tag:theconversation.com,2011:/global/topics/whale-23470/articleswhale – The Conversation2023-12-06T14:57:34Ztag:theconversation.com,2011:article/2192452023-12-06T14:57:34Z2023-12-06T14:57:34ZWhy we need a moratorium on eel fishing<figure><img src="https://images.theconversation.com/files/563600/original/file-20231204-29-8fvv83.jpg?ixlib=rb-1.1.0&rect=194%2C85%2C4718%2C3282&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/es/image-photo/european-eel-anguilla-species-snakelike-catadromous-1569398527">Martin Pelanek/Shutterstock</a></span></figcaption></figure><p>All 19 species of Anguillid eels <a href="https://www.thamesriverstrust.org.uk/thames-catchment-community-eels-project/life-cycle-of-an-eel/">migrate</a> from the sea, where they are born, to the freshwater systems in which they grow. After a period of up to 20 years, they reach maturity and return to the sea to breed and die. </p>
<p>These migrations have lent the eel a certain air of mystery over the years, but this has not prevented them from ending up on dinner plates across the world. </p>
<p>All cultures with access to eels have eaten them, and eel remains are frequently found in <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379108000735">paleolithic archaeological sites</a>. Indeed, some might even argue that eels, not turkey, should be the symbol of American thanksgiving: when the exhausted crew of the Mayflower celebrated the first American thanksgiving, <a href="https://www.themarginalian.org/2022/11/20/eel-squanto-thanksgiving/">much of what they ate was eels</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=137&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=137&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=137&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=172&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=172&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563308/original/file-20231204-21-qdib1o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=172&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">American eel (<em>Anguilla rostrata</em>)</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Anguillarostratakils.jpg">Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p><a href="https://en.wikipedia.org/wiki/Eel_as_food">Contemporary cuisine</a> finds multiple uses for the fish, from smoked European variants to Korean <em>Jangeo-gui</em> and the Valencian dish <em>all i pebre</em>. They are a common ingredient in many parts of the world. However, the <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/fme.12302">industrialisation and globalisation of eel consumption</a> has caused their numbers to collapse.</p>
<p>A moratorium on eel fishing is needed.</p>
<h2>Whaling ban: a template for action on eels</h2>
<p>Almost <a href="https://www.scientificamerican.com/article/world-s-whaling-slaughter-tallied-at-3-million/">three million</a> large cetaceans were hunted over the course of the 20th century. Faced with the evident decline of whale populations, the <a href="https://iwc.int/en/">International Whaling Commission</a> was set up in 1946, with the mission of guaranteeing “the proper conservation of whale stocks and (…) the orderly development of the whaling industry”. Over the years it became clear that this mission had failed, as whale populations could not withstand the pressure they were under due to hunting. A total cessation of whaling activity was needed.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=475&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=475&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=475&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=597&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=597&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563309/original/file-20231204-23-pf57ir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=597&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Evolution of catches of 4 of the species most heavily targeted by the 20th century whaling industry: blue whale (<em>Balaenoptera musculus</em>), fin whale (<em>Balaenoptera physalus</em>), Sei whale (<em>Balaenoptera borealis</em>) and sperm whale (<em>Physeter macrocephalus</em>). The last is depicted here.</span>
<span class="attribution"><span class="source">Author's own, adapted from https://ourworldindata.org/grapher/whale-catch</span></span>
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<p>After several unsuccessful attempts, <a href="https://todayinconservation.com/2020/03/july-23-commercial-whaling-banned-1982/">a moratorium</a> on whaling was agreed in 1982, and has been in place since 1986. The role of countries without a whaling industry (such as Mongolia, Austria or Mali), as well as the support of countries that did hunt whales, among them Spain, was fundamental to reach the majority required.</p>
<p>Only <a href="https://elpais.com/diario/1982/05/10/sociedad/389829601_850215.html">two months before the vote</a>, Spain opposed the moratorium because it claimed to have “absolute and truly exemplary control over whaling”. However, its last minute change of vote ended up being decisive in the ban’s approval. </p>
<p>Despite the vote, Spain maintained its whaling activity up to the limit of what was permitted. The <a href="https://www.rtve.es/play/videos/te-acuerdas/acuerdas-hace-25-anos-se-prohibio-caza-ballenas-fines-comerciales/772189/">Spanish whaling industry</a> made its last catch in <a href="https://www.xataka.com/magnet/historia-ultima-ballena-cazada-espana-1985-auge-caida-industria-ancestral">October 1985</a>, when a fin whale was killed off the coast of Galicia.</p>
<p>The whaling moratorium undoubtedly has weaknesses, but it is a <a href="https://www.nature.com/articles/s41598-022-13798-7">collective success</a> for humanity. Taking it as an example, <a href="https://www.bbc.com/news/science-environment-61167925">David Attenborough</a> has said that “we know what the problems are and we know how to solve them. All we lack is unified action.”</p>
<p>This is exactly what needs to be done for eels.</p>
<h2>Heading towards an eel fishing ban</h2>
<p>The most heavily <a href="https://springerplus.springeropen.com/articles/10.1186/2193-1801-3-534">overfished and threatened</a> eel species are the European (<em>A. Anguilla</em>), Japanese (<em>A. japonica</em>) and American (<em>A. rostrata</em>). No fewer than 20 years ago, the <a href="https://www.researchgate.net/publication/40800861_Worldwide_decline_of_eel_resources_necessitates_immediate_action_Quebec_Declaration_of_Concern#fullTextFileContent">Quebec Declaration of Concern</a> made an urgent appeal for the protection of these fish. <a href="https://afspubs.onlinelibrary.wiley.com/doi/full/10.1080/03632415.2014.979342">Ten years later</a> the situation had not improved at all, and it remains the same today. <a href="https://www.science.org/doi/10.1126/science.abj3359">Continued exploitation will prevent any possible recovery</a> and will ultimately lead to their extinction.</p>
<p>An international moratorium like the whaling ban is the most effective way to conserve eel populations, but it is complex. Coordinated international action is essential to address the overexploitation of multiple species which are distributed across many countries and traded internationally. </p>
<p>The moratorium should involve a total ban on eel fishing for a reasonable period (at least a decade) and a total ban on the marketing of eel products in any form.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=528&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=528&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=528&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=664&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=664&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563311/original/file-20231204-19-9zmues.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=664&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Evolution from 1960 to 2000 of an index of young populations of the three most exploited and threatened eel species: Japanese (<em>Anguilla japonica</em>), European (<em>Anguilla anguilla</em>) and American (<em>Anguilla rostrata</em>). The map above shows their geographic distribution.</span>
</figcaption>
</figure>
<p>The global popularity of Japanese cuisine, <a href="https://www.traffic.org/site/assets/files/2482/eel_market_dynamics_report.pdf">which accounts for most of the world’s use of eel</a>, means that the moratorium must apply to eels in general, not just specific species. Eels (known as <em>unagi</em>) are a ubiquitous item on menus in Japanese restaurants around the world. This massive use of eel is the driving force behind its illegal trade, which is <a href="https://freshwaterblog.net/2019/07/05/illegal-trafficking-of-the-european-eel-the-worlds-greatest-wildlife-crime/">the world’s largest wildlife crime</a> and affects <a href="https://www.sciencedirect.com/science/article/pii/S0956713523001524">multiple species</a>. </p>
<p>Nevertheless, problems with eel are not limited to law breaking, or to Japanese restaurants. Large quantities of eel are still legally eaten throughout Europe, and its consumption is promoted at <a href="https://theconversation.com/eels-have-fascinated-us-for-ages-now-we-need-to-stop-eating-them-201520">various gastronomic festivals</a>. </p>
<p>In Spain, glass eels, known as <em>angula</em>, once plentiful and cheap, have become increasingly scarce and expensive. This has led to them becoming <a href="https://www.eleconomista.es/status/noticias/8764552/11/17/Angulas-un-manjar-de-lujo-que-apuesta-por-los-paladares-mas-sibaritas.html">a status symbol</a>, leading in turn to greater intensity of exploitation, more scarcity, and even higher prices. This generates an <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0040415">extinction vortex</a> which, left unchecked, will lead to extinction.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=349&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=349&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=349&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=438&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=438&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563312/original/file-20231204-29-8gh94g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=438&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 European eel in a river in Girona, Spain. Autor: Lluís Zamora.</span>
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</figure>
<h2>Reaching a moratorium</h2>
<p>Coordinating international conservation action is not easy, but the whaling moratorium shows that it is possible. Decisions taken at regional or state level are important because they can be scaled up to build global agreements.</p>
<p>In the case of the European eel, the fishing limitations established by the <a href="https://www.consilium.europa.eu/en/council-eu/configurations/agrifish/">European Union’s Agriculture and Fisheries Council</a> are crucial. These decisions are supposed to follow the recommendations of the <a href="https://www.ices.dk/Pages/default.aspx">International Council for the Exploration of the Sea</a>. However, recommendations to <a href="https://www.ices.dk/community/groups/pages/wgeel.aspx">ban hunting the species</a> have been made for more than 20 years, and have yet to be heeded. As was the case in the International Whaling Commission, the countries, regions and lobby groups that commercially benefit from eel fishing have manoeuvred carefully to maintain the activity.</p>
<p>Europe has a new opportunity to heed the advice of experts and implement a ban, and Spain in particular has the opportunity to change its role and move towards defending the conservation of eels, as it did with whales. Collectively, we have the opportunity to build towards a global ban on eel fishing.</p><img src="https://counter.theconversation.com/content/219245/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Miguel Clavero Pineda no recibe salario, ni ejerce labores de consultoría, ni posee acciones, ni recibe financiación de ninguna compañía u organización que pueda obtener beneficio de este artículo, y ha declarado carecer de vínculos relevantes más allá del cargo académico citado.</span></em></p>High demand for eels around the world has led to massive overfishing and plummeting populations.Miguel Clavero Pineda, Científico titular CSIC, Estación Biológica de Doñana (EBD-CSIC)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1847182022-07-13T16:31:25Z2022-07-13T16:31:25ZBanned flame retardants continue to accumulate in the St. Lawrence River and the whales and fish that live there<figure><img src="https://images.theconversation.com/files/473691/original/file-20220712-32020-gd8qg5.jpg?ixlib=rb-1.1.0&rect=14%2C7%2C4759%2C2845&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A study showed that an endangered population of beluga whales in the St. Lawrence River had one of the world's highest concentrations of the flame retardant, PBDE, in their blubber. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Flame retardants are added to a variety of products to prevent or slow the spread of fire. They have been added to many consumer and industrial products, including building materials, plastics, polyurethane-based foams in furniture, textiles and automotive parts, and electrical and electronic devices. They’re even in your iPhone.</p>
<p>Unfortunately, these product requirements are often poor predictors of actual fire risks and frequently lead to the misuse of these toxic chemicals. </p>
<p>When people dispose of consumer products that contain flame retardants, these chemical compounds end up in the environment, and contaminate, among other places, the St. Lawrence River, its estuary and wildlife. They can also travel great distances through the air to remote regions, including the Arctic. Flame retardants are now found in almost all species studied in the St. Lawrence River.</p>
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<img alt="" src="https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em>This article is part of our series, <a href="https://theconversation.com/ca-fr/topics/fleuve-saint-laurent-116908">The St. Lawrence River: In depth</a>.
Don’t miss new articles on this mythical river of remarkable beauty. Our experts look at its fauna, flora and history, and the issues it faces. This series is brought to you by <a href="https://theconversation.com/ca-fr">La Conversation</a>.</em></p>
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<p>In animals, exposure to certain types of flame retardants is associated with hormonal disruption, and developmental and reproductive disorders. Halogenated flame retardants (those containing bromine or chlorine atoms) are among the most widely used and environmentally harmful. </p>
<p>Many of them have now been banned, including polybrominated diphenyl ethers (PBDEs), but a new generation of alternative flame retardants are taking their place. Their environmental impacts have not been sufficiently tested and are likely to cause similar effects.</p>
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À lire aussi :
<a href="https://theconversation.com/these-chemicals-are-bad-for-babies-and-whales-why-havent-they-been-banned-in-canada-84951">These chemicals are bad for babies and whales: Why haven't they been banned in Canada?</a>
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<p>As a researcher in ecotoxicology, I focus part of my work on flame retardants in the environment and their impact on wildlife, including three of Québec’s iconic species: northern pike, minke whale and beluga whale.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A dark whale dives below the water surface, with a dart sticking into its side." src="https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462874/original/file-20220512-26-ylunm5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Using a crossbow, an arrow with a biopsy stinger is shot into the minke whale’s flank to collect a sample of skin and blubber.</span>
<span class="attribution"><span class="source">(Mériscope)</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<h2>St. Lawrence wildlife at great risk</h2>
<p>When ingested or inhaled, PBDEs accumulate in animal tissues over time. Their concentrations are on the rise in species at the top of the food chain, especially in densely populated, heavily polluted areas. </p>
<p>River-dwelling organisms are exposed to flame retardants in municipal waste from large urban areas. For example, Northern pike, a predatory fish, which are exposed to effluent from Montréal’s wastewater treatment plant, had liver PDBE concentrations four times higher than northern pike at an <a href="https://doi.org/10.1016/j.aquatox.2017.08.003">upstream river site</a>. New flame retardants (replacements for PBDEs), such as chlorinated chemicals that are similar to dechloranes and used mostly in cable and electrical wire sheathing, were also measured in these pike.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close up with two gloved hands removing a tissue sample from a small container using forceps." src="https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462873/original/file-20220512-22-ag49ef.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The research team removes the stinger biopsy.</span>
<span class="attribution"><span class="source">(Mériscope)</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>A study conducted downstream of major urban centres in the St. Lawrence estuary on beluga whales, a population currently considered endangered, revealed PBDE concentrations in their blubber that <a href="https://doi.org/10.1016/j.envres.2017.03.058">are among the highest in the world in marine mammals</a>. These concentrations do not appear to be decreasing despite the nearly 15-year-old ban on the use of PBDEs.</p>
<p>In comparison, PBDEs in beluga fat were measured at concentrations about four times higher than in minke whales, a baleen whale that is a seasonal visitor to the St. Lawrence estuary. A number of next-generation flame retardants were also measured in the blubber of belugas and minke whales in the estuary. History is repeating itself.</p>
<h2>Possible impacts on animal health?</h2>
<p>PBDEs are toxic to animals upon exposure. Without confirming causal links, wildlife studies indicate that exposure to flame retardants are associated with a range of harmful bodily effects on their hormonal, immune and metabolic functions, and consequently on growth, reproduction and development. This is partially confirmed by studies on the impacts of flame retardants in St. Lawrence pike, beluga and minke whales.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two people sit in a small boat collecting and organizing tissue samples." src="https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462872/original/file-20220512-21-3ysdwm.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">After separating the skin from the blubber in the whale biopsy, the research team quickly processes the samples to prevent their degradation.</span>
<span class="attribution"><span class="source">(Mériscope)</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>For pike, exposure to flame retardants in Montréal’s effluent affected the regulation of their thyroid hormones and decreased the expression of some liver genes involved in <a href="https://doi.org/10.1016/j.aquatox.2020.105421">lipid metabolism</a>. Lipids are important sources of energy for several biological functions.</p>
<p>In belugas and minke whales, exposure to flame retardants, including some emerging compounds, has also been associated with hormonal effects. Researchers have found links between the concentrations of some flame retardants, such as PBDEs, in these two cetaceans, thyroid hormone levels and the expression of genes that play a key role in regulating the steroid and thyroid hormones involved in <a href="https://doi.org/10.1016/j.marpolbul.2019.05.029">reproduction</a> and <a href="https://doi.org/10.1016/j.scitotenv.2020.137204">metabolism</a>.</p>
<p>However, chemical pollution in these species goes far beyond flame retardants. The cocktail of contaminants in the environment grows more complex year after year, and many of these accumulate in the tissues of marine animals, potentially creating compounding and even synergistic effects. </p>
<p>Sadly, the cycle of inadvisable substitutions — the replacement of one toxic compound with another that may eventually be deemed toxic in turn — seems to continue.</p>
<p>And that’s not good news for the health of our mighty St. Lawrence River and its priceless wildlife.</p><img src="https://counter.theconversation.com/content/184718/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Verreault has received funding from Fisheries and Oceans Canada and the Natural Sciences and Engineering Research Council of Canada (NSERC).</span></em></p>Flame retardants are added to consumer products — and end up in the environment and harming aquatic wildlife.Jonathan Verreault, Professeur titulaire, Centre de recherche en toxicologie de l’environnement (TOXEN), Université du Québec à Montréal (UQAM)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1845432022-06-12T12:11:42Z2022-06-12T12:11:42ZThe ocean is not a quiet place<figure><img src="https://images.theconversation.com/files/468299/original/file-20220610-43412-twobvv.jpg?ixlib=rb-1.1.0&rect=131%2C50%2C4725%2C3589&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The sound of the marine environment has been underestimated, mainly because it is not audible to the human ear.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>For a long time, the great ocean explorers used sight to reveal the secrets of the marine environment, downplaying its acoustic aspects. Indeed, the ocean has long been considered a place devoid of any sound.</p>
<p>This belief originated when Jacques-Yves Cousteau and his companions produced a remarkable feature film about the marine environment, <em>The Silent World</em>. Scuba divers often appear to be swimming through a calm and muffled universe, where communication between animals is done through through visual displays and chemistry. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/_OGECa4jFME?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Trailer for the documentary ‘Becoming Cousteau’, about the life and work of Jacques-Yves Cousteau.</span></figcaption>
</figure>
<p>Today, however, numerous studies underline the importance of sound for a multitude of marine species. Cetaceans — whales, dolphins and porpoises — are excellent ocean orators, capable of communicating at distances greater than 2,000 kilometres.</p>
<p>Even the smallest animals living at the bottom of the sea, which play a fundamental role in maintaining the balance of ecosystems, may communicate with each other through sound. I’m trying to answer this question as part of my doctoral studies at UQAR. Ultimately, we want to know if noise pollution has significant effects on the behaviour and communication of marine animals.</p>
<h2>Sound is essential to the life of marine animals</h2>
<p>Recent studies demonstrate that <a href="https://doi.org/10.1080/09524622.2022.2070542">the natural soundscape and the sounds emitted by the animals themselves play an important role in regulating different aspects of the life of marine invertebrates</a> (animals without an internal skeleton). From an early age, the tiny floating larvae of mussels, scallops and oysters seem to be influenced by the noise present in the environment around them. </p>
<p>Surprisingly, these larvae seem to be attracted to noises. For example, oyster larvae are more likely to settle in an environment exposed to sounds produced by their fellow creatures, as the sounds are an excellent index of <a href="https://doi.org/10.1080/09524622.2022.2070542">places conducive to life</a>.</p>
<hr>
<p>
<em>
<strong>
À lire aussi :
<a href="https://theconversation.com/can-an-underwater-soundtrack-really-bring-coral-reefs-back-to-life-128905">Can an underwater soundtrack really bring coral reefs back to life?</a>
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</em>
</p>
<hr>
<p>Sound also remains a fundamental aspect for the survival of animals in adulthood — and for their reproduction. Some species of molluscs can perceive their acoustic landscape to synchronize their seasonal spawning, and <a href="https://doi.org/10.1371/journal.pone.0185353">increase the chances of fertilization</a>. </p>
<p>For crustaceans, studies suggest that male European lobsters produce buzzing sounds <a href="https://doi.org/10.1242/jeb.211276">during competitive encounters</a> through low-frequency vibrations of the carapace to repel competitors. This communication strategy, adopted by different marine and terrestrial species to announce their presence to their adversaries, helps them avoid potentially costly and damaging physical confrontations.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A lobster among rocks." src="https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462575/original/file-20220511-26-o5ytpo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lobsters make buzzing sounds to avoid physical clashes with potential competitors.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Sounds can also be used by marine invertebrates warn each other of danger, such as a predator. The flapping of the valves of a fleeing scallop and the rhythmic beating of a sea slug against the shell bottom may be warning signals. When an octopus attacks a lobster, it tries to discourage the attacker by <a href="https://doi.org/10.3354/meps08957">making intimidating noises</a>.</p>
<h2>Ocean noise pollution: A major challenge</h2>
<p>Water is an excellent medium for sound propagation, <a href="https://doi.org/10.3354/meps08957">much better than air</a>, so it is realistic to think that a large majority of marine animals obey sound signals. Until now, this phenomenon has been largely overlooked, largely because many ocean sounds remain inaudible to our ears. The crab, however, may perceive the seabed as a long succession of different noises.</p>
<p>Many questions still remain unanswered for the moment, but technological progress will help scientists discover other wonders that the ocean still kept secret.</p>
<p>One thing remains certain: Human activities have introduced noise pollution into the marine environment, and organisms must find ways to adapt to this change. The construction of new infrastructure and the transport of goods are increasingly sources of noise pollution in our seas. </p>
<hr>
<p>
<em>
<strong>
À lire aussi :
<a href="https://theconversation.com/beluga-whistles-and-clicks-could-be-silenced-by-an-increasingly-noisy-arctic-ocean-151065">Beluga whistles and clicks could be silenced by an increasingly noisy Arctic Ocean</a>
</strong>
</em>
</p>
<hr>
<p>In the Far North, as <a href="https://doi.org/10.1016/j.marpolbul.2017.08.002">the sea ice melts</a> and new trade routes open up, new acoustic landscapes will be created. Their effects on local fauna will need to be evaluated. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Ship in an icy ocean" src="https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462576/original/file-20220511-14-jmmkm2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Marine cargo transport is a source of sound pollution.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Scientists have already shown that animal physiology and behaviour are affected by degrading its natural soundscape. Many species are extremely sensitive to anthropogenic (man-made) noise, which covers frequencies easily perceptible by marine invertebrates.</p>
<p>Knowing that the use of sound in the marine environment is much more widespread than previously thought, it is essential to understand the consequences of an increase in noise pollution in our oceans, and the noise that’s most harmful to life must be limited so that the ocean’s many inhabitants can return to their usual soundscape.</p><img src="https://counter.theconversation.com/content/184543/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Uboldi receives funding from the Institut France Quebec Maritime (IFQM) for his doctoral project.</span></em></p>The ocean is often considered a silent universe. But many recent studies highlight the importance of the soundscape for many marine species, both large and small.Thomas Uboldi, Phd candidate in Oceanography, Université du Québec à Rimouski (UQAR)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1596362021-05-03T20:07:24Z2021-05-03T20:07:24ZCurious kids: do whales fart and sneeze?<figure><img src="https://images.theconversation.com/files/398272/original/file-20210503-17-10vkbfa.png?ixlib=rb-1.1.0&rect=664%2C0%2C3329%2C2000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Wes Mountain/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><blockquote>
<p>Do whales fart and sneeze? — Guy, age 8, Sydney</p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>I’ve waited a long time for a question like this! I usually talk about whale snot for my research (yes, whales have snot), and I’m so excited to look into this, too.</p>
<h2>Let’s start with the tail end first: farts</h2>
<p>Yes, whales do fart. Can you imagine the size and bubbles of a fart from the world’s biggest animal, the blue whale? </p>
<p>I’m yet to experience this, but I know of some lucky scientists who have seen a humpback whale fart. They tell me it looks like bubbles coming out underneath its body near the tail. That’s where the whale bum is — the smellier blowhole. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/5mEePulli3c?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Most likely a humpback whale fart. Sound effect added.</span></figcaption>
</figure>
<p>Whales are <a href="https://australian.museum/learn/species-identification/ask-an-expert/what-is-a-mammal/">mammals</a>, just like us. This means they breathe air, give birth to live young, provide their young with milk and have hair, usually in the form of whiskers around their mouth. They also have digestive processes to help break down their food. </p>
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Read more:
<a href="https://theconversation.com/curious-kids-what-sea-creature-can-attack-and-win-over-a-blue-whale-98551">Curious Kids: What sea creature can attack and win over a blue whale?</a>
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<p>Unlike us, whales don’t chew their food but swallow it whole. <a href="https://www.smithsonianmag.com/science-nature/history-toothless-whales-180964717/">Baleen</a> or toothless whales, for example, use long hair-like structures to feed on krill and fish. Their food is later broken down across four stomach chambers. </p>
<p>As their bodies break this food down (via stomach acid), it produces gases, which are released as farts and eventually poo. </p>
<p>In fact, whale poo is one of the coolest looking in the animal kingdom. Blue whale poo can be bright orange! </p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CN8x-_FDyBb/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<h2>Back to the top end: do whales sneeze?</h2>
<p>The short answer, no. </p>
<p>Unlike us, whales need to think about breathing. When they want to take a breath, they need to swim to the surface. If they don’t, they could drown. </p>
<p>This means whales also <a href="https://www.scientificamerican.com/article/how-do-whales-and-dolphin/">sleep</a> differently to us. They can rest different parts of their brain at a time, and take naps before rising to the surface to breathe. </p>
<p>And unlike us, they can’t breathe through their mouth and instead use their blowhole or nose to breath. This is like having an inbuilt snorkel on top of their head. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-do-sharks-sneeze-77399">Curious Kids: Do sharks sneeze?</a>
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</p>
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<p>This makes it much easier for them to swim, breathe and eat — all at the same time. And they don’t have to worry about food going down the wrong way as their air and lung passages are separated. </p>
<p>We sneeze automatically and involuntarily if something tickles our nose. If whales get something caught in their noses, they could clear it using a big exhale through their blowhole, like blowing their nose. This would serve a similar function to our sneezing.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397733/original/file-20210429-23-178ee7e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A humpback whale takes a breath in Antarctica.</span>
<span class="attribution"><span class="source">Dr Vanessa Pirotta</span></span>
</figcaption>
</figure>
<h2>BUT, if a whale were to sneeze…</h2>
<p>It would be big! For comparison, an adult human’s lungs can hold around six litres of air. But a humpback whale can hold over 1,000 litres — that’s a lot of bubbles! </p>
<p>You can actually see a whale’s breath: it’s a mixture of lung bacteria, hormones, proteins and lipids. It’s officially called “whale lung microbiota” — or whale snot — and looks like water droplets. </p>
<p>As a scientist, I use <a href="https://www.frontiersin.org/articles/10.3389/fmars.2017.00425/full">drones</a> to sample whale snot to learn more about whale health. </p>
<p>We found the whales off Sydney didn’t even know their snot was being collected through this method. This is much safer for the whales and us as researchers as we don’t need to get close to each other. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/edS1uhO4LUw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Humpback whale snot collection via research drone off Sydney.</span></figcaption>
</figure>
<p>Well there you have it, we’ve covered both ends of a whale. They’re incredible creatures who do enormous farts — thanks for the question! </p>
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<strong>
Read more:
<a href="https://theconversation.com/curious-kids-have-people-ever-seen-a-colossal-squid-137398">Curious Kids: have people ever seen a colossal squid?</a>
</strong>
</em>
</p>
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<img src="https://counter.theconversation.com/content/159636/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vanessa Pirotta 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>Human farts and sneezes can be big — so imagine the size if they came from the world’s biggest animals?Vanessa Pirotta, Wildlife scientist, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1215282019-08-27T12:59:34Z2019-08-27T12:59:34ZWhat is the smallest animal ever?<figure><img src="https://images.theconversation.com/files/289135/original/file-20190822-170927-hfk4mc.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The world's smallest frog can fit on a dime.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Paratype_of_Paedophryne_amauensis_(LSUMZ_95004).png">E.N. Rittmeyer et al. (2012)</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&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"></span>
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What is the smallest animal ever? – Peter, age 9, Brookline, Massachusetts</strong></p>
</blockquote>
<hr>
<p>The biggest animal in the world is easy to see, if you know where to look. Living in every ocean except the Arctic, the blue whale is the <a href="https://www.natgeokids.com/nz/discover/animals/sea-life/10-blue-whale-facts/">largest animal on Earth</a> — weighing as much as 200 tons with a heartbeat that can be heard up to two miles away.</p>
<p>But the smallest animal in the world? Even if you knew where to look, could you see it? To track down the tiniest creature, scientists had to first decide what they were looking for and then, where they might find it. The first question – “What is an animal?” – is something that <a href="https://doi.org/10.1038/news060130-4">scientists have debated</a> for centuries.</p>
<p>I am an <a href="https://cvhs.okstate.edu/veterinary-medical-hospital/small-animal/avian-exotics-and-zoo-medicine/di-girolamo-publications.html">exotic animal veterinarian</a> especially fascinated by these types of questions.</p>
<h2>What is an animal?</h2>
<p>In the language of science, an animal is an organism made of multiple cells. Cells are the building blocks of all living things – a human body, for example, is made up of trillions of cells. Some organisms, like bacteria, are made of just one cell. They are not considered animals. </p>
<p>The simplest single-celled creatures – including bacteria – are called prokaryotes. They don’t contain a nucleus, the feature that acts like the main control center for a cell. More complex cells have an enclosed nucleus. They are called eukaryotes. Anything from an earthworm to a zebra or you are all eukaryotes and all are considered animals.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=522&fit=crop&dpr=1 754w, https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=522&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/289168/original/file-20190823-170910-1wt2b01.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=522&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The blue whale is the largest animal in the world. But what is the smallest?</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?curid=17942391">NOAA Photo Library</a></span>
</figcaption>
</figure>
<h2>If it can’t be seen, does that count?</h2>
<p>Based on this definition, an animal can be something so small that it’s not possible to see without a microscope. This is definitely not something that you would probably call an “animal.” A recent discovery is an organism that is invisible to the eye, a parasitic jellyfish called Myxozoa. They are very small and reaching barely 20 micrometers. Stretched out end to end, it would take more than 1,000 of these creatures to equal 1 inch.</p>
<p>Probably the smallest of these parasitic jellyfish is <em>Myxobolus shekel</em>, which <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4900514/">is no more than 8.5 micrometers when fully grown</a>.</p>
<p>This species was described in 2011, so is pretty new. So is the decision that Myxozoa are related to jellyfish, which scientists agreed on in 2015. The discovery of these types of jellyfish <a href="https://www.ncbi.nlm.nih.gov/pubmed/27330981">occur once in a while</a>, so it is possible that a new and even smaller animal will be discovered in the future.</p>
<h2>The process of elimination</h2>
<p>Let’s assume that you’re looking for the smallest “animal” that is visible to the human eye. Some invertebrates, or animals without a backbone, and other smaller organisms are not visible to the human eye. What is left are vertebrates, animals with backbones that include mammals such as a dog, a whale or you, reptiles such as snakes or crocodiles, birds, fishes and amphibians. <a href="https://www.nationalgeographic.com/animals/amphibians/">Most amphibians</a>, like frogs, are born in water and breathe with gills until they mature, when they develop lungs and an ability to live on land. </p>
<p>In this group of animals, it is the amphibians that win the prize for the smallest animal known, for the moment.</p>
<p>Scientists traveled to New Guinea, the second largest island in the world, to study the the island’s wildlife. This is where they found the smallest known type of frog called <em>Paedophryne amauensis</em>. The body length of an average adult is reported at less than 8 mm, <a href="https://www.nationalgeographic.com/news/2012/1/120111-smallest-frogs-vertebrates-new-species-science-animals/">about the size of a pea</a>. When it was discovered in 2009, it was immediately awarded the title of “<a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0029797">world’s smallest vertebrate</a>.”</p>
<p>The smallest animal is a question that scientists have debated for many years. Don’t worry. The nature of science means the answers will keep changing as researchers make new discoveries. Maybe a smaller vertebrate will be discovered in a quiet forest, on an exotic island, at the bottom of a canyon or in the dark abyss of the ocean. Scientists will keep looking.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.</em>
<em>Please tell us your name, age and the city where you live. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/121528/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicola Di Girolamo 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>Scientists have identified the world’s smallest animal – for now. It could be possible smaller creatures exist that have not yet been discovered.Nicola Di Girolamo, Associate Professor of Veterinary Clinical Sciences, Oklahoma State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/729852017-02-15T09:53:13Z2017-02-15T09:53:13ZWhat causes whale mass strandings?<p>Around 600 pilot whales recently became stranded on a <a href="http://www.telegraph.co.uk/news/2017/02/11/another-pod-whales-stranded-new-zealand-bringing-total-650/">New Zealand beach</a>, around 400 of which died before volunteers could refloat them back into the sea. Sadly, this kind of mass whale stranding has occurred since human records began, and happens somewhere in the world on a regular basis. </p>
<p>At the end of 2015, 337 sei whales died in a fjord in Chile after the largest ever beaching of whales <a href="http://news.nationalgeographic.com/2015/11/151120-worlds-largest-whale-stranding-sei-chile-animals/">of this species</a>. Mass strandings can also occur in northern Europe. In February 2016, 29 sperm whales were found stranded on the coasts of <a href="http://www.seawatchfoundation.org.uk/largest-sperm-whale-stranding-ever-recorded-in-the-north-sea/">Germany, the Netherlands, eastern England, and northern France</a>, a record for this species in the North Sea.</p>
<p>Why do these creatures, which are masters of living in a totally aquatic environment, enter an inhospitable land environment where inevitably some, if not all, will die?</p>
<p>Mass strandings almost invariably involve oceanic species of whales. Long-finned and short-finned pilot whales tend to be the most frequent casualties. Other species typically are false killer whales, melon-headed whales, Cuvier’s beaked whales and sperm whales. All of these normally live in waters over 1,000 metres deep and are very social, forming cohesive groups that in some cases may number hundreds of animals. </p>
<p>Although it’s tempting to automatically blame whale strandings on human activity, the fact that deep-dwelling species of whales most often get stranded, and in the same locations, indicates that in many cases natural causes are more likely to be to blame. Mass strandings of these oceanic species tend to be in very shallow areas with gently sloping, often sandy, seabeds. In those situations, it is no surprise that these animals, which are used to swimming in deep waters, can get into difficulties and even if re-floated will often re-strand.</p>
<p><a href="http://www.afsc.noaa.gov/nmml/education/cetaceans/cetaceaechol.php">The echolocation</a> they use to aid navigation also does not work well in such environments. So it is quite possible that the majority of such strandings are simply due to navigational error, for example when whales have followed a valuable prey resource into unfamiliar and dangerous territory. This may have been the cause of the mass stranding of sperm whales in the North Sea, some of which had recently digested oceanic squid in their stomachs.</p>
<p>The ratio of strandings to sightings for sperm whales in the North Sea is significantly higher south of the Dogger Bank where shallow, often sandy, <a href="http://www.seawatchfoundation.org.uk/largest-sperm-whale-stranding-ever-recorded-in-the-north-sea/">environments prevail</a>. And the same goes for Farewell Spit, Golden Bay in the South Island of New Zealand, where the recent pilot whale stranding took place and where <a href="http://www.bbc.co.uk/news/world-asia-16675613">similar incidents</a> <a href="http://www.bbc.co.uk/news/world-asia-31450651">have occurred</a> <a href="http://news.bbc.co.uk/1/mobile/world/asia-pacific/8432260.stm">several times</a> in the last few years. </p>
<p>Both areas have seen a number of mass strandings of those particular species in the past. In the southern North Sea, there are records of mass strandings of sperm whales dating back <a href="http://www.ecomare.nl/en/encyclopedia/organisms/animals/mammals/cetaceans/whales/sperm-whale/">at least to 1577</a>.</p>
<p>However, mass strandings aren’t only caused by whales getting lost or misjudging the depth of the water. One or more individuals may be diseased and, as they become weaker, they seek shallower waters so they can more easily come to the surface to breathe. Once their bodies come to rest on a hard surface for any extended period, there is a greatly increased chance that their chest walls will be compressed and their internal organs damaged.</p>
<h2>Sonar effects</h2>
<p>Occasionally, live strandings may derive from human activities, particularly military activity that involves the <a href="http://acousticstoday.org/wp-content/uploads/2015/05/Sonars-and-Strandings-Are-Beaked-Whales-the-Aquatic-Acoustic-Canary.pdf">use of sonar</a>. This connection was <a href="http://www.pelagosinstitute.gr/en/pelagos/pdfs/Frantzis%202003%20Active%20Sonar%20Workshop.pdf">first suggested</a> in 1996 after a NATO military exercise off the coast of Greece coincided with the stranding of 12 Cuvier’s beaked whales. Unfortunately, there was no opportunity for veterinary examination. </p>
<p>But <a href="http://www.nmfs.noaa.gov/pr/pdfs/health/stranding_bahamas2000.pdf">in May 2000</a>, another beaked whale mass stranding took place in the Bahamas alongside naval activity using similar loud mid-frequency sonar. A number of the whales were examined, and haemorrhaging, particularly around the inner ear, was discovered, indicating acoustic trauma.</p>
<p>After a similar incident in the Canary Islands in September 2002, veterinary pathologists analysing the whales also identified symptoms of <a href="http://journals.sagepub.com/doi/abs/10.1354/vp.42-4-446">decompression sickness</a>. This suggests that the animals do not always die from stranding but may be injured or die at sea first. Many researchers <a href="http://www.seawatchfoundation.org.uk/wp-content/uploads/2012/08/Active_Sonar_Workshop.pdf">now believe</a> that naval sonar might produce behaviour in whales that interferes with their ability to manage the gases inside their bodies, affecting their ability to dive and rise to the surface safely.</p>
<p>Loud noise in the ocean has become a major conservation concern as humans introduce sounds of varying intensities and frequencies into the marine environment from different technologies and even explosions. Seaquakes are another source of intense underwater sound and those might also lead to physical damage or behaviour resulting in strandings, although no one has yet produced a statistical link between the two. </p>
<h2>Social following</h2>
<p>The kind of strandings seen in New Zealand, where very large numbers of whales become beached but a significant proportion can be rescued, also raises the question of whether some healthy animals simply follow others into dangerously shallow waters.</p>
<p>Many years ago, I went to the aid of two short-beaked common dolphins that stranded alive in the Teifi Estuary, west Wales. One of the individuals died quite quickly and a subsequent post-mortem revealed it had a heavy lung parasite infection, which was thought to have affected breathing. The other individual remained close to its dying companion and appeared to be in great distress, whistling frequently.</p>
<p>We managed to successfully refloat this other dolphin in the end and it swam away, but the incident highlighted to me the strong social bonds that can exist between individuals. When we see large numbers of whales or dolphins undertaking what appears to be <a href="https://theconversation.com/do-whales-attempt-suicide-50165">mass suicide</a>, the chances are that they are vocally responding to one another, reflecting <a href="http://press.uchicago.edu/ucp/books/book/chicago/C/bo12789830.html">their strong sociality</a>.</p>
<p><a href="http://jhered.oxfordjournals.org/content/104/3/301.short">Recent research</a> suggests that whales in mass strandings aren’t necessarily even related to one another. So perhaps mass strandings are a reflection of just how strong the social bonds between whales really are.</p><img src="https://counter.theconversation.com/content/72985/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Evans 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>More than 400 whales have died on a beach in New Zealand.Peter Evans, Honorary Senior Lecturer, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/602842016-06-02T15:03:02Z2016-06-02T15:03:02ZHow insight into southern Africa’s dolphins is being deepened<figure><img src="https://images.theconversation.com/files/125000/original/image-20160602-23298-phwk0g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some dolphins live close to the shore, where they regularly encounter humans. This is affecting their numbers.</span> <span class="attribution"><span class="source">Simon Elwen</span></span></figcaption></figure><p><em>South Africa has a wide range of oceanographic conditions around the coast. As a result, there is a diversity of cetacean species. These are large-bodied, fast-moving top predators like dolphins and whales. Globally, at least a quarter of these species are listed as endangered. Understanding how these species move and live is crucial to understanding their ecological relationships with the environment.</em> </p>
<p><em>The E3C – Effect of Climate Change on Cetaceans – <a href="https://seasearchafrica.wordpress.com/2016/03/29/mapping-dolphin-distribution-using-citizen-science/#more-526">project</a> looks at the impact climate change has on these species. The Conversation Africa’s energy and environment editor Ozayr Patel spoke to Dr Simon Elwen, a researcher with South Africa’s University of Pretoria working on the project.</em></p>
<p><strong>Globally, at least a quarter of whale and dolphin species have been listed as endangered. What are the main reasons?</strong></p>
<p>Many of the large whale species and populations that were subjected to commercial whaling have been very slow to recover, notably the Antarctic blue whale and the North Atlantic right whale. But the majority of large whale populations have been increasing slowly over the past few decades. Species are gradually leaving the threatened lists, thanks to wide-ranging international conservation efforts. The most important of these is the end of whaling, showing that stopping directed take – in other words “not killing animals” – is one of the most effective conservation strategies. </p>
<p>But the bad news is that many dolphin and porpoise populations are the ones now facing extirpation. The Maui’s dolphin of New Zealand and the vaquita of the gulf of California are both critically <a href="http://www.hectorsdolphins.com/news-releases.html">endangered</a>. The baiji, the Chinese river dolphin, has already been declared extinct due almost entirely to habitat loss in the <a href="http://news.nationalgeographic.com/news/2006/12/061214-dolphin-extinct_2.html">Yangtze River in China</a>. </p>
<p><strong>What is the state of dolphin species around Africa’s coasts? What threats do they face?</strong></p>
<p>In southern Africa most dolphin populations are thought to be fairly healthy. There are five species that are regularly seen from shore, including the Heaviside’s and dusky dolphin on the west coast and the Indo-Pacific bottlenose and Indian Ocean humpback dolphin, which are found to the east of Cape Point in Cape Town. There are several other species that inhabit the shelf and offshore waters, with the common dolphin being one of the few of these regularly seen close to shore, especially along the south-eastern part of the continent. The only species that is currently thought to be of concern is the <a href="http://www.sousaproject.org/">humpback dolphin</a>, <em>Sousa plumbea</em>. </p>
<p>The humpback dolphin lives along the southern Cape coast and off northern KwaZulu-Natal province. This entire population in South Africa likely numbers less than 1,000 individuals and lives extremely close to shore, where it regularly encounters humans. This results in things like boat traffic, pollution, habitat loss and prey depletion having an impact on these species. </p>
<p><strong>Why are dolphins, in particular, important in the ocean’s ecosystem?</strong></p>
<p>Dolphins and whales are large, highly mobile top predators. They can eat a lot of food and respond quickly to changes in the environment by moving large distances, depending on the species. As large predators, they can have a top-down role in ecosystems, suppressing the numbers of prey animals. What this means is that sometimes species near the bottom of the food chain, like sardine or anchovy, can increase when medium-level predators are removed by top predators such as seals, sharks and dolphins, a result shown in a number of ecosystems globally.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125001/original/image-20160602-23298-1n81plu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dolphins and
whales are known to be top predators.</span>
<span class="attribution"><span class="source">Simon Elwen</span></span>
</figcaption>
</figure>
<p><strong>What is unique about the South African coast that makes it so diverse?</strong></p>
<p>South Africa’s marine life at all trophic levels is remarkably diverse, thanks largely to the diversity of habitats available around the coast. It ranges from tropical at the Mozambique border, to temperate along the south coast and cool-temperate along the west coast. </p>
<p>From a mammal point of view, the cold waters of the Benguela ecosystem along the west coast provide a link to sub-Antarctic environments, so some species that are usually only found south of 40 degrees of latitude also occur in the Benguela, like southern right whale dolphins and pygmy right whales.</p>
<p><strong>Commercial fishing practices, gill nets and pollution are viewed as the most serious challenge to dolphins. Are these serious problems in African and South African waters?</strong></p>
<p>To the best of my knowledge, bycatch – the unintentional catching of a species – is thankfully not a major problem in South Africa. There is no gill netting in South Africa. Coastal net fisheries are scarce and most of the large-scale commercial fishing activities in South Africa occur in deeper waters than most of our coastal dolphin species occur.</p>
<p>But entanglement in lobster and octopus trap lines is an increasing concern for large whales in coastal waters. Recent data on organic pollutants in dolphins from the east coast suggests that DDT and polychlorinated biphenyls are <a href="http://pubs.acs.org/doi/pdf/10.1021/acs.est.5b06009">still a concern</a>, especially for coastal dolphin species like the humpback and bottlenose. </p>
<p><strong>What effect is climate change having on dolphins?</strong></p>
<p>Essentially, assuming no other changes in the ecosystem – which is somewhat naive – we expect a general pole-ward shift in the distribution ranges of most cetacean species. This isn’t likely to be a major problem for animals that move large distances in the relatively uniform and connected environment of the open ocean. But it will potentially have major impacts on some coastal species, especially those that live in habitats that are “dead ends” in this respect (like the southern coast of Africa).</p>
<p>Along the South African coast, several dolphin species live in the Benguela, which is currently thought to be cooling – against the general trend of climate change – due to increased winds and upwelling of cold water. Right now we don’t really know how adaptable these animals are to massive changes in temperature in either direction, should they occur.</p>
<p><strong>What other major conservation tactics are used to help dolphins survive and thrive?</strong></p>
<p>1) Don’t kill them! In any form, including entanglement or bycatch, hunting or pollutants.</p>
<p>2) Stop polluting the oceans – including noise, plastics and organic pollutants.</p>
<p>3) Stop harassing them – obey the laws and use responsible tour operators.</p>
<p>4) Don’t steal their food – eat <a href="http://wwfsassi.co.za/">sustainably</a> caught fish </p>
<p><strong>You have started a project involving citizen scientists. Why have you taken this route?</strong></p>
<p>Citizen science projects have been extremely successful both locally and internationally. Modern communication methods like mobile phones and the internet allow scientists to rapidly communicate with thousands of interested and knowledgeable observers to increase the number of eyes and ears available to collect data. We can’t be everywhere, and our boat surveys and acoustic methods are limited in the amount of area or time they can cover, so we are trying to take advantage of the large number of keen whale and dolphin watchers around our Cape Town’s coasts to report sightings to us.</p>
<p>Remarkably, the area around Cape Town itself has been quite poorly studied by cetacean scientists in the past. So citizen science offers us a potentially powerful route to massively increase the number of data points of dolphin and whale sightings around the area.</p><img src="https://counter.theconversation.com/content/60284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Elwen works for the University of Pretoria and runs the Sea Search Africa research group. He receives funding from the National Research Foundation amongst others. </span></em></p>Globally, a quarter of whale and dolphin species are endangered. Though South African dolphin populations are generally in good heath, the humpback dolphin is cause for concern.Simon Elwen, Research Fellow, Mammal Research Institute, University of PretoriaLicensed 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.