tag:theconversation.com,2011:/id/topics/bioacoustics-8394/articlesBioacoustics – The Conversation2023-05-23T00:15:39Ztag:theconversation.com,2011:article/2052232023-05-23T00:15:39Z2023-05-23T00:15:39ZGood vibrations: how listening to the sounds of soil helps us monitor and restore forest health<figure><img src="https://images.theconversation.com/files/526930/original/file-20230518-12204-6wif25.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4307%2C2851&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.pxfuel.com/en/free-photo-xnwfk">pxfuel</a></span></figcaption></figure><p>Nurturing a forest ecosystem back to life after it’s been logged is not always easy. </p>
<p>It can take a lot of hard work and careful monitoring to ensure biodiversity thrives again. But monitoring biodiversity can be costly, intrusive and resource-intensive. That’s where ecological acoustic survey methods, or “ecoacoustics”, come into play. </p>
<p>Indeed, the planet sings. Think of birds calling, <a href="https://www.sciencedirect.com/science/article/abs/pii/S0169534706000218?casa_token=o5SOujsJEcMAAAAA:DGMMfg-Le6QaVPY756llqYodbVZi5hlji-MQ8wNdOFn7dMBOOeT9emo8flURI6x3c7GMLKtx3A">bats echolocating</a>, tree leaves fluttering in the breeze, frogs croaking and bush crickets <a href="https://link.springer.com/article/10.1007/s00114-021-01749-7">stridulating</a>. We live in a euphonious theatre of life. </p>
<p>Even the creatures in the soil beneath our feet emit unique vibrations as they navigate through the earth to commute, hunt, feed and mate.</p>
<p>Eavesdropping on this subterranean cacophony using special microphones can provide researchers with important insights into ecosystem health. Our <a href="https://onlinelibrary.wiley.com/doi/10.1111/rec.13934">new study</a> published in Restoration Ecology shows ecoacoustics can provide an effective way of monitoring biodiversity in soil and in the forest it supports. </p>
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Read more:
<a href="https://theconversation.com/restoring-forests-often-falls-to-landholders-heres-how-to-do-it-cheaply-and-well-204123">Restoring forests often falls to landholders. Here's how to do it cheaply and well</a>
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<img alt="" src="https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525045/original/file-20230509-15-uslr52.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">
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<span class="caption">Setting up the ecoacoustics field trial.</span>
<span class="attribution"><span class="source">Jake M. Robinson</span>, <span class="license">Author provided</span></span>
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<h2>What did the study do?</h2>
<p>Acoustic technology is widely used to survey bats, birds and other creatures. However, scientists who restore degraded ecosystems have yet to make full use of soil ecoacoustics. This is despite its demonstrable effectiveness at detecting small animal vibrations.</p>
<p>Our study applied ecoacoustic tools to measure biodiversity above and below ground in a UK forest. We hypothesised that the soils of forests restored to a healthier state would have a higher diversity of sounds than the soils of recently deforested plots. This is because we assumed more creatures would live in the restored and “healthier” soils, producing a greater variety of sounds that we would detect. </p>
<p>Think of two symphony orchestras. Half of one orchestra’s musicians have fallen ill and can’t play at the concert. This is analogous to a degraded ecosystem. In contrast, the other orchestra has all its members and will therefore be louder, with more complex and diverse sounds.</p>
<p>During the spring and summer of 2022, we collected 378 samples from three recently deforested and three restored forest plots. We created a recording system with special “contact” microphones that we inserted into the ground. </p>
<p>We used a chamber with sound-dampening foam inside to record soil creatures such as earthworms and beetles. This chamber allowed us to block out unwanted signals such as mechanical noise, wind and human activity. The chamber housed the microphone and a 5 litre sample of the soil at each plot.</p>
<p>Our results were exciting. The diversity of sounds was much higher in the soil from the restored plots. This finding confirmed our suspicions that healthier soil would be more tuneful. </p>
<figure class="align-center ">
<img alt="Earthworms making tunnels through soil" src="https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526433/original/file-20230516-23-ofar3e.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">
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<span class="caption">Earthworms make sounds as they digest organic matter and tunnel through the soil.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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Read more:
<a href="https://theconversation.com/how-technology-allows-us-to-reveal-secrets-of-amazonian-biodiversity-182077">How technology allows us to reveal secrets of Amazonian biodiversity</a>
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<h2>Why is monitoring soil health important?</h2>
<p>Our preliminary findings suggest ecoacoustics can monitor life underground. But why is monitoring soil biodiversity so important? Soil health is the foundation of our food systems and supports all other <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/rec.13453?casa_token=7c9REV8s7m0AAAAA%3A8hfzqCbk1BIhUrRZSuqjsj442JnhcIPBGkNT3XmMZRbfi43XbIhLkfFmx47HEaDBTeEsS7finQnOEII">life on land</a>. It should be a global priority.</p>
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<a href="https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Australian magpie cocking its head to one side as it listens for worms in the soil" src="https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=901&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=901&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=901&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526439/original/file-20230516-15-mt7dsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&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">Birds, including Australian magpies, are known to listen for worms. Scientists can also use the sounds of the soil to assess its health.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>The “unseen” and “unheard” organisms living in the soil maintain its health. Below-ground organisms, such as earthworms and beetles, play a crucial role in <a href="https://link.springer.com/chapter/10.1007/978-0-387-74943-3_8">nutrient cycling</a> and soil health. Without them, forests can’t thrive. </p>
<p>By using ecoacoustics to monitor below-ground biodiversity, ecologists can better assess the effectiveness of restoration efforts. This will allow them to make more informed decisions about the best ways to protect nature.</p>
<p>Using ecoacoustics in restoration efforts could also have important implications for climate change mitigation. Forests are crucial <a href="https://www.nature.com/articles/s41467-021-22459-8">carbon sinks</a>. They absorb CO₂ from the atmosphere and store it in their woody biomass and soils. </p>
<p>In contrast, degraded or deforested areas are significant sources of <a href="https://www.lse.ac.uk/granthaminstitute/explainers/whats-redd-and-will-it-help-tackle-climate-change/#:%7E:text=When%20deforestation%20occurs%2C%20much%20of,Africa%2C%20followed%20by%20South%20America.">carbon emissions</a>. Restoring these areas and monitoring subterranean life can help reduce carbon emissions and improve our ability to reduce the effects of a changing climate.</p>
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Read more:
<a href="https://theconversation.com/no-more-excuses-restoring-nature-is-not-a-silver-bullet-for-global-warming-we-must-cut-emissions-outright-186048">No more excuses: restoring nature is not a silver bullet for global warming, we must cut emissions outright</a>
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<h2>It’s still an emerging science</h2>
<p>The use of ecoacoustics in restoration efforts is still relatively new, but it’s an important step towards a more holistic and effective approach to ecosystem recovery. By embracing new technologies and approaches, we can work towards a healthier and more sustainable planet.</p>
<p>Of course, there are challenges we still have to overcome. For instance, accurately identifying the sources of acoustic signals in a complex soundscape can be challenging. However, as technologies and methods continue to improve, the potential benefits of ecoacoustics are immense.</p>
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<img alt="" src="https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525048/original/file-20230509-23-oxr0m9.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">
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<span class="caption">When a forest like this temperate woodland in the UK is healthy, it acts as a carbon sink.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/photos/bluebell-woods-bluebells-oak-forest-5069304/">Pixabay</a></span>
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<p>By monitoring life underground in a non-intrusive and efficient way, we can better understand the effectiveness of our restoration efforts. This will help us make more informed decisions about how to protect nature. </p>
<p>We’ve only just begun to scratch the surface when it comes to the possibilities of ecoacoustics in restoration efforts. It’s an exciting time for those working in this field, as we discover new ways to use sound to heal our planet.</p>
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Read more:
<a href="https://theconversation.com/soil-abounds-with-life-and-supports-all-life-above-it-but-australian-soils-need-urgent-repair-187280">Soil abounds with life – and supports all life above it. But Australian soils need urgent repair</a>
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<img src="https://counter.theconversation.com/content/205223/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jake M Robinson is affiliated with the UNFCCC Resilience Frontiers think tank. </span></em></p><p class="fine-print"><em><span>Carlos Abrahams works for Baker Consultants, an ecological consultancy that specialises in ecoacoustics. He currently receives research funding from the UK Government.</span></em></p><p class="fine-print"><em><span>Martin Breed receives funding from the Australian Research Council, Cooperative Research Centre for Transformations in Mining Economies (CRC TiME), Australian Academy of Science, and New Zealand Ministry of Business, Innovation & Employment.</span></em></p>Acoustic technology allows us to listen to the sounds produced by the creatures in forest soils. A new study shows it’s a reliable way to monitor the biodiversity and health of the soil and forest.Jake M Robinson, Ecologist and Researcher, Flinders UniversityCarlos Abrahams, Senior Lecturer in Environmental Biology - Director of Bioacoustics, Nottingham Trent UniversityMartin Breed, Associate Professor in Biology, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1784602022-03-13T12:28:31Z2022-03-13T12:28:31ZGrunts, boops, chatters and squeals — fish are noisy creatures<figure><img src="https://images.theconversation.com/files/451103/original/file-20220309-27-15kx6jd.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C4980%2C3302&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">FishSounds is an online database of recordings of the noises created by fish, like this Bocon toadfish.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>While they may lack some of the melodic qualities of birds or whales, there are almost 1,000 species of fish that use sounds to communicate, and possibly many more. </p>
<p>Yet, despite nearly 150 years of contemporary scientific research into fish sound production, there was no global inventory of fish species known to make sounds. <a href="https://rdcu.be/cHjAQ">Until now</a>. Fish are one of the largest groups of sound-producing vertebrates, with speculated sound production abilities in thousands of the 34,000 fish species globally. </p>
<p>Our research team, led by Audrey Looby, conducted a systematic review examining almost 3,000 references. We extracted data from more than 800 different studies to determine that 989 fish species have been shown to produce active sounds globally. We used our findings to create <a href="https://fishsounds.net/index.js">FishSounds</a>, an online database cataloguing fish sounds.</p>
<h2>Wait, fish make sounds?</h2>
<p>While fish sound production may not be as widely recognized as it is for birds, frogs, bats or whales, people have known fish could make sounds for a very long time. <a href="http://classics.mit.edu/Aristotle/history_anim.4.iv.html">Fish sound production and possible fish hearing were discussed by Aristotle</a> more than 2,000 years ago. And looking at the common names of many fishes — like grunts, croakers and drums — it is clear fishers have known about their sounds for a long time, too.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/POITH02VVrw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A BBC Earth report on fish sounds.</span></figcaption>
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<p>Fish also have a wide diversity of <a href="https://doi.org/10.1111/faf.12217">mechanisms for their sound production</a>. Instead of vocal cords, fish may have adapted bony structures that they can rub or click together, while others use their swimbladder like a drum. Some fish even make sounds by expelling air out of their backsides. Yes, communication through “<a href="https://www.science.org/content/article/farting-fish-keep-touch">fish farting</a>.”</p>
<p>Fish may use sound to communicate information about <a href="https://doi.org/10.1016/j.anbehav.2006.04.014">reproduction</a>, <a href="https://doi.org/10.1111/eth.12180">their territory</a> or <a href="https://doi.org/10.1111/j.1095-8649.2004.00443.x">their food</a>. Because sound travels faster in water than in air, fish can <a href="https://doi.org/10.1134/s0032945209110010">hear signals across greater distances</a>, and faster than they could through sight, smell or taste. </p>
<p>For some examples, listen to the <a href="https://fishsounds.net/recording.js?id=07e8f3c9-0b19-4817-82e7-8782dd41b7a6">complex calls of the Bocon toadfish</a>, the <a href="https://fishsounds.net/recording.js?id=7a29e48b-4087-482f-83ec-e7a6aeda791d">ticks of the sablefish</a> and a <a href="https://fishsounds.net/recording.js?id=fb48adb1-65f1-41fa-b676-04117a49253a">chorus of freshwater drums</a>.</p>
<p>Thanks to our review, we are now able to detail which and how many fish species have been documented to use sound for communication. Actively soniferous — sound-producing — fishes have been found in marine, freshwater and brackish (slightly salty, like where rivers meet saltwater) environments in almost every region globally. They have also been found <a href="https://doi.org/10.1643/i2020172">throughout the fish taxonomic tree</a>, in 133 of the 549 fish families.</p>
<h2>Listening to fish</h2>
<p>Many other animals, including <a href="https://doi.org/10.1007/s00114-017-1467-3">birds</a>, <a href="https://doi.org/10.1016/j.anbehav.2004.06.020">dolphins</a> <a href="https://doi.org/10.1098/rspb.2014.0715">and crabs</a> may eavesdrop on fish sounds to eat, avoid being eaten and navigate to suitable habitats.</p>
<p>Underwater animals aren’t the only ones who can eavesdrop on fish sounds. We used a remote sensing technique called <a href="https://doi.org/10.1577/1548-8446(2006)31%5b433:LTF%5d2.0.CO;2">passive acoustics</a> to record underwater sounds and learn more about fish and their environment.</p>
<p>Fish sounds have been used to <a href="https://doi.org/10.1007/s10530-017-1419-z">detect invasive species</a>, <a href="https://doi.org/10.1007/s00227-013-2324-3">monitor spawning</a> and <a href="https://doi.org/10.1577/t07-106.1">identify essential habitats</a>. Fish chewing sounds have even been used in aquaculture <a href="https://doi.org/10.1016/s0044-8486(00)00375-6">to optimize feeding</a>.</p>
<p>There is also a growing body of evidence that human activities through <a href="https://doi.org/10.1126/science.aba4658">noise pollution</a>, <a href="https://doi.org/10.1073/pnas.1719291115">habitat degradation</a> and <a href="https://doi.org/10.1371/journal.pone.0170838">climate change</a> are hurting the abilities of fish to produce and hear critical sounds for their reproduction and survival. This has potentially detrimental effects to whole populations or communities of fish.</p>
<p>Using our global review of soniferous fishes as a framework, FishSounds makes the data we collected available to other researchers, and anyone else, with an interest in aquatic ecosystems. Users can search by species, recording or study information. We also provide information about our data and links to other relevant websites.</p>
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<a href="https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&rect=0%2C21%2C2044%2C1505&q=45&auto=format&w=1000&fit=clip"><img alt="A red spotted fish on a black background" src="https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&rect=0%2C21%2C2044%2C1505&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/451097/original/file-20220309-13-154vgw3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">While fish don’t have vocal cords, they do produce sounds to communicate.</span>
<span class="attribution"><span class="source">(Kieran Cox)</span>, <span class="license">Author provided</span></span>
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<p>We are also compiling recordings of the many sounds fish produce, with 239 recordings currently available, and many more to come.</p>
<h2>Growing resource</h2>
<p>We plan to expand our data offerings and functionalities, including regularly updating our database to include new research and recordings, implementing a form submission system that people can use to upload audio files of fish sounds and creating interactive searches that allow users to visualize trends in the data.</p>
<p>FishSounds is also collaborating with other data repositories and efforts, including <a href="https://www.fishbase.de/">FishBase</a>, as well as contributing to a <a href="https://doi.org/10.3389/fevo.2022.810156">global library of underwater biological sounds</a>.</p>
<p>Because more than 95 per cent of fish species lack published research on sound production, we hope to amplify what we know already and support future work on the wonderful world of fish sounds.</p><img src="https://counter.theconversation.com/content/178460/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amalis Riera works for MERIDIAN - the Marine Environmental Research Infrastructure for Data Integration and Application Network. This group receives funding from the Canada Foundation for Innovation (CFI), Research Nova Scotia, and Dalhousie University.</span></em></p><p class="fine-print"><em><span>Kieran Cox receives funding from Liber Ero Fellowship and the Natural Sciences and Engineering Research Council of Canada</span></em></p><p class="fine-print"><em><span>Sarah Vela works for MERIDIAN - the Marine Environmental Research Infrastructure for Data Integration and Application Network. This group receives funding from the Canada Foundation for Innovation (CFI), Research Nova Scotia, and Dalhousie University. </span></em></p><p class="fine-print"><em><span>Audrey Looby 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>Growing research shows that fish produce sounds that other creatures listen to to find food and avoid becoming prey. A new database compiles research on these fish sounds.Audrey Looby, PhD candidate, Fisheries and Aquatic Sciences, University of FloridaAmalis Riera, Research Scientist, Fisheries, University of VictoriaKieran Cox, Postdoctoral fellow, Marine Ecology, University of VictoriaSarah Vela, Senior Data Manager, Dalhousie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1782052022-03-01T15:04:40Z2022-03-01T15:04:40ZWhen a hippo honks, here’s what it could mean – to another hippo at least<figure><img src="https://images.theconversation.com/files/449227/original/file-20220301-25-1h8fu7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">shutterstock</span> </figcaption></figure><p>Hippos are very vocal animals, exchanging signals like the “wheeze honk”. But not much is known about what these sounds mean. Two researchers found themselves thinking about this in Mozambique – where they were initially studying crocodiles. </p>
<p>Hippos are quite territorial and aggressive – and fast-moving. So the researchers kept a fair distance away as they conducted their <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(21)01693-6?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982221016936%3Fshowall%3Dtrue">experiment</a>. They recorded hippo noises and played them back to the animals, watching to see how the hippos behaved. If the call came from an unknown hippo in a different social group, the response appeared to be aggressive. If the call was one they recognised, they were less inclined to be aggressive. </p>
<p>One way hippos show aggression is to spray dung.</p>
<p>The meaning of hippo sounds is useful to know for conservation efforts. Hippos and humans sometimes come into conflict and need to be moved for their own survival. Before relocating them, conservation managers could play them the sounds of the hippos they will be meeting in their new location, to familiarise them.</p>
<p>In this episode of Pasha, Nicolas Mathevon, professor in animal behaviour and bioacoustics at the University of Saint-Etienne, and Paulo Fonseca, professor in acoustic communication at the University of Lisbon, take us through their experiences of listening to hippos in Mozambique.</p>
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<p><strong>Photo</strong>
“Specie Hippopotamus amphibius family of Hippopotamidae.” by PACO COMO, found on <a href="https://www.shutterstock.com/image-photo/hippopotamus-kruger-national-parksouth-africa-specie-439875586">Shutterstock</a> </p>
<p><strong>Music</strong>
“Happy African Village” by John Bartmann, found on <a href="http://freemusicarchive.org/music/John_Bartmann/Public_Domain_Soundtrack_Music_Album_One/happy-african-village">FreeMusicArchive.org</a> licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1</a>.</p>
<p>“African Moon” by John Bartmann, found on <a href="http://freemusicarchive.org/music/John_Bartmann/Public_Domain_Soundtrack_Music_Album_One/happy-african-village">FreeMusicArchive.org</a> licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1</a>.</p>
<p><em>The researchers would like to thank the Maputo special reserve for allowing them to do the research on the property.</em></p><img src="https://counter.theconversation.com/content/178205/count.gif" alt="The Conversation" width="1" height="1" />
Hippos are very vocal creatures. They display certain aggressive behaviour when strangers are in their territory.Ozayr Patel, Digital EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1778062022-02-24T19:09:42Z2022-02-24T19:09:42ZListening to everything: how sound reveals an unseen world<figure><img src="https://images.theconversation.com/files/448207/original/file-20220224-23-lp329f.jpeg?ixlib=rb-1.1.0&rect=7%2C0%2C5168%2C3453&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Lawrence English</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Vision is often regarded as first among the human senses, as our eyes are the way most of us come to know the world. However, vision has its limits.</p>
<p>Even now, as you use your eyes to read this, other senses are in operation that open up a greater appreciation of the world. Perhaps the most powerful of these is listening - audition.</p>
<p>Sound carries cues about the world we might otherwise miss. And with the development of new technologies and the work of dedicated scientists and artists, we can today listen to what was previously unimaginable, from the inner workings of plants to catastrophes in distant galaxies. </p>
<iframe style="border: 0; width: 100%; height: 42px;" src="https://bandcamp.com/EmbeddedPlayer/album=261091851/size=small/bgcol=ffffff/linkcol=0687f5/track=2147495075/transparent=true/" seamless="" width="100%" height="400"><a href="https://lawrenceenglish.bandcamp.com/album/songs-of-the-living">Songs Of The Living by Lawrence English</a></iframe>
<p>In my own work, <a href="https://www.museumofbrisbane.com.au/making-place-site-listening/">currently exhibited at the Museum of Brisbane</a>, I have made <a href="https://lawrenceenglish.bandcamp.com/album/songs-of-the-living">field recordings</a> of environments and creatures around the world. These works take their place alongside an ever-growing collection of recordings revealing the unheard sounds of our world.</p>
<h2>The limits of the ear</h2>
<p>Humans can only <a href="https://www.ncbi.nlm.nih.gov/books/NBK10924/">hear a limited range of sounds</a>: those with frequencies between about 20 hertz (low sounds like thunder) and 20 kilohertz (very high sounds like some species of bats). Other sounds exist outside the scope of our auditory capacities. </p>
<p>“Infrasonic” sounds such as the rumble of earthquakes have frequencies too low for us to perceive, although <a href="https://sos.noaa.gov/education/phenomenon-based-learning/can-elephants-sense-tsunamis/#:%7E:text=Tsunamis%20are%20large%20waves%20created,can%20sense%20the%20vibrations%20earlier">other animals can detect them</a>. There are “ultrasonic” sounds too, with frequencies above the threshold of human hearing.</p>
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Read more:
<a href="https://theconversation.com/listening-to-the-ocean-reveals-a-hidden-world-and-how-we-might-save-it-173790">Listening to the ocean reveals a hidden world – and how we might save it</a>
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<p>Strictly speaking, a sound is a vibration in air. But we can also think of other kinds of vibrations, such as electromagnetic waves, as having the potential to be registered as sounds. </p>
<p>With the right kind of technological translation tools, you can hear the electromagnetic sounds emitted by devices like the one on which you are reading this right now.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/muGAokcUksI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The ‘Stereo Bugscope’ created by the artist Haco amplifies the sounds of electronic circuitry.</span></figcaption>
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<h2>Why should we listen?</h2>
<p>Listening is a different way of knowing the world that expands our understanding. Sound travels around corners and through walls, from places that are out of sight.</p>
<p>Our ears are a gateway to a deeper sensing of the world. Take bird calls, for example.</p>
<p>For most, even those of us living in densely populated urban centres, dawn’s arrival is trumpeted by a chorus of bird calls. These voices, that seemingly splay out in all directions suggest acts of territorial dominance, of the seeking and discovery of food and other fundamental activities of animal species. A variation of the chorus occurs again, as the sun vanishes over the horizon. </p>
<p>These daily occurrences are so commonplace as to not draw themselves to attention. But on closer examination, we are discovering they reveal much about <a href="https://dawn-chorus.org/idea/">habitat health, seasonality and other environmental markers</a>. </p>
<h2>Listening longer, listening deeper, listening wider</h2>
<p>Today we are listening to more of the world, and beyond, than ever before, with the growth of disciplines such as <a href="https://www.wildlifeacoustics.com/resources/bioacoustics">bio-acoustics</a>, <a href="https://science.nasa.gov/ems/05_radiowaves">radio telescopy</a>, and more philosophical fields such as <a href="https://www.youtube.com/watch?v=Bu2G6Iu38TM">sound studies</a>. </p>
<p>The proliferation of technologies such as <a href="https://oceanservice.noaa.gov/facts/hydrophone.html#:%7E:text=A%20hydrophone%20is%20an%20underwater,reproduction%2C%20and%20to%20seek%20prey.">hydrophones</a> (underwater microphones) and <a href="https://www.youtube.com/watch?v=XZLZ48DGjwc">electromagnetic receivers</a> has also increased the reach of our ears. </p>
<p>It’s this combination of intellectual, scientific and artistic curiosity, matched with technological developments and availability that have resulted in the capture of some incredible sound events that exist well beyond the visual plane. </p>
<p>Just a quarter of a century ago it seemed like science fiction that we might be able to capture the sound of <a href="https://www.ligo.caltech.edu/video/ligo20160211v2">two black holes colliding in space</a> – but scientists did it in 2015.</p>
<p><audio preload="metadata" controls="controls" data-duration="11" data-image="" data-title="The sound of black holes colliding: gravitational waves converted to sound waves." data-size="166921" data-source="Caltech / MIT / LIGO Lab" data-source-url="https://www.ligo.caltech.edu/video/ligo20160211v2" data-license="" data-license-url="">
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The sound of black holes colliding: gravitational waves converted to sound waves.
<span class="attribution"><a class="source" rel="nofollow" href="https://www.ligo.caltech.edu/video/ligo20160211v2">Caltech / MIT / LIGO Lab</a><span class="download"><span>163 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/2414/ligo20160211v2.m4a">(download)</a></span></span>
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<p>These discoveries and others like them have fostered new research programs that aim to undertake the deepest and most concentrated <a href="https://www.theguardian.com/science/2015/jul/20/breakthrough-listen-massive-radio-wave-project-scan-far-regions-for-alien-life">galactic listening</a> to date.</p>
<h2>As above, so below</h2>
<p>We have made many discoveries closer to home, too. </p>
<p>We have known for a long time that the underwater world is rich in sounds, but it has been underrepresented in dedicated research. This trend is changing, with numerous <a href="https://www.theguardian.com/science/2022/feb/19/fish-acoustic-communication-sex-food-researchers">studies</a> highlighting the rich acoustic diversity of rivers, oceans and reefs. </p>
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<img alt="" src="https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/448213/original/file-20220224-17-1a3hk6z.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">
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<span class="caption">Plants may use the sound of water to guide the growth of their roots.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>On land, the Australian researcher Monica Gagliano has explored <a href="https://www.news.uwa.edu.au/archive/201704119544/research/study-reveals-plants-listen-find-sources-water/">plant audition</a>. She demonstrated how plants can use sound to find water – so next time your plumbing is blocked by a plant’s roots, keep in mind they have been listening to the water flowing through the pipes.</p>
<p>Equally profound are the studies of bioelectrical sounds emitted by plants carried out by artists such as the Irish “sound ecologist” Michael Prime. For several decades, Prime has catalogued various <a href="https://michaelallenzprime.bandcamp.com/album/one-hour-as-peyote">bioelectric emissions from plants</a>. At times they resemble unsettled but rhythmic avant-garde music.</p>
<h2>Field recording</h2>
<p>This curiosity for listening into places and those that inhabit them, has also spawned a zone of creative sound practice called <a href="https://www.factmag.com/2014/11/18/a-beginners-guide-to-field-recording/">field recording</a>. A field recordist is a listener who is primarily focused on capturing the sonic aspects of environments that captivate them. </p>
<p>Once a marginal part of the sound arts canon, field recording has come to be regarded as a critical field of creative engagement. This year artists such as Philip Samartzis have been memorialised in a series of <a href="https://www.rmit.edu.au/news/all-news/2021/mar/antarctic-stamps">Australian Antarctic postage stamps</a>.</p>
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Read more:
<a href="https://theconversation.com/the-sounds-around-us-an-introduction-to-field-recording-36494">The sounds around us: an introduction to field recording</a>
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<p>Even if you don’t want to make your own field recordings, you might be interested in listening to the sound walks of Canadian artist <a href="https://www.youtube.com/watch?v=hg96nU6ltLk">Hildegard Westerkamp</a>, or experiencing the situational listening of Japanese artist Akio Suzuki’s <a href="https://www.sbs.com.au/language/english/audio/let-s-turn-the-bustle-of-melbourne-into-music-akio-suzuki">Oto Date</a> project. </p>
<p>These works, like my own <a href="https://www.museumofbrisbane.com.au/making-place-site-listening/">Site Listening</a> at the Museum Of Brisbane, recognise that the more we listen into the world around us, the more we realise we are yet to hear its true resonances.</p><img src="https://counter.theconversation.com/content/177806/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lawrence English 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>From the bioelectric bleeps of plants to the intergalactic bloops of colliding black holes, sound gives us new ways to experience the world.Lawrence English, Adjunct Research Fellow, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1755272022-01-26T15:11:58Z2022-01-26T15:11:58ZEavesdropping on nature: why Africa needs more bioacoustics research<figure><img src="https://images.theconversation.com/files/442185/original/file-20220124-25-6h373i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">African Penguins are among the species affected by noises made by seismic underwater exploration.</span> <span class="attribution"><span class="source">Sergey Uryadnikov/Shutterstock</span></span></figcaption></figure><p>Sound plays an important role in nature. It also helps researchers to study and interpret different landscapes and the species that live there. Most animals make sound; biologists often rely on chirps, squawks or whistles to describe and identify species or groups of species. They can also extract behavioural information from sound. For instance, researchers have found that the yellow-casqued hornbill in West Africa can <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2003.2619">distinguish predator-specific alarm calls</a> made by Diana monkeys. </p>
<p>Vocalisations can also simply indicate a species’ presence. A recording process called <a href="https://academic.oup.com/bioscience/article/69/1/15/5193506">passive acoustic monitoring</a> recently revealed the <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/aqc.2973?casa_token=cArb1mhAqdsAAAAA%3Axup53SXtkn_XwNIYbtc0g-BzmIV3TyHJzgvMPSG3r8xxQ5r7vVb0wilRieAWeTEULHtVIhnGBQ0BcOhL">presence of the cusk-eel</a>, an elusive fish species, in a marine protected area in the Adriatic Sea.</p>
<p>The study of biological sound produced, transmitted or perceived by animals, both on land and in water, is called <a href="https://www.washingtonpost.com/science/with-bioacoustics-conservationists-try-to-save-birds-through-their-songs/2020/01/10/8b800048-0c9a-11ea-bd9d-c628fd48b3a0_story.html">bioacoustics</a>. The discipline can be traced back to the 1920s; it was formalised with the establishment of the <a href="https://www.ibac.info/">International Committee for Bioacoustics in 1956</a>. </p>
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Read more:
<a href="https://theconversation.com/experience-the-spectacular-sounds-of-a-murrumbidgee-wetland-erupting-with-life-as-water-returns-174423">Experience the spectacular sounds of a Murrumbidgee wetland erupting with life as water returns</a>
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<p>There are several advantages to sound as a study mechanism. Automated recording processes bolstered by technology allow scientists to record at remote sites or for extended periods of time. These processes also eliminate the effect that a human’s presence might have on their surroundings. And as technology has improved, recording devices have become more affordable for researchers and citizen scientists alike.</p>
<p>My co-authors and I <a href="https://www.tandfonline.com/doi/abs/10.1080/09524622.2021.2021987?journalCode=tbio20">set out to assess</a> the state of bioacoustics research on the African continent. Our aim was to create a roadmap to help guide future work within the discipline on the continent. We analysed 727 publications – relatively broad, given that nothing of this scale had previously been done – dating from 1953 to mid-2020. </p>
<p>We found that most of the research related to land rather than marine or freshwater animals. We also found that eastern and southern Africa dominated the output for this discipline – but that a majority of researchers came from outside the continent. African-affiliated researchers have started closing that gap in the past 20 years. </p>
<p>There is plenty of work to do to ensure that other species, geographical areas and ecosystems across Africa are better understood through bioacoustics.</p>
<h2>Gaps highlight opportunities</h2>
<p>We accessed three major online databases and searched for scientific literature with varying keyword combinations. Publications that met our criteria were extracted and scanned for a range of information. This related largely to authorship, study site and study subject. Chronologically, the <a href="https://www.tandfonline.com/doi/abs/10.1080/00306525.1953.9633805">first piece</a> of research we identified dates back to 1953. In it, birdsong was used to describe spectacled weaver behaviour in South Africa. </p>
<p>Our record suggests that bioacoustics related research output has grown over time and especially since the turn of the millennium – in correlation with advances in technology and data storage. Nearly two-thirds of the studies we evaluated focused on mammals. </p>
<p>We detected biases within the mammalian class. Primate, and more specifically chimpanzee related research, has enjoyed a disproportionate amount of bioacoustics related attention. As a group, bats have also aroused considerable scientific curiosity; their echolocation behaviours are <a href="https://besjournals.onlinelibrary.wiley.com/doi/10.1111/2041-210X.13721?af=R">reliable species classifiers</a>. </p>
<p>A penchant for mammal-based research among biologists and ecologists <a href="https://www.nature.com/articles/s41598-017-09084-6">isn’t news</a>. But we are flagging it because it raises concerns that conservation efforts are heavily skewed towards some species. This leaves other species at risk.</p>
<p>Our findings also suggest that more bioacoustics attention needs to be directed towards non-terrestrial habitats. Land-based studies made up close to 90% of our entire record. This ought to be addressed, given what human activity has done to the world’s oceans and freshwater systems. </p>
<p>A <a href="https://www.science.org/doi/10.1126/science.aba4658">2021 review</a> published in the journal Science outlined the acoustic challenges our oceans face today. Along the South African coastline, for example, African penguins have been found to <a href="https://www.nature.com/articles/s41598-017-16569-x">evade noises</a> produced by the seismic exploration of gas and oil in the ocean. This has taken on even more relevance with oil giant Shell’s <a href="https://www.bbc.com/news/world-africa-59809821">recent attempts</a> to conduct exploratory activities near the country’s Wild Coast.</p>
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Read more:
<a href="https://theconversation.com/are-seismic-surveys-driving-penguins-from-their-feeding-grounds-90864">Are seismic surveys driving penguins from their feeding grounds?</a>
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<p>But it’s not just about assessing immediate threats. Acoustic monitoring can help supply high-quality data to regional or global biodiversity databases, which are designed to inform environmental management and policy. </p>
<p>We suggest that the comparatively slower uptake of underwater bioacoustics research on the African continent could be put down to the lack of affordable equipment and costs associated with deploying it. Equipment affordability issues are, at least, gradually being remedied through the development of <a href="https://www.sciencedirect.com/science/article/pii/S2468067219300306">more cost-effective technology</a>. </p>
<h2>Regional differences</h2>
<p>On land, African bioacoustics research has been concentrated in certain regions. East and Southern Africa have, to now, hosted a disproportionately large amount of bioacoustics themed research compared to the rest of the continent. North Africa was strikingly underrepresented in our study. </p>
<p>On a more localised scale, protected areas and their relative ease of access for researchers have been key drivers of regional bioacoustic research efforts in Côte d’Ivoire’s Taϊ National Park and Uganda’s <a href="https://royalsocietypublishing.org/doi/10.1098/rsos.172066">Budongo Central Forest Reserve</a>, for instance. These territories are well known for their primate populations, especially chimpanzees.</p>
<p>Critically, we weighed up African versus non-African affiliated contributions to the field. Authors attached to non-African institutions heavily outnumbered their African counterparts. African-affiliated contributors have only started closing that gap over the last 20 years or so.</p>
<h2>Building the field</h2>
<p>This research is meant to do more than just highlight gaps in the continent’s bioacoustics related output. Arguably more importantly, it was designed to aid, encourage and promote African capacity building and participation in an emerging field. This is in line with the work being undertaken by the <a href="https://africanbioacoustic.wixsite.com/abcommunity">African Bioacoustics Community</a>. The forum was established in 2018 to connect people working on bioacoustics on the African continent and is preparing to host its third ever conference this year.</p>
<p>Acoustic monitoring has been touted as a “<a href="https://www.sciencedirect.com/science/article/pii/S1877343520300592">key monitoring solution</a>” in the pursuit of answers to biodiversity questions. For Africa this spells boundless potential.</p>
<p><em>Fannie Shabangu, marine biologist, South African Department of Environment, Forestry and Fisheries; Tess Gridley, principal scientist, Sea Search Research and Conservation; Heiko Wittmer, associate professor, Victoria University of Wellington and Stephen Marsland, professor, Victoria University of Wellington co-authored the research on which this article is based.</em></p><img src="https://counter.theconversation.com/content/175527/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frowin Becker receives funding from the National Geographic Okavango Wilderness Project. </span></em></p>There is plenty of work to do to ensure that other species, geographical areas and ecosystems across Africa are better understood through bioacoustics.Frowin Becker, PhD Candidate, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1737902021-12-31T05:41:55Z2021-12-31T05:41:55ZListening to the ocean reveals a hidden world – and how we might save it<figure><img src="https://images.theconversation.com/files/438055/original/file-20211216-17-1xc7ru6.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2048%2C1363&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/52133016@N08/5565696408">USFWS Pacific/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>On summer evenings in the 1980s, the residents of a houseboat community in Sausalito, California would often have trouble sleeping. A bizarre and persistent humming noise would keep them awake, and although they investigated, neither the residents nor the local authorities could pinpoint the problem. </p>
<p>They ruled out noise from generators, and even considered the possibility of secret military tests. It was researchers at the nearby Steinhart Aquarium who finally <a href="https://coveringthecity.com/humming-toadfish-sausalito-california-mccosker-kgo-radio-sound/">identified the culprit</a>. The strange noise was the <a href="https://soundcloud.com/user-449258848/humming-toadfish-sound-2?utm_source=coveringthecity.com&utm_campaign=wtshare&utm_medium=widget&utm_content=https%253A%252F%252Fsoundcloud.com%252Fuser-449258848%252Fhumming-toadfish-sound-2">courtship song of male toadfish</a> who were doing their best to attract females to their underwater love nests.</p>
<p>Back then, the field of bioacoustics – the scientific study of the production, transmission and perception of animal sounds – was a highly specialised and relatively remote research area. Underwater bioacoustics was even more niche, with only a handful of labs having access to the expensive equipment and technical know-how needed to record and decipher aquatic soundscapes. </p>
<figure class="align-center ">
<img alt="Two people wearing life jackets on a boat lower a long, metal cylinder into the sea." src="https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438188/original/file-20211217-15-47gf99.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">Researchers lowering a hydrophone – a device for recording sound underwater – into the Atlantic Ocean.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Hydrophone#/media/File:Hydrophone_being_lowered_into_the_Atlantic.jpg">Dave Mellinger/Oregon State University</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Cheaper kits capable of more accurate recordings and powerful open source software have since brought the study of aquatic sounds to the scientific masses. This has led to a renaissance in our understanding of sound in the sea. And it turns out that the ocean is a very noisy place indeed.</p>
<h2>Life in an increasingly noisy ocean</h2>
<p>Scientists are now discovering the extent to which aquatic animals produce sound, and the role that their grunts, pops, growls and whines play in communication. </p>
<p>For instance, we now know that many commercially important fish species, like cod and haddock, choreograph their complex courtship displays by <a href="https://www.tandfonline.com/doi/abs/10.1577/T04-061.1">producing grunts and hums</a>. Sound plays an equally important role in the complex sex life of the noisy Caribbean coral reef fish, the black hamlet. These fish are simultaneous hermaphrodites and produce both sperm and eggs at the same time. They <a href="https://link.springer.com/article/10.1007/BF00010947">make noises during courtship</a> to signal to their partner whether they are temporarily acting as the “male” or the “female” as they trade sex cells.</p>
<figure class="align-center ">
<img alt="A dusky fish on a pink and white coral background." src="https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438189/original/file-20211217-25-7ck4vb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Black hamlet fish need sound in order to procreate properly.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/black-hamlet-fish-on-reef-1988318555">Joseph M. Bowen/Shutterstock</a></span>
</figcaption>
</figure>
<p>Evolution has adapted fish for life in environments where cues other than sound may be less reliable. When the water’s cloudy, if it’s dark, or if you live under a rock or an <a href="https://youtu.be/UUIe38jmcMc">upturned mollusc shell</a>, then even if your prospective mate can’t <em>see</em> you, they can still <em>hear</em> you, and use this to determine whether you might <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0064620">make a suitable partner</a>.</p>
<p>The problem for many marine animals now, though, is that the underwater soundscapes they have evolved in are being pummelled by broad-frequency noise from shipping, drilling and many <a href="https://www.science.org/doi/10.1126/science.aba4658">other human sources</a>. This makes it harder for them to be heard, and it’s not only their romantic encounters that are affected.</p>
<figure class="align-center ">
<img alt="A large passenger cruise ship with port in the background." src="https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438192/original/file-20211217-25-1l807ph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Industries are flooding the ocean with anthropogenic noise.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/miami-december-30-2018-royal-allure-1271143585">Lazyllama/Shutterstock</a></span>
</figcaption>
</figure>
<p>European eels are endangered fish that begin their lives in the Atlantic Ocean but migrate to rivers and lakes to undergo most of their growth and development, before returning to the sea to spawn. Recent studies have demonstrated that the noise they encounter around boat-crowded coasts can prevent them from reacting to predators and <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.12685">lessen their chances of survival</a>.</p>
<p>But it’s not just noisy human activity that stops animals reliant on underwater sound from surviving and prospering. Climate change is having a complex effect on underwater soundscapes, and nowhere is this more clear than on coral reefs. When <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.1996.tb00063.x">coral reefs bleach</a> in response to rising temperatures and <a href="https://www.pnas.org/content/105/45/17442">ocean acidity</a>, there’s usually a dramatic reduction in the noises emanating from these habitats.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/with-no-work-in-lockdown-tour-operators-helped-find-coral-bleaching-on-western-australias-remote-reefs-142644">With no work in lockdown, tour operators helped find coral bleaching on Western Australia’s remote reefs</a>
</strong>
</em>
</p>
<hr>
<p>On a healthy reef, the combined din of countless snapping shrimps, grunting gobies and other noisy coral critters creates an acoustic signpost which prospective larval reef dwellers drifting on oceanic currents use to navigate towards suitable habitats to settle on. As the noisy occupants desert an unhealthy reef and the sound levels drop, the recruitment of incoming animals falls too, accelerating the <a href="https://www.pnas.org/content/115/20/5193">reef’s death</a>. </p>
<p>So far, so depressing. But here’s the good news. Our improved understanding of underwater sounds on coral reefs might help scientists keep track of how these ecosystems are faring. In a <a href="https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.14089">recent paper</a> led by the Universities of Exeter and Bristol, researchers studied coral reefs that had been extensively damaged by blast fishing – a dangerous and destructive technique in which explosives are used to stun and catch fish. They monitored the reef’s recovery after being artificially restored with new healthy corals. As these devastated reefs recovered, the quantity and diversity of sounds they recorded began to match those of pristine reefs.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/97M2muq9JQc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Even better, we can use this knowledge to help damaged coral reefs recover quicker. Using underwater speakers, scientists have been able to play back sounds recorded on healthy reefs to entice fish and other animals back to <a href="https://www.nature.com/articles/s41467-019-13186-2">recovering coral habitats</a>, speeding up the natural process of regeneration.</p>
<p>By listening to the ocean, we have begun to truly understand – and tentatively address – the many challenges it faces.</p><img src="https://counter.theconversation.com/content/173790/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Iain Barber 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>The ocean is naturally noisy. Here’s what all the buzz is about.Iain Barber, Deputy Dean, School of Animal, Rural & Environmental Sciences, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1724242021-11-24T14:35:26Z2021-11-24T14:35:26ZWhat bush crickets are telling researchers via their unique calls<figure><img src="https://images.theconversation.com/files/433488/original/file-20211123-21-nbfu2t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">T thyraeus</span> </figcaption></figure><p>Bush crickets – or katydids, as they are also known – are fascinating creatures. They belong in the same order of insects as grasshoppers and crickets and are among the many species that communicate acoustically.</p>
<p>Male bush crickets are prolific callers – and each species has its own call to advertise their fitness to females. They call in different frequency bands and for different lengths of time, so that they can make themselves heard to the right potential mate. </p>
<p>In South Africa, there are about 169 species of bush crickets. Of these, about 123 have an <a href="https://www.iucnredlist.org/">IUCN Red List</a> status. The species <em>Thoracistus thyraeus</em> is considered critically endangered. But a study by our guest in today’s episode of Pasha, Aileen van der Mescht, a postdoctoral researcher at the department of zoology and entomology at the University of the Free State, found that they might be more resilient than was thought. </p>
<p>She recorded the calls of nocturnal bush crickets to determine how the different species were distributed across the landscape and what variables drive the distribution. The <a href="https://www.tandfonline.com/doi/abs/10.1080/09524622.2021.1925589">research</a> identified 11 species in the study area. Those that used a higher frequency for their specific call tended to be recorded in more open habitats like grassland. Lower frequency callers occupied woodier areas – both plantations and indigenous forests. <em>Thoracistus thyraeus</em> was present in a forestry plantation where it wasn’t expected to be.</p>
<p><em>Thoracistus thyraeus</em> is also known as the Inflated Seedpod Shieldback. Its blown-up thorax looks like a seedpod and amplifies its call. </p>
<p>Bush crickets are often well camouflaged to avoid being eaten by predators. They feature in many food webs and play an important role in recycling nutrients. Aileen talks about some of their interesting features and their <a href="https://theconversation.com/pasha-121-why-we-need-mosquitoes-166430">value</a> in ecosystems. </p>
<hr>
<p><strong>Photo:</strong><br>
“Male, Thoracistus thyraeus in KwaZulu Natal, Karkloof swamp.”
by Claudia Hemp found <a href="http://orthoptera.speciesfile.org/Common/basic/ShowImage.aspx?TaxonNameID=1141648&ImageID=196109">here</a></p>
<p><strong>Music:</strong>
“Happy African Village” by John Bartmann, found on <a href="http://freemusicarchive.org/music/John_Bartmann/Public_Domain_Soundtrack_Music_Album_One/happy-african-village">FreeMusicArchive.org</a> licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1</a>.</p>
<p>“One Night In Africa” by John Bartmann, found on <a href="https://freemusicarchive.org/music/John_Bartmann/Royalty-Free_Soundtrack_Music_Album_Two/one-night-in-africa">Free Music Archive</a> licensed under under a <a href="https://creativecommons.org/licenses/by-sa/4.0/">Attribution-ShareAlike License</a>.</p><img src="https://counter.theconversation.com/content/172424/count.gif" alt="The Conversation" width="1" height="1" />
The ears of bush crickets are found on their forelegs.Ozayr Patel, Digital EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1715132021-11-23T14:17:08Z2021-11-23T14:17:08ZStatistical ecology can unlock the power of biodiversity data in Africa<figure><img src="https://images.theconversation.com/files/431906/original/file-20211115-23-473371.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Statistical techniques are often used to show where poaching actually happens.</span> <span class="attribution"><span class="source">Wildsnap/Shutterstock</span></span></figcaption></figure><p>Africa boasts an immensely rich diversity of <a href="https://www.nature.com/articles/ncomms9221/?fbclid=IwAR2yFlI5lvfwAuEp7Bl9PnnjLVcE7SpVt18IuOTJxBTpT-VJx4HMKJAAzhc">plant and animal species</a>. These are the building blocks of healthy ecosystems. Yet, <a href="https://www.nature.com/articles/s41558-019-0406-z">the projected loss</a> of wild habitats and species on the continent threatens biodiversity. Recent reports by the Intergovernmental Panels on <a href="https://zenodo.org/record/5657041#.YYwLgWBBxPY">Biodiversity and Ecosystem Services</a> and <a href="https://www.ipcc.ch/report/ar6/wg1/">Climate Change</a> also highlight how biodiversity loss and climate change threaten human well-being.</p>
<p>Good information is crucial to understand and reverse this trend. More and more data about biodiversity is becoming available worldwide, through satellite imagery, <a href="https://www.frontiersin.org/articles/10.3389/fclim.2021.650760/full">citizen science programmes</a> and wildlife rangers, for example. But socio-ecological systems are enormously complex and so data can still be sparse, biased, or incomplete. Not only must data be collected, it also has to be analysed if it is to be useful for decision making.</p>
<p>The emerging field of <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-statistics-022513-115633">statistical ecology</a> offers great promise to meet these challenges. This discipline uses growing datasets and innovative analytical methods to tackle important questions in biodiversity science and management. Statistical ecology offers <a href="https://jrsbiodiversity.org/our-programs/capacity/">opportunities</a> for African researchers to develop local solutions to the continent’s ecological challenges. It is currently a fast developing field, even in Africa where it is led mostly by active research groups in South Africa. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two graphs showing ecology and statistics" src="https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=255&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=255&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=255&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=320&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=320&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431011/original/file-20211109-25-1eqn7ew.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=320&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 recent development of the field of statistical ecology as compiled from Web of Science (a) per publications worldwide, and (b) per institutions working on African data. African institutions are shown in orange, although others have delegations in Africa.</span>
<span class="attribution"><span class="source">Henintsoa Onivola Minoarivelo</span></span>
</figcaption>
</figure>
<p>Our aim at the centre for <a href="http://www.seec.uct.ac.za/">Statistics in Ecology, Environment and Conservation</a> at the University of Cape Town is to answer important ecological questions using cutting edge statistical methods. The case studies below, in which researchers at the centre are involved, illustrate the potential of this exciting field.</p>
<h2>Case studies of statistical ecology in Africa</h2>
<p>The South African <a href="https://www.sanbi.org/biodiversity/building-knowledge/biodiversity-monitoring-assessment/freshwater-programme-birdie-project">Biodiversity Data Pipeline for Wetlands and Waterbirds</a> is a clear example of a project that can make an impact on conservation. This collaborative project led by the <a href="https://www.sanbi.org/">South African National Biodiversity Institute</a> collates data from citizen science bird monitoring programmes to determine the state of waterbird populations and wetlands. Information about population trends and species distribution is critical for conservation managers. The project will transform raw data into usable indicators and display the results online for anyone to see. It has the potential to inform decisions and policies.</p>
<p>Statistical ecology can also help limit poaching. From <a href="https://www.savetherhino.org/rhino-info/poaching-stats/">rhinos</a> and <a href="https://www.nationalgeographic.com/animals/article/wildlife-african-elephants-population-decrease-great-elephant-census">elephants</a> to <a href="https://www.dailymaverick.co.za/article/2021-05-02-the-abalone-connection-the-ties-that-bind-poaching-and-smuggling-with-the-sa-crystal-meth-industry/">abalone</a> and <a href="https://africageographic.com/stories/cycads-are-you-living-next-door-to-a-poacher/">cycads</a>, wildlife trade is a threat to African biodiversity.</p>
<p>A recent study by researchers analysed data collected by rangers to <a href="https://theconversation.com/statistical-models-and-ranger-insights-help-identify-patterns-in-elephant-poaching-137834">identify elephant poaching hotspots</a>. Across the African continent, tens of thousands of wildlife rangers patrol wide areas every day, helping track biodiversity and threats to it. The challenge is that the locations of elephant carcasses they detect may reflect patrol patterns rather than true poaching patterns. The researchers <a href="https://www.sciencedirect.com/science/article/pii/S0006320719319512">used tailored statistical techniques</a> to correct this bias and show where poaching was actually concentrated within their Zimbabwean study site.</p>
<p>Sometimes, researchers need to use refined techniques to gather reliable data, particularly when the species is difficult to detect. For instance, acoustic monitoring was <a href="https://theconversation.com/pasha-53-why-we-listened-to-tiny-frogs-131685">used</a> to keep track of the population of the Cape Peninsula moss frog. Researchers placed microphones at the study sites to record sounds from the environment. Then, they used automated sound recognition software to distinguish calls from the moss frogs. Frog abundance could be estimated from the frequency and location of calls using <a href="http://john.measey.com/aSCR">innovative statistical models</a>. These imaginative procedures allowed them to monitor the population of this threatened endemic species without the need for specialist field staff.</p>
<h2>Challenges and the way forward</h2>
<p>Despite these promising examples, statistical ecology has yet to reach its potential in Africa. <a href="https://www.nature.com/articles/ncomms9221">Large gaps remain</a> in African biodiversity data, linked to limited local research funding and government support in many countries. <a href="https://www.nature.com/articles/d41586-018-07106-5">Citizen science</a> and <a href="https://earthengine.google.com/">remote sensing</a> are exciting options for addressing these limitations at relatively low cost, yet specialised skills are needed to analyse these data.</p>
<p>There is a promising trend of growing research and training in statistical ecology in Africa, but many institutions lack capacity and resources. Researchers from the Global-North working on African systems should try to collaborate <a href="https://conbio.onlinelibrary.wiley.com/doi/pdf/10.1111/csp2.517">more meaningfully</a> with African institutions to help address these gaps. This is critical to enrich the way data informs decisions in African biodiversity management and policy.</p>
<p>There’s a unique opportunity next year to share knowledge, build capacity, and create a long-term collaboration network. Our centre in Cape Town is hosting the <a href="https://www.isec2022.org/">International Statistical Ecology Conference</a>, a flagship event in the field. We encourage Africans working in this space to <a href="https://www.isec2022.org/">submit an abstract</a>.</p><img src="https://counter.theconversation.com/content/171513/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Henintsoa Onivola Minoarivelo is based at the Centre for Statistics in Ecology, Environment and Conservation, within the department of Statistical Sciences at the University of cape Town. She receives funding from the DAAD ClimapAfrica programme. </span></em></p><p class="fine-print"><em><span>Francisco Cervantes Peralta is a post-doctoral researcher at the Centre for Statistics in Ecology, Environment and Conservation (University of Cape Town), and at the South African National Biodiversity Institute. His position is funded by the JRS Biodiversity Foundation.</span></em></p><p class="fine-print"><em><span>
Timothy kuiper is currently a Postdoctoral Research Fellow at the Centre for Statistics in Ecology, Environment and Conservation at the University of Cape Town (UCT). He receives funding from the National Research Foundation (South Africa) and the University Research Council at UCT. </span></em></p>There is a promising trend of growing research and training in statistical ecology in Africa.Henintsoa Onivola Minoarivelo, Postdoctoral research fellow, University of Cape TownFrancisco Cervantes Peralta, Post-doctoral Researcher in Statistical Ecology, University of Cape TownTimothy Kuiper, Postdoctoral Research Fellow, University of Cape TownLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/960862018-07-13T10:24:32Z2018-07-13T10:24:32ZScientist at work: Identifying individual gray wolves by their howls<figure><img src="https://images.theconversation.com/files/227222/original/file-20180711-27015-1dr73z1.jpg?ixlib=rb-1.1.0&rect=164%2C226%2C2079%2C1483&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Each wolf calls with its own 'voice.'</span> <span class="attribution"><span class="source">Angela Dassow</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Love them or hate them, wolves are vital members of natural ecosystems and the health of a wolf population can be an important factor in <a href="https://www.livingwithwolves.org/about-wolves/why-wolves-matter/">maintaining balance</a> among species. Wolf populations are growing in North America – the Great Lakes region in particular now supports over <a href="https://www.fws.gov/midwest/wolf/aboutwolves/wolfpopus.htm">3,700 individuals</a>. Keeping track of wolf pack movements is important for reducing human-wolf conflicts which can arise when packs move too close to ranches.</p>
<p>The traditional way to track wolves involves setting traps, sedating and then radio-collaring individual animals. While effective, this approach is time intensive and expensive, and entails risks for the animals. </p>
<p>I was fortunate to participate in this entire process firsthand as an undergraduate student. During the summer trapping seasons, I became familiar with each of the wolves in the central forest region of Wisconsin. This experience led to several conversations with the wildlife biologists in the area about whether wolf howls could be used to help identifying non-radio-collared pack members.</p>
<p><audio preload="metadata" controls="controls" data-duration="5" data-image="" data-title="Howl from a wild adult wolf, recorded in central Wisconsin by author Angela Dassow and Carthage College biology students, Cara Hull and Caitlin McCombe." data-size="119400" data-source="" data-source-url="" data-license="Author provided" data-license-url="">
<source src="https://cdn.theconversation.com/audio/1199/south-bluff-filtered-howl.mp3" type="audio/mpeg">
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<div class="audio-player-caption">
Howl from a wild adult wolf, recorded in central Wisconsin by author Angela Dassow and Carthage College biology students, Cara Hull and Caitlin McCombe.
<span class="attribution"><span class="license">Author provided</span><span class="download"><span>117 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/1199/south-bluff-filtered-howl.mp3">(download)</a></span></span>
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<p>This question remained a fun thought experiment for many years. Now <a href="https://www.carthage.edu/live/profiles/1488-angela-dassow">as a biology professor</a> who specializes in <a href="http://ocr.org/learn/bioacoustics/">bioacoustics</a>, I’ve been able to turn that thought experiment into a full research question: Can we use acoustic features to identify individual wolves in the wild? </p>
<h2>Downsides of radio collaring</h2>
<p>Because of the many challenges involved in radio collaring an animal, it would be useful to have a new way to identify and track wild wolves.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=568&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=568&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=568&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=714&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=714&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227472/original/file-20180712-27024-1pztro3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=714&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 U.S. Fish and Wildlife Service employee fastens a radio collar onto a sedated female gray wolf.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/usfwsmtnprairie/8488974469">Lori Iverson/USFWS</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>To successfully set a trap, wildlife managers must first spend days, if not weeks, scouting for signs of wolves. Once they’ve identified a suitable area, they set traps that must be checked every 24 hours. If successful, the animal needs to be sedated before it can be removed from the trap – which can be stressful both for the wolf and the researchers involved.</p>
<p>A sedated wolf cannot regulate its body temperature and overheating can become an issue on hot days. Human handling of a sedated wolf can also be stressful on the pack members that are often nearby, observing the scene. Even after an animal is successfully radio-collared and released, it’s still vulnerable to predators while the sedative wears off.</p>
<p>In spite of these risks, radio-collaring has been the standard way to track populations because each collar’s radio-transmitter frequency acts as a unique identifier of an individual. Researchers can then use aerial surveys where a pilot searches for the collared animal or ground surveys where a field crew drives throughout a pack territory searching for feedback from the radio signal. This method is used to track a wide array of animals, including turtles, birds, bats, whales, fish, snakes and more.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/223229/original/file-20180614-32319-1juwm5r.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Angela Dassow and Cara Hull survey a road in central Wisconsin for signs of wolves.</span>
<span class="attribution"><span class="source">Caitlin McCombe</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Listening to learn who’s who</h2>
<p>In 2013, behavioral ecologist <a href="https://scholar.google.com/citations?user=CZyS1lMAAAAJ&hl=en&oi=sra">Holly Root-Gutteridge</a> and her colleagues successfully demonstrated that they could <a href="https://doi.org/10.1080/09524622.2013.817318">identify individual wolves in captivity using acoustic features</a>. Their research provided evidence that it made sense to test whether vocal identification in wild animals is possible.</p>
<p>So with the support of the <a href="https://www.carthage.edu/sure/">Summer Undergraduate Research Experience</a> at <a href="https://www.carthage.edu/">Carthage College</a>, volunteers from the <a href="http://www.timberwolfinformation.org/">Timber Wolf Information Network</a>, and wildlife managers at <a href="https://dnr.wi.gov/topic/lands/wildlifeareas/sandhill/">Sandhill Wildlife Area</a> in Babcock, Wisconsin, my undergraduate students Cara Hull and Caitlin McCombe and I began to record wolves in the wild.</p>
<p>It would be an understatement to say fieldwork can be challenging. On any given day, there can be daunting weather fluctuations. Biting insects, especially mosquitoes and deer flies, are abundant in wolf habitat. We had to constantly check ourselves for ticks. And then of course comes the actual fieldwork. </p>
<p>Wolves naturally avoid coming near people, but the best quality recordings are made up close to where the animals are producing the sounds. To get close with our audio equipment, we had to track the wolves every day to learn where they’d most recently been within their large territories. That’s how we’d establish a starting point for our nightly recording sessions.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=765&fit=crop&dpr=1 600w, https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=765&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=765&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=962&fit=crop&dpr=1 754w, https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=962&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/223228/original/file-20180614-32304-mgakkr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=962&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fresh track from an adult gray wolf.</span>
<span class="attribution"><span class="source">Angela Dassow</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Conducting a daily survey of wolf habitat requires driving or walking down every possible path within a wolf’s territory. Signs of activity could include fresh footprints or tracks. This can tell us how many animals were in the area and what direction they were heading.</p>
<p>Large dogs can produce footprints that are similar in size to those of wolves; but the pattern of tracks can be distinguished based on the placement of their feet and the directness of the chosen route. Dogs have a tendency to wander more, while wolves will walk in a more efficient straight line.</p>
<p>In addition to tracks, we conduct a survey of fresh scat. It’s not glamorous, but examining their feces provides valuable information about what the wolves have been eating and how recently they walked along a trail.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/223050/original/file-20180613-32323-8i1dwh.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">Carthage College biology students Cara Hull and Caitlin McCombe conduct a howl survey in central Wisconsin.</span>
<span class="attribution"><span class="source">Angela Dassow</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Using the information from our daytime survey, we plan a shorter nighttime howling route. Howling is a natural behavior during the evenings, when wolves call to signal that a territory is occupied. At each stopping point on our route, a researcher must get out of the vehicle and howl while another researcher records with a microphone any wolf responses, announcing their presence or defending territory. If we are successful in eliciting a response, we continue in its direction until we get as close as possible.</p>
<p>Use of lights is discouraged since it can deter the wolves from calling again, so we needed to feel our way through the forest at night. Personally, I think it is incredibly exciting to be walking down a trail in the dark and have a wolf walk within feet of where I am. It may sound scary, but we are not in any danger since wolves prefer to avoid contact with humans. During our month-long survey, we were fortunate to experience two close wolf encounters. </p>
<h2>Back in the lab, analyzing the calls</h2>
<p>With the howls recorded, we can return to the lab to analyze our findings using audio software.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/223230/original/file-20180614-32316-16wyrn2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Acoustic properties are measured using Adobe Audition.</span>
<span class="attribution"><span class="source">Angela Dassow</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We were able to isolate 21 howls from two adult wolves over two evenings. For each howl, we made six types of frequency measurements and two types of duration measurements. Frequency is how high or low the pitch of the howl sounds and duration is the length of time the howl lasted.</p>
<p>For wild gray wolves, we found that the maximum frequency – that is, the highest sound an animal produced – and the frequency at the end of the howl were the two variables that were most individualistic. For captive wolves, it was different. The lowest frequency an individual produced – what in acoustics is called their fundamental frequency – and the loudness of its calls were the factors that best differentiated among the captive individuals.</p>
<p>The differences in useful identification information between wild and captive howls are likely a reflection of signal quality. The captive recordings are much clearer than what we were able to record in the wild, where we were typically at least half a mile away from the wolves; the signal degrades with distance. As signal quality declines, maximum frequency and end frequency become more useful in individual identification.</p>
<p>Based on our findings and previous research, it is possible to monitor gray wolf populations using non-invasive methods. To do so effectively, researchers would need to record known individuals in a particular area. Once they’ve built up a database of known individuals’ howls, they can conduct nightly surveys. Comparing new recordings to those in the audio library would let them determine which individuals are in an area. </p>
<p>While radio-collaring procedures may still be useful in some cases, vocal identification is a promising alternative for monitoring individuals. Acoustic surveys are still a time-consuming process, but they eliminate the time needed to trap individuals and remove any possibility of accidentally injuring an animal in a trap. Additionally, once researchers gather a database of positively identified individuals, they can use remote monitoring stations to record howls, thus reducing the amount of time spent conducting nightly surveys. Acoustic monitoring could potentially track all the wolves in multiple packs whereas radio-collaring is typically used to track a single member in select packs.</p><img src="https://counter.theconversation.com/content/96086/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Angela Dassow does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Tracking wild animals can provide lots of valuable data. New research suggests audio recordings of wild wolves can replace the typical radio collars, which can be expensive and intrusive.Angela Dassow, Assistant Professor of Biology, Carthage CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/699142016-12-11T06:18:04Z2016-12-11T06:18:04ZHow we learned to listen to elusive, threatened frogs<figure><img src="https://images.theconversation.com/files/148908/original/image-20161206-25738-16zp2hx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Cape peninsula moss frog is smaller than 20mm and is, therefore, hard to monitor.</span> <span class="attribution"><span class="source">Francois Becker</span></span></figcaption></figure><p>Scientists the world over have a frog problem: we have little idea of how many frogs there are in each species in the world. This means that we are unable to predict how many there will be in the future due, for example, to the effects of climate change.</p>
<p>There have been very few studies recording the size of amphibian populations. So those of us studying amphibians have very little with which to work. What we do know is that many frogs are under threat mostly from habitat change, but also from disease. In southern Africa they are particularly vulnerable to <a href="http://john.measey.com/media/545057e1-8025-4abd-9aa7-3a90f470dd01/NgmUbw/PDFs/Measey_2011_Ensuring.pdf">invasive species</a>.</p>
<p>Male frogs advertise their presence with species specific mating calls. Determining their presence has traditionally entailed listening for these calls. If you want to know how many frogs are calling, then stand with your hands behind your ears and try to count all the animals you hear. It sounds simple, but it’s not that easy. I’ve tried. </p>
<p>Listening to 10 calling animals is taxing. More than 10 and it’s possible to get muddled. Choruses of over 50 sound like noise. </p>
<p>Luckily the revolution in digital media has helped those of us studying amphibians. We’re able to monitor vocalising species and record a large number of sounds from the environment. Automated computer software, like voice recognition on smart phones, can then pick out particular species from their calls. Acoustic monitoring is ideal for monitoring the abundance of a species over time, as it has minimal impact on the species being monitored. </p>
<p>But what then? Interpreting the number of calls is problematic for several reasons. First and foremost is the fact that the area a microphone listens to is not defined. The vagaries of the acoustic environment mean that the slightest wind, or even a change in humidity, can affect the distance over which sound propagates. This means that microphones listen to different areas every time they record.</p>
<p>Recently <a href="http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12810/full">published research</a> by my colleagues and I could change this. It provides a methodology for acoustic monitoring that calculates the area listened to by an array of microphones, as well as estimating the number of calls made in that area. This has important implications for acoustic monitoring – and for attempts to catalogue just how many frogs are “ribbiting” around us. </p>
<h2>A new methodology</h2>
<p>We used microphones to monitor the Cape peninsula moss frog (<em>Arthroleptella lightfooti</em>) in Table Mountain National Park, South Africa. These frogs are endemic to the area and occur nowhere else on the planet. They are listed as “<a href="http://www.iucnredlist.org/details/58061/0">Near Threatened</a>” on the IUCN list of threatened species. Any data we can glean will contribute to their conservation. </p>
<p>We used an array of six microphones to monitor populations of Cape peninsula moss frogs over their winter breeding season from May to October. </p>
<p>Researchers have previously used time of arrival of sound at each microphone in an array to determine the position <a href="https://youtu.be/JTYFYtZJXro">of calling animals</a>. </p>
<p>We used a novel statistical technique developed by co-author statisticians Stevenson and Borchers (<a href="http://john.measey.com/ascr">Spatial Capture Recapture: SCR</a>) to analyse the automated call data. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/148901/original/image-20161206-25721-ysekwe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Listening for calls of the endangered Arthroleptella subvoce to monitor its abundance in the Groot Winterhoek Wilderness Area, South Africa.</span>
<span class="attribution"><span class="source">John Measey</span></span>
</figcaption>
</figure>
<p>The analysis takes into account both microphones which hear calls and those which don’t hear calls, as well as the distance between microphones to build up an estimate of the number of calls and the <a href="https://youtu.be/JTYFYtZJXro">area from which the calls come</a>. For an encore, the statisticians combined the information from time of arrival and call amplitude difference with Spatial Capture Recapture to build the first ever statistical estimate of the density of calling male frogs from an acoustic array.</p>
<p>We also recorded rainfall and temperature and were surprised to find that the number of frogs calling at each site didn’t relate to either of these factors. Instead, it started off with relatively few animals calling early in the season (May), built to a fine crescendo in July and then tailed off toward October.</p>
<p>More surprising was that the area in which the microphone array could detect frog calls nearly doubled (from 400 to 800 m₂) during the winter breeding season. But because the technique accounted for this change in the size of the sampling area we could effectively monitor the calling density of the species without having to worry about the changing areas that the microphones recorded.</p>
<h2>The new direction</h2>
<p>The idea of using an array of microphones is not new. Using the time of arrival of sounds to each microphone to determine the presence of a calling animal, such as a frog, is old hat. The technique we’ve <a href="http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12810/full">pioneered</a> provides a new direction for acoustic monitoring because we were able to define the area in which the microphone array was detecting calls. </p>
<p>The study has produced a robust technique for estimating call density. This is because it combined the statistical wizardry that allowed estimates from Spatial Capture Recapture with the time of arrival and signal strength. That combination makes it possible to increase the accuracy of the estimate of call density.</p>
<p>Researchers wishing to take advantage of the wonders of digital media to monitor species at risk of climate change, <a href="https://theconversation.com/the-future-for-frogs-looks-bleak-unless-humans-change-their-habits-57505">like frogs</a>, can now use a technique that will give them call density which can be compared across recording occasions. </p>
<p>This will contribute to our understanding of how threatened species which vocalise are faring on our changing planet.</p><img src="https://counter.theconversation.com/content/69914/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Measey receives funding from National Geographic, the Centre for Invasion Biology (CIB), and the National Research Foundation (NRF). </span></em></p>A robust technique using the wonders of digital media has helped researchers understand how threatened species like frogs are faring on our globally changing planet.John Measey, Senior Researcher at the CIB based in the Department of Botany and Zoology, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/523392015-12-17T09:53:51Z2015-12-17T09:53:51ZHow noise pollution is changing animal behaviour<figure><img src="https://images.theconversation.com/files/106033/original/image-20151215-23198-1au0gnp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Urban noise pushes birds to sing in high pitch and ship sound deafens whales and dolphins.</span> <span class="attribution"><a class="source" href="http://linkbun.ch/03wvq">John Haslam, Eric Bégin, IK's World Trip, Green Fire Productions, flickker photos, Jay Ebberly / Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Noise pollution, generally an unintended byproduct of urbanisation, transport and industry, is a key characteristic of human development and population growth. In some cases, it is produced intentionally, for example when seismic surveys are being carried out using powerful airgun arrays to explore and map the seafloor, or active sonar, which uses sound waves to detect objects in the ocean. </p>
<p>All of this noise – whether intentional or not – has the ability to alter the acoustic environment of aquatic and terrestrial habitats. This can have a dramatic effect on the animals that live in them, perhaps even driving evolutionary change as species adapt to or avoid noisy environments.</p>
<h2>Rising noise levels</h2>
<p>The dramatic and comparatively recent rise in noise levels is marked in both magnitude and extent, with an estimated <a href="http://www.euro.who.int/en/health-topics/environment-and-health/noise/data-and-statistics">30% of the European population</a> exposed to road traffic noise levels greater than 55dB (decibels) at night, well above <a href="http://www.euro.who.int/en/health-topics/environment-and-health/noise/policy/who-night-noise-guidelines-for-europe">the 40dB target recommended by the World Health Organisation</a>. Even remote natural areas do not escape the reach of anthropogenic, or manmade, noise. One study <a href="http://link.springer.com/article/10.1007/s10980-011-9643-x">across 22 US national parks</a> demonstrated that this kind of noise was, on average, audible more than 28% of the time.</p>
<p>Noise is not just irritating; we have known for some time that <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1253729/">it can have direct human health impacts</a>. Indeed, chronic exposure to noise levels above 55dB dramatically increases the risks of heart disease and stroke, while aircraft noise <a href="http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=70319&fileId=S0033291701003282">has been shown</a> to impact the development of reading skills in children attending schools close to busy airports. <a href="http://www.euro.who.int/__data/assets/pdf_file/0008/136466/e94888.pdf">The WHO estimates</a> that in Europe at least a million healthy life years are lost every year due to traffic noise.</p>
<h2>Changing behaviours</h2>
<p>But what are the implications for wildlife, particularly given how important sound production and hearing are for a range of behaviours, such as locating food, avoiding predators and finding a mate? For example, bats and dolphins rely on high frequency sonar to detect highly mobile prey, while great tits, red deer and grasshoppers are among the many species that advertise their dominance and desirability using vocalisations. Elephants <a href="http://www.nature.com/news/elephants-recognize-the-voices-of-their-enemies-1.14846">can even use sound</a> to determine the threat presented by different human groups. </p>
<p>Scientific interest in the effects of noise pollution on wildlife has intensified over the past decade and we are now developing a better understanding of how noise can impact behaviour, population and community level processes <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12207/abstract">across a range of animal species</a>. Using experimental and observational approaches to characterise and explore the specific effects of different noise sources, the evidence generated from these studies is considerable, particularly among songbirds and marine mammals, which rely heavily on sound and vocal communication. </p>
<p>We now know, for example, that the foraging, vocal behaviour and physiological stress of cetaceans – whales, dolphins and porpoises – can be <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12207/abstract">impacted by ship noise</a>. This is of particular concern for species such as the endangered <a href="http://rsbl.royalsocietypublishing.org/content/7/1/33.short">North Atlantic right whale</a> that inhabits coastal US waters that experience very high levels of shipping traffic. Furthermore, in addition to shifts in distribution and vocal behaviour, military sonar has also been linked <a href="http://www.livescience.com/44598-new-whale-stranding-from-sonar.html">to the stranding of cetaceans</a>. </p>
<p>The impacts are not just limited to marine mammals, considerable negative effects of noise are also documented in marine and freshwater fish and invertebrates. These include recent studies that have demonstrated compromised <a href="http://www.sciencedirect.com/science/article/pii/S0003347213001991">anti-predator behaviour in crabs</a> and eels exposed to ship noise.</p>
<p>In terrestrial habitats, bird diversity and abundance has been shown to decline as a result of chronic noise levels <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12207/abstract">around cities and along roadways</a>. A number of species have demonstrated adjustments to their vocal behaviour in an attempt to adapt to the cacophony of human noise. Urban great tits for example, are able to <a href="http://www.nature.com/nature/journal/v424/n6946/full/424267a.html">raise the frequency of their calls</a> to reduce acoustical masking by predominantly low-frequency urban noise, while European robins adjust <a href="http://rsbl.royalsocietypublishing.org/content/3/4/368">the timing of their singing</a> to coincide with quieter periods in the city. Meanwhile, black-chinned hummingbirds and house finches appear to actively select noisy areas <a href="http://www.sciencedirect.com/science/article/pii/S0960982209013281">near active gas wells</a> to avoid nest predation by more disturbance sensitive species.</p>
<p>Roads are a major source of terrestrial noise due to their spatial extent and the volume of traffic. A <a href="http://bit.ly/2247Jgl">2003 study</a> calculated that 83% of the lower 48 states of the US was within about 1km of a road. I have been working with colleagues at Colorado State University and the National Park Service to explore the effects of road noise on the prairie dog, a social mammal. </p>
<p>Our research demonstrated that prairie dogs, which commonly live in habitats near roads and urban areas, significantly reduced their foraging and increased their vigilance behaviour <a href="http://www.sciencedirect.com/science/article/pii/S0003347214002486">when exposed to road noise</a>. Such shifts in behaviour could have impacts on their long-term population health particularly in combination with other stressors such as disease and habitat loss. </p>
<p>Road noise <a href="http://onlinelibrary.wiley.com/doi/10.1111/gcb.12997/full">has also been shown</a> to impair the foraging efficiency of bats <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12207/abstract">and alter vocal communication</a> in frogs and invertebrates.</p>
<h2>Difficulties of measurement</h2>
<p>Studying noise isn’t an easy thing to do. First of all, sound levels cannot accurately be measured and defined using a single absolute scale, such as those used for temperature, rainfall and wind speed. For simplicity we often just refer to a decibel level, but this does not take into account the duration and frequency of the acoustical signal. The specific effects of noise also need to be disentangled from the sources of disturbance that often accompany it, including human presence, habitat fragmentation and chemical pollution. </p>
<p>The need to further understand the complex biological effects of noise and establish scientifically relevant thresholds of noise exposure is a priority for human health and wildlife conservation. Rapid development, urbanisation and population growth are set to continue into the future. As a result we need to ensure a collaborative effort between scientists, industry and government to protect natural soundscapes where possible, while also promoting new technology and approaches that mitigate the effects of noise.</p>
<p>Man made noise is a relatively recent phenomenon, particularly in evolutionary terms, but scientific studies have demonstrated that it has the potential to adjust behaviour, alter physiology and even restructure animal communities. Ultimately, such a strong selection pressure could <a href="http://bit.ly/1SZgHFI">drive evolutionary change</a>. These are complex questions that are now being explored by experts across a range of disciplines from animal behaviour to bioacoustics.</p><img src="https://counter.theconversation.com/content/52339/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Graeme Shannon received funding from the US National Park Service. </span></em></p>Noise pollution, whether on land or under water, can affect animals in interesting – and not always positive – ways.Graeme Shannon, Lecturer, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/423842015-06-11T05:13:44Z2015-06-11T05:13:44ZEvery citizen scientist will soon have the tools of a specialist<figure><img src="https://images.theconversation.com/files/84561/original/image-20150610-6804-1w6534o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spring watchers</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Ordinary citizens have become increasingly important to scientific research over the past decade. Today, mobile phone technologies, relatively cheap cameras and almost ubiquitous internet connectivity have opened up new opportunities for conservation organisations to engage with ordinary citizens and encourage citizen science. </p>
<p>A citizen scientist is a volunteer who collects and/or processes data as part of a scientific enquiry. This could mean noting the plants found on a day trip or more systematically recording wildlife in a special area. While citizen science projects can be in any branch of science, my focus is on wildlife research.</p>
<p>The list of citizen science projects is long. This year’s <a href="http://www.bbc.co.uk/blogs/natureuk/entries/ec03f10b-aa7e-46a4-8671-67d8f9069bec">BBC Springwatch</a>, which concludes this week, has highlighted a number of mass participation projects in which people can become involved, such as recording the first signs of spring. All such schemes are predicated on the idea that people will go out and report what they see.</p>
<p>But technological advances are also changing the way that professional scientists collect and record data on animals. These changes often require specialised equipment and resources beyond the scope of most amateurs. Now that new technologies are changing the working practices of professional ecologists, what does this mean for citizen science?</p>
<h2>DNA testing</h2>
<p>Until recently, the way to ascertain the presence of great crested newts in a pond was to go and look. Because the newt is a protected species, disturbing it is illegal. But just looking for the adults or their eggs is not. Today, however, finding great crested newts and other aquatic animals can be done using <a href="http://www.freshwaterhabitats.org.uk/projects/edna/">environmental DNA</a> (eDNA).</p>
<p>DNA is released into the water by plants and animals in a host of ways: from their skin, faeces, mucous, hair, eggs and sperm, or when they die. By simply collecting and analysing a water sample from the pond or stream, we can find traces of eDNA and identify the animals living there, even if they are hard to recognise. </p>
<p><a href="http://www.barcodeoflife.org/content/about/what-dna-barcoding">DNA barcoding</a> allows species to be identified using short genetic markers in an organism’s DNA. And actually, these barcodes can be obtained from tiny amounts of tissue even by non-specialists. All that is required is the correct DNA processing and sequencing technology. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/84562/original/image-20150610-6798-g7o973.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">New tools of the trade.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Genetic identification is not the only way in which technological advancement is changing the way that we record the species around us. Noting the birds in a woodland is more often than not a case of listening and identifying the songs rather than seeing the birds themselves.</p>
<p>Eco-acoustics or <a href="http://link.springer.com/article/10.1007%2Fs10980-011-9600-8">soundscape ecology</a> studies the relationships between animals and their environment based on sound. There are now technologies available that allow birds and amphibian communities to be identified <a href="http://www.bioone.org/doi/abs/10.2193/0091-7648%282006%2934%5B211%3AUADRSA%5D2.0.CO%3B2?journalCode=wbul">from sound recordings</a>.</p>
<p>This means that it will soon be possible to place an audio recorder in the field and walk away while it records birdsong and other sounds over an extended period of time. The aim is that the recordings can be analysed automatically using software to draw up a species list for that area.</p>
<h2>Raising standards</h2>
<p>But if the collection of wildlife data is to reveal useful information, it needs to be done systematically. Recording the presence of a wildlife species only tells you that it was there at the time that it was recorded. To spot trends, the recording needs to be repeated in the same way over a number of years.</p>
<p>This can be difficult when relying on volunteers, but it is not impossible and there are many good examples of systematic surveys, but these are mainly carried out by people with a little more than basic knowledge.</p>
<p>In fact, technology is now progressing to the point that it can do the work of a specialist on behalf of any citizen, helping to standardise measurements and carry out complex analysis instead of just simple observations. For example, <a href="http://newforestcicada.info">a new app</a> enables visitors to the New Forest to search for cicadas - last sighted in the forest in 2000 - by analysing sound recordings of background noise captured with a mobile phone. It’s not hard to imagine similar projects asking people to collect and study samples of eDNA or make regular recordings of the dawn chorus using easily available tools.</p>
<p>Mass recording of wildlife sightings such as those requested by the BBC and <a href="http://www.mammal.org.uk/have-you-seen-easter-bunny">the Mammal Society</a> are not simply about recording wildlife for scientific enquiry. They are about individuals, couples and families going outside, exploring and connecting with their environment. Discovering what is there and being part of a larger group of people. It is about making new discoveries together. </p>
<p>But with new technologies, the details of citizen science will change. Future technological advances will present new ways to continue our long established heritage of amateur natural history.</p><img src="https://counter.theconversation.com/content/42384/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip James 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>Rapid changes in technology are transforming the contributions ordinary citizens can make to scientific research.Philip James, Professor of ecology, University of SalfordLicensed as Creative Commons – attribution, no derivatives.