoles of the African clawed frog can recognise and respond to novel predators. This adaptability and competitive ability seems to be contributing to their invasion success. </p>
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<a href="https://theconversation.com/invasive-tadpoles-can-recognise-potential-predators-in-new-environments-119673">Invasive tadpoles can recognise potential predators in new environments</a>
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<p>Understanding the traits which appear to favour or limit the species’ invasion potential can guide measures to control and eradicate it. One aspect that biologists don’t know much about yet is the impact of tadpoles on the invasion potential.</p>
<p>We therefore set out to address this gap in our knowledge. We <a href="https://doi.org/10.1093/biolinnean/blaa191">studied</a> a population in western France and made an unexpected finding. Rapid adaptations in adult frogs were not reducing the survival success of tadpoles. This suggests that not just adult frogs but tadpoles should be targets for control as they can influence the invasion potential of this population. </p>
<h2>The invasive population in western France</h2>
<p>The introduction history of this population in the Deux-Sèvres department is <a href="https://doi.org/10.1163/157075606775904722">well studied</a>. African clawed frogs were released from a breeding facility near the town of Saumur when it closed down in the 1980s. The population has since then spread to cover an area of about 4,500km². </p>
<p>Previous <a href="https://doi.org/10.1111/jzo.12548">studies</a> have <a href="https://doi.org/10.1093/biolinnean/blx048">found</a> that the adults at the introduction point differ from adults found at the expanding population edge. Adults at the periphery were found to have longer hind limbs in relation to their bodies. This may improve their swimming performance and endurance. And the relative mass of their reproductive organs is smaller. These differences – which have evolved in just 40 years – suggest that they are allocating fewer resources to reproduction and more to dispersal. </p>
<p>But little is known about how adaptations in adults affect other life stages such as tadpoles and whether other life stages may limit their dispersal capacity at the edge.</p>
<p>In some frog species, tadpole and adult traits can be coupled. Carryover effects from the development of tadpoles can influence adult size and reproduction, for instance. Trade-offs in resources in adults can affect egg size, clutch size and ultimately tadpole development. The hypothesis was therefore that the African clawed tadpoles in France might be influenced by adaptations in adults and that the tadpole populations at the periphery might be more vulnerable than those at the core.</p>
<p>We studied this by comparing traits of tadpoles from the core and the periphery of the population. These traits included the body size of the tadpoles, the time they took to reach metamorphosis and their survival rate. For instance, it’s <a href="https://doi.org/10.1073/pnas.0603562103">known</a> that a shorter tadpole period usually decreases <a href="https://doi.org/10.3354/cr00878">hind limb length</a>. So we expected to find that tadpoles at the periphery would have a longer tadpole period than those at the core. That longer period might expose the tadpoles to unfamiliar threats at the population periphery. Identifying vulnerable points in the species’ life cycle might provide an opportunity for control and eradication.</p>
<p>But what we found was not what we’d predicted. Tadpoles at the core did not differ from tadpoles at the periphery in terms of size, time to metamorphosis and survival. This indicates that adaptations in adults do not affect tadpole stages. The traits are not coupled. </p>
<p>The changes in adults that allow them to disperse better don’t seem to have a negative effect on tadpoles at the periphery. The tadpoles can function and survive as normal, while adults are changing to increase their dispersal rate. Also, tadpole development does not seem to constrain adult traits. This may ultimately increase the invasion potential of these frogs in this area. </p>
<p>The rapid adaptation in adults at the periphery and the decoupling of traits between life stages presents a challenge to the control of this invader in France. Current strategies mainly focus on the removal of adults. Our study highlights that other life stages such as tadpoles should be targets for control or eradication too as they can affect the invasion potential of this population.</p><img src="https://counter.theconversation.com/content/150999/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Natasha Kruger receives funding from the DSI-NRF Centre of excellence for Invasion Biology, Ambassade de France en Afrique du Sud (France). This study was part of the project Life Control stRategies Of Alien invasive Amphibians (CROAA)—LIFE15
NAT/FR/000864 funded by the Life program of the European Commission. . She is affiliated with Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa and Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France.</span></em></p>Tadpoles at the edge of the population are no more vulnerable than those at the centre.Natasha Kruger, Postdoctoral fellow, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1196732019-09-17T11:35:33Z2019-09-17T11:35:33ZInvasive tadpoles can recognise potential predators in new environments<figure><img src="https://images.theconversation.com/files/284064/original/file-20190715-173325-ildce1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The African clawed frog.</span> <span class="attribution"><span class="source">Author supplied</span></span></figcaption></figure><p><a href="https://www.nationalgeographic.com/environment/habitats/invasive-species/">Invasive species</a> have become an increasingly big threat to indigenous ones as the spread of alien animals and plants has accelerated with the growth of global trade. Some can be very destructive, while some live in close proximity without posing any sort of threat.</p>
<p>Understanding the behaviour of invasive species can provide clues on how to manage them, particularly in situations in which they threaten to wipe out indigenous species.</p>
<p>In <a href="https://www.reabic.net/aquaticinvasions/2019/AI_2019_Kruger_etal.pdf">my research</a> we set out to shed light on how invasive species co-evolve – or don’t – with predators in their new environment. This is an interesting question because invasive species don’t have the advantage of having developed anti-predator mechanisms in their native environment over thousands of years. </p>
<p>To survive, invasive species must be able to identify potential predators. </p>
<p>Species that live in water have developed particular survival mechanisms. For example, smell really matters because predators release signature odours. This means that it’s essential for aquatic prey to detect predators so that they take evasive action. Several defences are possible, such as hiding or avoiding particular areas or reducing their activity.</p>
<p>In our study, we looked at the <a href="https://nationalzoo.si.edu/animals/african-clawed-frog">African clawed frog</a>, <em>Xenopus laevis</em>. Though it is indigenous to South Africa it has become a globally invasive amphibian, successfully establishing populations on four continents: Asia, Europe, North and South America. In western France, African clawed frogs have dispersed over five departments (a word used to describe a certain level of government in the country) since the 1980s. </p>
<p>We tested whether the African clawed frog tadpoles in France had developed ways to protect themselves against local predators. We measured their reactions to three species: an invasive crayfish species, a native diving beetle species, and a non-predator snail as a control. </p>
<p>We found that the tadpoles did indeed take action to avoid detection. Our results show that invasive tadpoles express anti-predator behaviour to both unknown and known predators to reduce predation rates in novel environments. This, in turn, means that they are more likely to survive in new environments.</p>
<h2>Evolutionary histories</h2>
<p>Tadpoles reduced their activity in the presence of both predators, but not in the snail’s presence. Reducing activity is common in tadpoles. Staying still allows them to reduce the probability of being detected.</p>
<p>What was particularly interesting about the tadpoles’ responses was that they were similar even through they had very different evolutionary histories with the three species we chose.</p>
<p>The African clawed frog shares a long evolutionary history with diving beetles in South Africa. On the other hand, the African clawed frog has only recently been exposed to crayfish in France – in other words, over a much shorter evolutionary period. The invasive crayfish is native to north-eastern Mexico and south-central US and was only introduced into France in 1988. This means that the first contact between African clawed frog and crayfish in western France dates back to less than 30 years. </p>
<p>We expected the tadpoles to be more naive to crayfish than the diving beetles due to this short coexistence period. But, this wasn’t the case. We found that they took evasive action when in the vicinity of both the beetle and the crayfish. This involved reducing their activity when either predator was added to the water.</p>
<p>When snails – a non-predator – were added to the water there was no evasive behaviour on the part of the tadpoles. </p>
<p>The results were unexpected because of the lack of co-evolutionary history between the African clawed frog and crayfish. Yet, tadpoles seem to recognise the crayfish as a threat.</p>
<h2>An explanation</h2>
<p>We suggest three different possible hypotheses for this phenomenon. </p>
<p>Firstly, African clawed frogs evolved an anti-predator response to crayfish during their recent contact in western France. Secondly, the odours that crayfish excrete are similar to odours released by freshwater crabs, which are predators in southern Africa. Thirdly, tadpoles exhibit an innate response to any predator odours. </p>
<p>We can’t currently select one hypothesis. But our results raise questions about how invasive populations express anti-predator behaviour to unknown predators, and reduce predation rate in novel environments. </p>
<p>This trait possibly explains the success of the African clawed frog.</p>
<p>Regardless of the mechanism behind the response, our results suggest that this behaviour may limit the ability of crayfish and beetles to control African clawed frog tadpoles in France.</p><img src="https://counter.theconversation.com/content/119673/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Natasha Kruger is a student at the Centre for Invasion Biology, Stellenbosch University and Université Claude Bernard Lyon 1. She receives funding from Centre of excellence for Invasion Biology and Ambassade de France Afrique du Sud. </span></em></p>What was particularly interesting about the responses of the tadpoles was that they were similar even through they had very different evolutionary histories with the three species we chose.Natasha Kruger, PhD candidate Centre of excellence for Invasion Biology, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1148452019-04-11T12:02:11Z2019-04-11T12:02:11ZKiller tadpoles threaten Andaman archipelago’s native frog species<figure><img src="https://images.theconversation.com/files/268549/original/file-20190410-2912-1f6gyis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Carnivorous bullfrog tadpoles don't even spare their own.</span> <span class="attribution"><span class="source">Author supplied</span></span></figcaption></figure><p>The <a href="https://www.iucnredlist.org/species/58301/11760496">Indian bullfrog</a>, which is native to the Indian sub-continent, has recently invaded the Andaman archipelago. This group of islands lies about 1200 km east of the Indian mainland. The bullfrog was probably introduced to the archipelago in the early 2000s – either as adults released for human consumption, as tadpoles that contaminated aqua-cultural stocks, or both.</p>
<p>In these tropical islands of the Bay of Bengal, this large frog – it can grow up to 160 mm in length, a good three to five times larger than the native frogs – has spread remarkably fast. This is cause for concern, both <a href="https://www.thehindu.com/news/national/the-andamans-new-colonisers/article24659652.ece">ecologically and economically</a>. That’s because of the frog’s “anything goes” attitude to feeding. The adults prey on a host of endemic vertebrates, including fishes, frogs, lizards, snakes, and even birds. The bullfrog doesn’t even spare poultry, which many households on the islands keep, making their invasion a problem for the economy too.</p>
<p>Our <a href="https://link.springer.com/epdf/10.1007/s10530-019-01985-z?author_access_token=sN7C1lWmxlJQNNrf6i2UTPe4RwlQNchNByi7wbcMAY7Bqt0RuzImb80Y1kcUW-vC0Js1cdH8sssdTlBLu2Yh2XxpLX_OYYHjZ1a2dhmzj92bcvXNjeoqD114L0CQk8GREhr2_K0YmsYlzH1SeLJhMw%3D%3D">new study</a> reveals that not only the adult bullfrogs pose a threat to the Andaman archipelago’s native frog species: their tadpoles do, too.</p>
<p>We conducted an experiment, simulating real-life conditions, which revealed that no individuals from two native frog species survived the feeding onslaught of the Indian bullfrog’s tadpoles. That’s a level of predation which has never been documented before for the tadpoles of any invasive frog.</p>
<p>If native tadpoles are such easy prey for this carnivorous bullfrog’s tadpoles, their populations could face serious decline. They may even be entirely wiped out on the Andamans. New frog species are often discovered on these islands, and the bullfrog’s tadpoles could also put these at risk.</p>
<h2>The experiment</h2>
<p>The Andaman tree frog and the Chakrapani’s narrow-mouthed frog are found only on the Andaman archipelago. There are many other plant and animals species that are endemic to the Andamans; this uniqueness in diversity has conferred the “biodiversity hotspot” tag on the archipelago. </p>
<p>The Indian bullfrog is a recent entrant to these isolated islands. It breeds in the same paddy field pools and plantations as the narrow-mouthed frog and the tree frog. As all three species breed at the onset of the south-west monsoon in May, their tadpoles begin the process of development together.</p>
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<a href="https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268547/original/file-20190410-2914-w07lwp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Bullfrogs in action: mating on the night of first heavy rains.</span>
<span class="attribution"><span class="source">Author supplied</span></span>
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<p>We wanted to understand how native tadpoles responded to carnivorous bullfrog tadpoles. Would the native tadpoles be able to outmanoeuvre these tadpole predators? Would bullfrogs out-compete native tadpoles for food and slow down their growth and reduce survival? </p>
<p>To answer these questions, we replicated the tadpoles’ breeding grounds by setting up paddling pools – the sort that are appropriate for humans aged between three and ten. Combining the three frogs in all possible permutations, we tasked ourselves with monitoring a total of 25 pools. We were interested in how the tadpoles fared in terms of survival and growth. Tadpole density and the food that’s available are known to affect these parameters, so we kept these equal for all treatments. </p>
<p>Each pool had a total of 30 tadpoles, with equal representation of species in the treatments with more than one species. We replenished each pool with 40g of submerged leaf litter and changed the water (containing zooplanktons) every week.</p>
<h2>Predator and prey</h2>
<p>The stage was set.</p>
<p>As soon as the experiment commenced, the carnivorous bullfrog tadpoles started their feeding frenzy. They preyed on the two native species and even cannibalised each other. </p>
<p>This happened so quickly that only three of the pools were left with any surviving native tadpoles in the first week. The native tadpoles had been completely exterminated from the mixed species pools by the third week.</p>
<p>Bullfrog tadpoles grew with each hunt, enabling them to prey upon even more hapless native tadpoles. When left to themselves, the native tadpoles did much better, with three in every four making it to the finish line of metamorphosis – that is, they eventually turned into frogs.</p>
<p>The bullfrog tadpoles were so voracious that we weren’t even able to answer one of our questions: Would bullfrogs slow down native tadpoles’ growth? That’s because we had no native tadpoles left to measure.</p>
<p>The Chakrapani’s narrow-mouthed frog and the Andaman tree frog tadpoles that were kept away from the chomping bullfrog tadpoles transformed into terrestrial juveniles (known as metamorphs) in 21 days and 38 days, respectively. </p>
<h2>What this means</h2>
<p>Our experiment reveals that in natural conditions, native frogs – many of which breed in similar habitats as invasive bullfrogs – are highly vulnerable as tadpoles. </p>
<p>The findings also emphasise the potential impact that invasive bullfrog tadpoles can have at the level of populations. They can severely reduce the number of freshly minted metamorphs joining the native species populations. Of course, the situation is made more complicated in natural settings by the presence of other predators like dragonflies; and the availability of alternative food sources like mosquito larvae. </p>
<p>Still, our results suggest that the tadpole stage of Indian bullfrogs is to be taken seriously while understanding the impact of the species on native frogs. This may have implications elsewhere: the world is witnessing an accelerating rate of frog <a href="https://www.nature.com/articles/ncomms14435">invasions</a>. Invasive frog populations’ tadpoles could have a serious, damaging impact far beyond the Andamans.</p><img src="https://counter.theconversation.com/content/114845/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nitya Mohanty received funding for this work from the Center for Invasion Biology, Department of Botany and Zoology, Stellenbosch University and the Rufford foundation. </span></em></p>A new study reveals that it’s not only adult bullfrogs that pose a threat but their tadpoles do, too.Nitya Mohanty, Post-doctoral fellow Centre for Invasion Biology (C·I·B) Department of Botany & Zoology, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.