tag:theconversation.com,2011:/uk/topics/grey-squirrels-19738/articlesGrey Squirrels – The Conversation2024-02-21T13:04:38Ztag:theconversation.com,2011:article/2232242024-02-21T13:04:38Z2024-02-21T13:04:38ZGut bacteria may explain why grey squirrels outcompete reds – new research<p>Across large parts of the UK, the native red squirrel has been replaced by the grey squirrel, a North American species. As well as endangering reds, grey squirrels pose a threat to our woodlands because of the damage they cause to trees. </p>
<p><a href="https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.001793">New research</a> from my colleagues and I compared the gut bacteria of red and grey squirrels. We found that differences between the two may explain their competition and red squirrel decline, as well as why grey squirrels are so destructive to woodland.</p>
<p>Grey squirrels were introduced to the UK between 1876 and 1929 and have displaced reds in most areas of the UK. Greys carry a virus called “squirrelpox”, which doesn’t affect them but leads to sickness and often death in red squirrels.</p>
<p>Grey squirrels are bigger than red squirrels and compete with them <a href="https://www.frontiersin.org/articles/10.3389/fevo.2023.1083008/full">for food and habitat</a>.
Acorns, a widespread food source, contain tannins, which are hard for red squirrels to digest. But greys can digest acorns easily, giving them an extra edge in competing for resources. </p>
<p>Grey squirrels frequently strip the bark from deciduous trees. In commercial plantations, the damage can lead to fungal infection and result in the tree producing low quality timber. The annual cost is an <a href="https://rfs.org.uk/insights-publications/rfs-reports/report-overview-the-cost-of-grey-squirrel-damage-to-woodland-in-england-and-wales/">estimated £37 million.</a> with sycamore, oak, birch and beech frequently targeted. </p>
<p>The grey squirrels select the strongest growing trees as these have bark containing the largest volume of sap. Intriguingly, grey squirrels do not select trees with the <a href="https://www.researchgate.net/publication/230344319_Bark-stripping_by_Grey_squirrels_Sciurus_carolinensis">highest sugar content</a>. This observation has led scientists to posit that the squirrels consume bark to obtain <a href="https://www.sciencedirect.com/science/article/pii/S0378112716300421?via%3Dihub">certain micro-nutrients</a>. </p>
<h2>Gut bacteria</h2>
<p>All mammals have microorganisms living in their intestines. For example, the typical human colon is host to at least <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5847071/">160 bacterial species</a>, while in birds, research has found thousands of different bacterial species in <a href="https://pubmed.ncbi.nlm.nih.gov/33868800/">chicken intestines.</a></p>
<p>The bacteria break down foods and help synthesise vitamins, complementing the enzymes secreted by the body. The diversity of these microorganisms, known as the “microbiota”, can reflect the level of health and also the diet of an individual. But we don’t know enough about the microbiota living in squirrel intestines. </p>
<p>The types of microbes present vary between species, yet the extent to which they differ between grey and red squirrels is unclear. We explored this and investigated the potential for any differences to affect competition between the two squirrel species. We also examined whether gut bacteria might be playing a role in bark stripping behaviour.</p>
<p>We sampled bacterial DNA from red and grey squirrel intestinal contents and performed gene sequencing to identify the range of bacteria present in the samples. The results were analysed to compare any important differences between the two.</p>
<figure class="align-center ">
<img alt="A cute red squirrels with a large bushy tail stands on the branch of a tree." src="https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=430&fit=crop&dpr=1 600w, https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=430&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=430&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=541&fit=crop&dpr=1 754w, https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=541&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/576545/original/file-20240219-20-ivfdqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=541&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ynys Môn off the north Wales coast is one of the few places in the UK where greys have been eradicated in favour of red squirrels.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/red-squirrel-views-around-north-wales-2232607907">Gail Johnson/Shutterstock</a></span>
</figcaption>
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<h2>Calcium</h2>
<p>Calcium is an important nutrient in the body and is required for healthy bones, muscles and nerves. It is especially needed by lactating animals and ones that are young and growing.</p>
<p>We found that grey squirrels may have the capacity to obtain the calcium that exists in tree bark thanks to the presence of a bacteria called “oxalobacter” in their gut. The calcium in tree bark comes in an insoluble form and is hard for an animal to digest. But oxalobacter would be able to change this into a form that could be more digestible. </p>
<p>Calcium levels <a href="https://www.sciencedirect.com/science/article/pii/S0378112716300421?via%3Dihub">increase in trees</a> as active growth resumes after winter dormancy. This happens immediately before the main squirrel bark-stripping season of May to July. Our research may therefore help to explain the destructive behaviour of grey squirrels and why red squirrels appear to strip bark much less frequently.</p>
<p>Our research also identified a significantly higher diversity of bacteria in the intestines of grey squirrels compared to red squirrels. This could hold the key to further understanding why grey squirrels outcompete red squirrels in the UK. </p>
<p>A more diverse range of bacteria being sustained in the gut means that grey squirrels potentially may be able to access a broader range of resources than red squirrels in addition to acorns.</p>
<h2>Adenovirus</h2>
<p>The grey squirrel harbours not just the squirrelpox virus, but also another potential threat – adenovirus. While this virus causes severe intestinal lesions in some red squirrels, curiously, grey squirrels never exhibit the same symptoms.</p>
<p>This discrepancy underscores the fascinating and complex potential role of gut microbiota. Research increasingly reveals their influence on everything from digestion to immune response, and even susceptibility to disease.</p>
<p>In the context of red squirrels, understanding how variations in their gut bacteria might predispose them to adenovirus becomes crucial. This is especially pertinent for captive breeding programs, where adenovirus infections pose a hurdle to successful reintroductions of red squirrels into the wild.</p>
<p>Given we only sampled red and grey squirrels from north Wales, we hope that future studies will map the gut microbiota of other European populations too. Such future research will continue to improve our knowledge of the competition between red and grey squirrels.</p><img src="https://counter.theconversation.com/content/223224/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig Shuttleworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research suggests the gut bacteria of red and grey squirrels differ significantly, potentially explaining the decline of the native red and the success of its grey counterpart.Craig Shuttleworth, Honorary Visiting Research Fellow, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2036032023-04-18T16:12:03Z2023-04-18T16:12:03ZPablo Escobar’s ‘cocaine hippos’ are a problem – but a lot of thought is going into preventing their spread<p>Last week, Colombia recorded its first road traffic incident involving a hippopotamus. A <a href="https://www.theguardian.com/world/2023/apr/12/calls-action-on-colombia-hippo-scourge-animal-dies-road-crash">car collided with the animal</a> at speed leaving it dead on the road. </p>
<p>The hippo was a descendent of the four animals that notorious drug lord Pablo Escobar <a href="https://www.cambridge.org/core/journals/oryx/article/potential-ecological-and-socioeconomic-effects-of-a-novel-megaherbivore-introduction-the-hippopotamus-in-colombia/8191CD050B5208617BA834D394145AC1">imported from a zoo in the US</a> to his luxurious Hacienda Nápoles estate in Colombia in the 1980s. The four hippos, which included three females and one male, were abandoned after Escobar’s death in 1993 due to the difficulty associated with moving them to a wildlife sanctuary. The hippos then escaped the untended estate and spread along the <a href="https://archive.internationalrivers.org/campaigns/magdalena-river">Magdalena River</a>. </p>
<p>They have since bred and have multiplied to <a href="https://apnews.com/article/colombia-hippopotamus-relocation-mexico-india-4bb9441be82839b4f10dd89c748d1bd3">around 130 animals</a>. But in the wild, the hippos are fast becoming a problem. Hippo attacks on people are <a href="https://news.mongabay.com/2022/02/in-colombia-escobars-hippos-spawn-another-problem-wildlife-trafficking/#:%7E:text=While%20the%20animal%20is%20notorious,to%20hippo%20attacks%20in%20Colombia.">on the rise</a> and an illegal trafficking industry has developed around their capture and sale. </p>
<p>Ecologists also warn that large herbivores such as hippos are upsetting Colombia’s delicate aquatic ecosystems. By excreting waste into lakes and rivers, hippos can <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2991?casa_token=MLHTg_aPhh0AAAAA%3ALDgaJSsh6wBZIH-Xf9w1FVcJTlJ_6ndASRxnxJ_BSMby62VOLK5HGPY4ghKlCeyiccPEN87mQPS3dG_f">change the composition</a> of the surrounding water. This water provides habitat for animals including <a href="https://www.britannica.com/animal/manatee#ref14338">manatees</a> and <a href="https://www.britannica.com/animal/capybara-genus">capybaras</a>.</p>
<figure class="align-center ">
<img alt="A group of hippos with their heads out of the water." src="https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=345&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=345&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=345&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=433&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=433&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520924/original/file-20230413-16-pj7fc2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=433&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Environmental authorities are concerned that the hippos may be degrading Colombia’s delicate aquatic ecosystems.</span>
<span class="attribution"><a class="source" href="https://openverse.org/image/eeedf590-2397-48e5-a9ec-f94e4bfd597b?q=hippo%20colombia">FICG.mx/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>The hippos are now <a href="https://www.minambiente.gov.co/wp-content/uploads/2022/05/Resolucion-0346-de-2022.pdf">officially listed</a> as an invasive species that need to be controlled. But how to best manage them has long troubled the country’s environment ministry. </p>
<h2>Managing Escobar’s hippos</h2>
<p>In 2009, the Colombian environmental agency ordered hunters to <a href="https://www.theguardian.com/world/2009/jul/14/hunters-kill-escobar-fugitive-hippo">kill three hippos</a> amid concerns they were damaging crops and endangering humans. A hippo, nicknamed Pepe, was killed as a result. Photos of the dead hippo went viral and <a href="https://www.cambridge.org/core/journals/oryx/article/potential-ecological-and-socioeconomic-effects-of-a-novel-megaherbivore-introduction-the-hippopotamus-in-colombia/8191CD050B5208617BA834D394145AC1">sparked a global outcry</a>.</p>
<p>The culling promptly ended and the fate of the remaining hippos is now to be decided by <a href="https://scholar.google.com/scholar_case?case=17167775334235737642&hl=en&as_sdt=2006">two ongoing legal cases</a>. I have analysed both cases as part of my research and it’s my opinion that they are evidence of good practise in controlling invasive species. This is because the <a href="https://www.mdpi.com/2075-471X/12/2/29#B11-laws-12-00029">interests of the animals</a> are being considered – a luxury that is not afforded to most invasive animal species.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0006320720309812">Three strategies</a> have been proposed to control Colombia’s hippo population: euthanasia, relocation to zoos and animal sanctuaries abroad and fertility control.</p>
<p>Euthanasia represents the cheapest and fastest method to control Colombia’s hippo population. It is, however, a controversial strategy and would involve up to 30 hippos a year being killed. Those who oppose the strategy argue that it is clearly not in the interests of the hippos.</p>
<p>The relocation programme instead involves moving 70 hippos to zoos and animal sanctuaries in <a href="https://apnews.com/article/colombia-hippopotamus-relocation-mexico-india-4bb9441be82839b4f10dd89c748d1bd3">India and Mexico</a> that are capable of caring for them. But hippos are aggressive and very large, so they are difficult to capture and transport. Many of those that remain will therefore have their fertility controlled.</p>
<p>The <a href="https://openargs.com/wp-content/uploads/2021.10.15-Escobar-hippos-Maldonado-decl.pdf">fertility control programme</a> will use a drug called Porcine Zona Pellucida to reduce the fertility of the female hippos. The same drug is used to control hippo birth rates in zoos. Such a strategy will reduce wild hippo numbers over longer periods of time and will eventually lower the threat they pose to people and the environment. </p>
<p>Used together, the fertility control and relocation strategies would help to control Colombia’s hippo population. And, though the animals would be in captivity or unable to raise offspring, the plans are more humane than the alternative of being killed.</p>
<figure class="align-center ">
<img alt="A group of hippos in water at a zoo." src="https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521565/original/file-20230418-22-fmudva.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hippo birthrates are already controlled in zoos.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/group-hippo-hippopotamus-water-zoo-1757747858">Mai.Chayakorn/Shutterstock</a></span>
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</figure>
<h2>Good invasive species management?</h2>
<p>These are not perfect solutions. Controlling hippo fertility will not immediately reduce the wild population. As a result, it risks prolonging the threat of conflict between humans and hippos. It also does little to protect the environment in the short term.</p>
<p><a href="https://openargs.com/wp-content/uploads/2021.10.15-Escobar-hippos-Maldonado-decl.pdf">Research</a> also suggests that between 70% and 80% of Colombia’s wild female hippos will need to be sterilised for the strategy to be effective. Sterilising this amount of hippos would eventually stabilise the population. But how long this would take has not yet been disclosed.</p>
<p>Both of these strategies are expensive. Relocating the hippos will cost around <a href="https://openargs.com/wp-content/uploads/2021.10.15-Escobar-hippos-Maldonado-decl.pdf">US$3.5 (£2.8) million</a>, and fertility treatment costs <a href="https://www.bbc.co.uk/news/world-latin-america-56011594">US$50,000</a> for each hippo. Funding may be diverted away from conservation efforts elsewhere in favour of humanely tackling Colombia’s rising hippo population. </p>
<h2>Moving Forward</h2>
<p>Invasive species tend to be <a href="https://books.google.co.uk/books?hl=en&lr=&id=jyiFDwAAQBAJ&oi=fnd&pg=PT11&ots=neCZG3zIB6&sig=i2pWbslynGj3YbrGFZGAyNG1qWI&redir_esc=y#v=onepage&q&f=false">perceived as threats</a> which need to be exterminated. Many countries allow invasive animals to be killed by any means necessary to control their population. Policies carried out with the aim of controlling these animals are therefore <a href="https://link.springer.com/article/10.1007/s10806-020-09825-0">often unethical</a>. </p>
<p>The Colombian hippo case demonstrates that invasive animal species can be controlled and have their interests taken into account at the same time. But it is important to recognise that when compared to other invasive species, these hippos may have been given preferential treatment. This likely stems from the high-profile nature of the case that, given its association to Pablo Escobar, has captured the attention of the public.</p>
<p>There are, however, some aspects of the Colombian hippo case that could be applied to invasive species management more broadly. When euthanasia is the preferred option, choosing methods that limit animal suffering should be prioritised. </p>
<p>Grey squirrels, for example, are considered a pest species within the UK and can be <a href="https://link.springer.com/article/10.1007/s10806-020-09825-0">legally killed</a> using methods such as poisoning and traps. But more humane alternatives, such as using oral contraceptives, exist that would also keep their population in check.</p>
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Read more:
<a href="https://theconversation.com/grey-squirrels-is-birth-control-the-solution-to-britains-invasive-species-problem-154400">Grey squirrels: is birth control the solution to Britain's invasive species problem?</a>
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<p>Colombia’s wild hippo population has become a problem. Inevitably, the species will need to be managed to avoid further harm to the animals, the wider environment and to prevent conflict with humans. </p>
<p>The case of Pablo Escobar’s invasive hippos is unique. Yet it could be seen as a step in the right direction for invasive species management. Despite the preferred management options being expensive and often failing to immediately curb the animals spread, they avoid unnecessary killings and encourage more creative solutions to emerge.</p><img src="https://counter.theconversation.com/content/203603/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elliot Doornbos 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>Pablo Escobar’s hippos escaped in the 1990s – since then, they have become a problem.Elliot Doornbos, Senior Lecturer of Criminology, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1968112022-12-21T17:08:14Z2022-12-21T17:08:14ZSquirrelpox outbreak detected in north Wales – without a vaccine, the disease will keep decimating red squirrels<p>Concerns over the spread of squirrelpox have increased after a <a href="https://www.bbc.co.uk/news/uk-wales-63865940">sick red squirrel was found in Bangor, Wales, in late November</a>. </p>
<p>It’s not the first time an outbreak has happened in the area – back in 2020/21, the disease caused a loss of <a href="https://www.mdpi.com/2076-2615/12/1/99">70%-80% of its red squirrel population</a>. Such major outbreaks are devastating and lead to <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.1216">dramatic and ongoing red squirrel declines</a>.</p>
<p>Conservationists have a formidable task to ensure that similar losses do not happen again. The current national strategy is simple: <a href="https://www.gov.wales/grey-squirrel-management-action-plan-for-wales">cull grey squirrels</a> in areas where red squirrels persist. However, there is no single, straightforward way to safeguard the future of this native mammal at the moment.</p>
<p>It is the grey squirrel which <a href="https://zslpublications.onlinelibrary.wiley.com/doi/10.1111/j.1469-1795.2000.tb00107.x">carries squirrelpox virus infection</a>, but it does not cause them obvious harm. When they were first introduced from North America during the Victorian era, <a href="http://www.italian-journal-of-mammalogy.it/pdf-126011-61760?filename=Introduced%20Canadian.pdf">grey squirrels brought the virus to Britain</a> and Ireland. </p>
<p>Grey squirrels compete for resources with <a href="https://www.bbc.co.uk/programmes/p0cc7l69">native red squirrels</a>, which is a species with <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1690913/pdf/11886647.pdf">little immunity to the virus</a>. The infection produces extensive skin lesions around the eyes, muzzle and mouth, on the digits and around the genitalia. The sores become infected by bacteria and are a major source of viral particles which contaminate the environment. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502171/original/file-20221220-17-dycnm8.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">Red squirrel with squirrelpox virus.</span>
<span class="attribution"><a class="source" href="https://flickr.com/photos/55426027@N03/14469405549">Peter Trimming / Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>This increases the likelihood of sick red squirrels spreading infection to other reds. Squirrelpox leads to <a href="https://www.cambridge.org/core/journals/epidemiology-and-infection/article/epidemics-of-squirrelpox-virus-disease-in-red-squirrels-sciurus-vulgaris-temporal-and-serological-findings/6543EE3ED2792F0C9CD188EE3973EED8">death within three weeks</a> of infection. </p>
<h2>Does culling work?</h2>
<p>On the island of Anglesey, off the northern coast of Wales, culling between 1998 and 2013 led to the <a href="https://www.independent.co.uk/climate-change/news/the-uk-island-which-has-completely-wiped-out-grey-squirrels-a6708781.html">eradication of grey squirrels</a>. As those efforts steadily reduced grey squirrel numbers, the proportion of remaining greys exposed to squirrelpox virus and showing <a href="https://link.springer.com/article/10.1007/s10530-014-0671-8">antibodies progressively dwindled</a> to zero, revealing that the virus eventually disappeared from their population.</p>
<p>With fewer hosts to infect, eventually the infection was simply unable to spread between hosts. Although red squirrels were reintroduced before the grey squirrel eradication was completed, the steady decline in levels of infection among grey squirrels explains why no diseased reds were found on the island.</p>
<p>Across Wales, an <a href="https://research.bangor.ac.uk/portal/en/researchoutputs/striving-for-success-an-evaluation-of-local-action-to-conserve-red-squirrels-sciurus-vulgaris-in-wales(1963b515-5120-482d-b11b-59da05c9457a).html">estimated 1,500 red squirrels</a> may remain. Whereas there were only <a href="https://cdn.naturalresources.wales/media/691092/eng-red-squirrel-conservation-plan-for-wales.pdf">40 on Anglesey in 1998</a>, today there are perhaps 800. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1597980163266195456"}"></div></p>
<p>In 2009, red squirrels were first recorded on the Gwynedd mainland having <a href="https://www.dailypost.co.uk/news/north-wales-news/red-squirrels-spotted-areas-first-13519515">crossed the narrow Menai Strait from Anglesey</a>. This population expanded but since 2017, there have been repeated <a href="https://www.bbc.co.uk/news/uk-wales-north-west-wales-42377351">squirrelpox outbreaks</a> there. </p>
<p>The problem with culling outside of a closed environment like an island is that, to be effective, control has to be coordinated over ever-larger areas, which is expensive and time-consuming. Sporadic or localised mainland grey squirrel culling simply leads to <a href="https://www.jstor.org/stable/20728617">rapid re-invasion</a>. </p>
<p>Red squirrels also naturally return to the habitats from where greys are removed. This inevitably leads to mixing and continued risk of infection.</p>
<h2>Birth control</h2>
<p>So what more can be done? A complementary, non-lethal population control method is being developed. This is an oral <a href="https://theconversation.com/grey-squirrels-is-birth-control-the-solution-to-britains-invasive-species-problem-154400">contraceptive bait</a> which, if consumed, makes grey squirrels infertile. It would be deployed in hoppers designed to only allow grey squirrels access.</p>
<p>Although this is an exciting prospect, research suggests effective use would <a href="https://www.sciencedirect.com/science/article/abs/pii/S0304380020304506">require grey populations to be reduced first by culling</a>, before the contraceptive is presented. Using bait will also require coordination between a multitude of landowners, not all of whom may wish to be involved or pay for control.</p>
<p>It is therefore an important part of a future solution, but not a simple panacea. </p>
<h2>Pine marten to the rescue?</h2>
<p>Another interesting possibility could be to use pine martens to control the grey population. The pine marten is being reintroduced into many parts of Britain <a href="https://linkinghub.elsevier.com/retrieve/pii/S2352249620300240">including woodlands adjacent to Anglesey</a>. The occasional individual has been <a href="https://www.dailypost.co.uk/news/north-wales-news/rare-squirrel-eating-predator-discovered-24466313">detected on the island</a> too. </p>
<p>Pine marten <a href="https://theconversation.com/grey-squirrels-are-oblivious-to-threat-from-pine-martens-giving-native-reds-the-advantage-131064">predation is more pronounced upon grey</a> than red squirrels, and this fact could lead to the suppression of the squirrelpox pathogen. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=352&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=352&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=352&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=443&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=443&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502129/original/file-20221220-20-w0zd44.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=443&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The pine marten is being reintroduced into many parts of Britain.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Recent <a href="https://www.sciencedirect.com/science/article/pii/S0304380022003143">mathematical modelling</a> has reinforced the potential role for this native predator in reducing the impact of invasive grey squirrels and the infectious diseases they harbour. <a href="https://linkinghub.elsevier.com/retrieve/pii/S2352249620300240">Research by myself and colleagues</a> suggests that grey squirrels would decline if pine martens are reintroduced, and often their numbers would then be insufficient for the virus to be maintained. </p>
<p>One uncertainty is exactly how much of an effect this predator would have, because it is omnivorous and hunts a wide variety of prey. When vole populations are high, for example, pine martens may focus their hunting on this prey, and <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/oik.08565">less on grey or red squirrels</a>. Nevertheless, pine marten recovery is likely to be a positive contribution to grey squirrel management and our modelling predictions are dramatic. </p>
<p>Unfortunately, both this and commercial contraceptive use are only likely to assist in the medium to long term. Consequently, we are currently left with expensive ongoing local culling programmes. </p>
<h2>A vaccine is essential</h2>
<p>A big gap in our ability to fight squirrelpox comes from the fact there is currently <a href="https://squirrelaccord.uk/squirrels/squirrel-pox-disease/">no vaccine available for the disease</a>. The <a href="https://www.wildlifearktrust.com/appeal.html">Wildlife Ark Trust</a> funded a vaccine development programme, but insufficient funding meant this research stopped a decade ago.</p>
<p>With no way to inoculate red squirrels against the pox virus, we can do little in the face of inevitable future squirrelpox outbreaks such as that which occurred near Bangor. It is to our collective shame that research halted because of insufficient funding and political will.</p><img src="https://counter.theconversation.com/content/196811/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>I have given long standing and public support for the Wildlife Ark Trust vaccine appeal. </span></em></p>There is no single, straightforward way to safeguard the future of this native mammal at the moment – but here are some optionsCraig Shuttleworth, Honorary Visiting Research Fellow, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1544002021-02-03T14:21:34Z2021-02-03T14:21:34ZGrey squirrels: is birth control the solution to Britain’s invasive species problem?<figure><img src="https://images.theconversation.com/files/382224/original/file-20210203-21-kb8tu8.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4020%2C2832&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/grey-squirrel-feeding-on-chestnuts-autumn-118390966">Scooperdigital/Shutterstock</a></span></figcaption></figure><p>There are thought to be 2.7 million grey squirrels in the UK, versus only 287,000 <a href="http://publications.naturalengland.org.uk/publication/5636785878597632">red squirrels</a>. The invasive greys, brought to Britain and Ireland from North America in the 1870s, are blamed for the disappearance of the native red throughout much of England and Wales, due to the squirrel pox virus they transmit and the fact that they compete for food and habitat with their smaller relatives.</p>
<p>As with the UK’s other invasive species, such as rabbits, signal crayfish and Japanese knotweed, introducing the grey squirrel has proved to be an expensive mistake. Not only do grey squirrels displace red squirrels, they strip bark from trees. <a href="https://rfs.org.uk/news/2020/1-2021/grey-squirrels-threatening-our-woodlands-to-tune-of-11bn/">A recent report</a> estimated that this could cost commercial forestry and native woodlands £1.1 billion (US$1.5 billion) over the next 40 years, including revenue lost to damaged timber, reduced carbon storage, tree replacement costs and squirrel control.</p>
<p>Despite efforts to kill grey squirrels over several decades, their populations remain large and widespread. So could <a href="https://www.bbc.co.uk/news/science-environment-55817385">government-backed plans</a> for using oral contraceptives to control their breeding be the turning point?</p>
<h2>Squirrel birth control</h2>
<p>Before we consider that question, let’s interrogate the idea that grey squirrels are bad for the environment because they damage trees. If we’re worried about carbon in the atmosphere then phasing out fossil fuels, not killing squirrels, is the top priority. And squirrels, even non-native greys, play an important role in woodlands by <a href="https://www.frontiersin.org/articles/10.3389/fevo.2020.00259/full">burying the nuts they find</a> and seeding new trees. If grey squirrels were to vanish overnight, then the natural regeneration of UK woodlands would probably slow.</p>
<p>Whether or not the damage caused by this invasive species is exaggerated, these reports inevitably encourage calls for bigger <a href="https://www.telegraph.co.uk/news/2021/01/21/royal-forestry-society-urges-grey-squirrel-cull-wake-1bn-woodland/">culls of grey squirrels</a>. Oral contraceptives might at least be a more humane alternative to live trapping and bludgeoning the animals to death.</p>
<p>Birth control has worked for keeping wildlife populations elsewhere in check. The method, which often involves injecting contraceptives, has proved successful in more than 85 species, including wild horses and elephants, according to <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1600-0897.2011.01003.x">a 2011 review</a>. Contraceptives halved dense and destructive populations of North American <a href="https://pdfs.semanticscholar.org/7383/a4c2227392c16c8c6269fd3e91fa65c728a4.pdf?_ga=2.143665589.1480929846.1612138237-212678758.1612138237">white-tailed deer</a> in under 10 years.</p>
<p>Research into using oral contraceptives on grey squirrels in the UK has been ongoing for <a href="https://squirrelaccord.uk/squirrels/fertility_control/">several years</a>, and recent results show promise. Trials using feeders that only grey squirrels can access, baited with hazelnut spread laced with an <a href="https://www.humanesociety.org/resources/questions-and-answers-about-immunocontraception">immunocontraceptive</a> (a drug which tricks the body’s immune system into producing antibodies that interfere with reproduction, by blocking the sperm receptor sites on eggs, for example) indicate that <a href="https://squirrelaccord.uk/news/blog/fertility-research-news-from-the-field/">around 90%</a> of a local population can be treated using this method. Researchers hope this could induce infertility to such an extent that treated populations shrink substantially over time.</p>
<p>Contraceptives have their own <a href="https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/csp2.171">ethical concerns</a> though. Being alive isn’t necessarily always better than being dead. We don’t really know what physiological and psychological effects an inability to breed will have on the welfare of grey squirrels.</p>
<p>It’s also important that this contraceptive doesn’t affect other species, though there are measures to ensure this. Bespoke feeding boxes that only grey squirrels can enter limit the risk to other species, in particular red squirrels, by weighting the door of the feeder so that the smaller red <a href="https://squirrelaccord.uk/news/blog/fertility-research-news-from-the-field/">cannot enter</a>. Providing the bait in a hazelnut spread, rather than nuts which squirrels may bury, prevents other animals inadvertently finding and eating the contraceptive. But what about predators? Will their fertility be threatened by eating prey dosed with contraceptives?</p>
<h2>The alternatives</h2>
<p>There are other ways to control grey squirrel populations, such as <a href="https://thebiologist.rsb.org.uk/biologist/158-biologist/features/2245-accelerating-evolution">gene drives</a>. These are altered genes that can be implanted in males and programmed to induce infertility in the genome of their female offspring. Female infertility spreads through the population as the gene drive is carried and inherited by males. Gene drives don’t carry the same risk of cross-contamination between species that contraceptives do, and they are cheaper and easier to implement.</p>
<p>But they still have a long way to go before they’re approved as a control method, as scientists worry that a gene drive could spread from invasive to native populations. Imagine a grey squirrel in the UK that had been treated with a gene drive somehow made it back into their native range in North America – it could mean their extinction.</p>
<p>Perhaps the most popular solution to the grey problem is the pine marten, a predatory mammal that is slightly larger than a ferret. Almost hunted to extinction in the UK, pine martens have made a comeback in recent years. <a href="https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2017.2603">Research suggests</a> that where martens return to woodland they reduce grey squirrel populations, while boosting the number of red squirrels. But pine martens aren’t going to colonise the entire country – and they are still predators which eat other wildlife and some domestic animals. Their return is likely to face <a href="https://www.scotlandbigpicture.com/rewilding-stories/the-return-of-the-taghan">resistance in some places</a>.</p>
<figure class="align-center ">
<img alt="A weasel-like mammal hugging a river bank to sip the water." src="https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/381704/original/file-20210201-19-1s9s592.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Pine martens are thought to hunt grey squirrels more readily than reds.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pine-marten-drinking-lake-forest-1798450855">Beata Farkas/Shutterstock</a></span>
</figcaption>
</figure>
<p><a href="https://reader.elsevier.com/reader/sd/pii/S0304380020304506?token=65D4E8A4AD5ED08A53E7A0359A31A65414B15AB18285A97E020D0CB976E7BF1A903F54EFACC860BFCCAEFAB5F95054B7">A recent study</a> suggested the most efficient way to control grey squirrels is a combination of culling and contraceptives. So no matter how effective an oral contraceptive is, culls are likely to continue. Animal welfare campaigners are <a href="https://petition.parliament.uk/petitions/562294">lobbying the government</a> to at least halt culls during the breeding season, when female grey squirrels have kits in the nest. As it stands, mothers can be killed and their offspring left to starve.</p>
<p>I’ve written <a href="https://theconversation.com/in-defence-of-the-grey-squirrel-britains-most-unpopular-invader-73983">in defence of grey squirrels</a> before, but I support controlling their populations with contraceptives. While I’d prefer nature to provide its own solution, I welcome methods of controlling so-called pest species that minimise pain and stress. Just because a species causes damage doesn’t mean that we can’t manage them with consideration for ethics and welfare.</p><img src="https://counter.theconversation.com/content/154400/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Gilchrist 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>Squirrel feeders laced with contraceptives could be used to suppress grey squirrels in the UK.Jason Gilchrist, Ecologist, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1326282020-03-02T11:53:26Z2020-03-02T11:53:26ZHow to help red squirrels fight back against invasive greys – with DNA sequencing<figure><img src="https://images.theconversation.com/files/317803/original/file-20200228-24651-lx87hb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Giedriius / shutterstock</span></span></figcaption></figure><p>The red squirrel is the UK’s only native squirrel species. Unfortunately, they are now a very rare sight across Britain and Ireland, thanks to widespread destruction of their native forests, combined with competition from the larger grey squirrel – an invasive species introduced from North America. It’s also due to the spread of diseases such as the squirrelpox virus, which causes ulcers and scabs and a painful death. </p>
<p>Although grey squirrels carry squirrelpox, they rarely suffer any symptoms. Having been exposed to the disease for a long time, they have developed an “acquired immunity” where their immune systems have learnt to fight it off. This isn’t the case for red squirrels, however, and outbreaks of the virus can kill <a href="https://rb.gy/f2ng6e">more than 80%</a> of a population. This leads to small, fragmented groups that have a higher risk of being wiped out.</p>
<p>But by studying squirrel DNA, particularly if we can work out what makes grey squirrels and some red squirrels immune to the disease, we might be able to find new ways of helping the reds survive.</p>
<p>Since 2016, one of us (Kathryn) has been researching how one isolated group of red squirrels in the town of Formby, Merseyside, has <a href="https://rebrand.ly/8ygluiy">adapted to urban life</a> alongside people. As could be the case for many isolated populations across the UK, this urban population may have genetic inbreeding caused by closely-related individuals mating with each other, which can have knock-on effects on their immune systems. The Formby population has also recently suffered from another <a href="https://rb.gy/0wjj2m">devastating outbreak</a> of squirrelpox.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/317827/original/file-20200228-24701-1g417e4.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">UK red squirrel population has fallen from 3.5m to just 150,000.</span>
<span class="attribution"><span class="source">Annabel Bligh</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>However, a scientific tool has given us new hope: genome sequencing. A genome is all the DNA in an organism and when it is “sequenced”, this gives us a complete list of everything that makes up the DNA in the chromosomes of either an individual or a whole species. A team of scientists involved in the <a href="https://www.sanger.ac.uk/science/programmes/tree-of-life">Darwin Tree of Life</a> project recently worked with Kathryn to sequence both <a href="https://rb.gy/lrdpww">red</a> and <a href="https://rb.gy/kailzw">grey</a> squirrel genomes, using pieces of spleen collected from squirrels from Formby. </p>
<p>We hope that the genomes will help us to understand the genetic basis for the grey squirrels’ immunity to squirrelpox. More importantly, they may help to explain the <a href="https://rb.gy/0r9st2">resistance</a> found in the small number of red squirrels that have survived previous outbreaks, much like with HIV in humans where a <a href="https://rb.gy/fywrwm">certain combination of genes</a> means that the virus cannot replicate well in some people. The genomes may also assist with captive breeding programmes and reintroductions or translocations in their natural habitats, by helping to establish genetically healthy red squirrel populations.</p>
<h2>How it works</h2>
<p>By comparing the genome sequences against a catalogue of known viral proteins, we can identify whether there are any new “viral insertions”. This is when a virus inserts a copy of its own genome into the DNA of a host cell and becomes inherited, which will therefore change the genome of the host, and this is what we are looking to find.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"972114794206711809"}"></div></p>
<p>We can then analyse samples collected from individual squirrels, to see whether these viruses are present or not in their genomes. This can also be explored and compared across red squirrel populations and even between different squirrel species. Depending on where the viruses are found in the genome and whether they are active – in other words, causing the host cell to make new viruses – this may impact the red squirrels’ immunity and so their susceptibility to diseases.</p>
<p>These, or similar, methods have already been used successfully in other species, for example in <a href="https://rebrand.ly/ts6b7wa">horses</a>, <a href="https://rebrand.ly/xqe9xwo">canines</a> and <a href="https://rb.gy/nnfefj">koalas</a>. They also have the potential to be used in future projects for other endangered species, as new genomes are sequenced.</p>
<p>The newly published genome sequences open up numerous exciting research opportunities, including studying population diversity, responses to diseases, and evolutionary changes due to environmental stresses. The findings can hopefully help conservationists to protect the endangered red squirrel and ensure their long-term survival in the UK.</p><img src="https://counter.theconversation.com/content/132628/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kathryn Fingland worked with the Wellcome Sanger Institute on the red and grey squirrel genome sequencing project.</span></em></p><p class="fine-print"><em><span>Rachael Tarlinton has received funding for squirrel retrovirus projects from the zebra foundation, for dog retroviruses from the royal society of veterinary surgeons trust and for koalas from the Queensland department of the environment and heritage </span></em></p><p class="fine-print"><em><span>Adam Blanchard 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>Scientists hope to learn what makes certain red squirrels able to survive squirrelpox. Kathryn Fingland, Doctoral Researcher in Wildlife Conservation & Ecology, Nottingham Trent UniversityAdam Blanchard, Assistant Professor of Computational Biology, University of NottinghamRachael Tarlinton, Associate Professor in Veterinary Virology, University of NottinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1310642020-02-26T13:49:25Z2020-02-26T13:49:25ZGrey squirrels are oblivious to threat from pine martens – giving native reds the advantage<figure><img src="https://images.theconversation.com/files/315471/original/file-20200214-10980-bhybfr.jpg?ixlib=rb-1.1.0&rect=0%2C408%2C1400%2C1270&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A European pine marten climbing a tree in the Levoča Mountains, Slovakia.</span> <span class="attribution"><span class="source">František Koneval</span>, <span class="license">Author provided</span></span></figcaption></figure><p>For as long as modern humans have been moving around the planet, we’ve been bringing animals, plants and microorganisms with us. But by introducing invasive species to ecosystems in which they did not evolve, we’ve unwittingly created problems that we now spend a great deal of effort and resources trying to rectify. </p>
<p>The North American grey squirrel is one such invasive species that was brought to Britain and Ireland during the 19th and 20th centuries. Since their introduction, grey squirrels have replaced the native red squirrel across much of its former range, mainly by <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.1216">transmitting squirrel pox to reds</a>, a deadly virus to which greys are immune. Almost all attempts to counter historic blunders with grey squirrels have been met with limited success, but it would seem that nature already has a solution.</p>
<p>Until recently, the European pine marten was a little-known member of the weasel family that lives in trees and is restricted within the British Isles to the northern reaches of Scotland and the western coast of Ireland. But in recent years, it has started to reclaim some of its former range. In parts of Ireland and Scotland where this native predator has recovered, there have been subsequent <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2017.2603">declines in grey squirrel populations</a>, allowing reds to recover. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/314445/original/file-20200210-109891-tl9js9.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">Pine martens are natural predators in Britain and Ireland. These forest specialists are returning to their old haunts after centuries of decline.</span>
<span class="attribution"><span class="source">Joshua P Twining</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>For conservationists, it almost sounds too good to be true. But why do pine martens seem to benefit native red squirrels at the expense of invasive greys?</p>
<h2>Striking fear into red squirrels</h2>
<p>Researchers sifting through masses of pine marten faeces demonstrated that pine martens eat both squirrel species, but <a href="https://www.researchgate.net/publication/257997086_A_non-invasive_approach_to_determining_pine_marten_abundance_and_predation">they tend to eat more grey than red squirrels</a>. We know <a href="https://link.springer.com/article/10.1007/s10344-019-1289-z">pine martens are opportunistic omnivores</a>, switching food throughout the year and consuming whatever is available. So it’s probably not the preferences of pine martens that lead them to eat more grey squirrels, but the availability of the squirrels themselves. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-pine-marten-is-not-every-red-squirrels-best-friend-110209">Why the pine marten is not every red squirrel's best friend</a>
</strong>
</em>
</p>
<hr>
<p>One way that prey species avoid predators is with chemical signals. Predators use scent cues to mark territories and communicate with one another, but prey animals have evolved behavioural responses to these scent cues. By eavesdropping on these chemical signals, prey species can alter their behaviour and avoid predators, increasing their chances of survival. Could the grey squirrel, an animal not native to Britain or Ireland, be naive to the risk posed by the pine marten?</p>
<p>Armed with camera traps, squirrel feeders and a solution of pine marten poo, we set out to find out if this was the case. We repeated the experiment at 20 different locations across Northern Ireland, amassing more than 8,000 minutes of squirrel footage. The results are <a href="https://royalsocietypublishing.org/doi/10.1098/rsos.191841">published in Royal Society Open Science</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/315328/original/file-20200213-10976-1fmn7dm.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">Grey squirrels didn’t register a threat when in sniffing distance of pine marten scent.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/eastern-gray-squirrel-stealing-nuts-northumberland-278173925">Will Howe/Shutterstock</a></span>
</figcaption>
</figure>
<p>Emerging red-eyed from our lab, we realised that red squirrels showed a clear fear response to pine marten scent while greys didn’t. Reds visited feeders less, fed for shorter periods of time and were more vigilant – standing on their hind legs with their head upright and tail twitching from side to side. Meanwhile, the greys continued as if nothing had changed. In some cases, grey squirrel visits to feeding stations actually increased while their vigilance decreased around pine marten scent.</p>
<p>Failing to recognise the scent of a predator as a threat leaves the grey squirrels vulnerable. In hindsight though, their behaviour isn’t surprising. Red squirrels and pine martens have shared the same evolutionary landscape for millennia – we would expect them to be aware of each other. But grey squirrels and pine martens have co-existed in the same place for a mere blink of the eye. Although the pine marten predates red and grey squirrels, they have more success in catching greys because they appear oblivious to the threat.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/314446/original/file-20200210-109896-nsus6a.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 red squirrel flags its tail and releases alarm calls after spotting a pine marten in County Fermanagh, Northern Ireland.</span>
<span class="attribution"><span class="source">Joshua P Twining</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Healthy native predator populations have wide ranging benefits to the environment they inhabit. Conservation efforts are helping <a href="https://science.sciencemag.org/content/346/6216/1517">predators to recover in parts of Europe</a>, ensuring they can restore and regulate ecosystems. If the recovery of a small weasel can have such benefits, there is immense potential for <a href="https://www.researchgate.net/publication/259652500_Status_and_Ecological_Effects_of_the_World's_Largest_Carnivores">larger predators like lynx and wolves to restore balance</a> to fragmented and degraded ecosystems.</p>
<p>Pine martens aren’t a panacea for red squirrels though. Human-led efforts will still be important in red squirrel conservation, especially because prey species can develop responses to new predators <a href="https://www.researchgate.net/publication/230620045_Behavioral_responses_of_native_prey_to_disparate_predators_Naivet_and_predator_recognition">in just a few generations</a>. Who knows whether grey squirrels will develop anti-predator behaviours.</p>
<p>But if, like the red squirrel, greys learn to recognise and avoid the pine marten, they could one day learn to survive alongside it. Useful though they may be, the pine marten – or any native predator – is more than a solution to a human-made problem. They are an essential and iconic part of the natural world. The conservation and recovery of predators may not always be easy, but in a human-dominated world, we must learn to live alongside what precious biodiversity we have left.</p><img src="https://counter.theconversation.com/content/131064/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joshua P Twining received funding from the Department of Education, Northern Ireland.
David Tosh is the Research Coordinator at National Museums Northern Ireland, he conceptualised and supervised this work. Funding for the data collection of this project was crowdfunded through a Kickstarter campaign:
<a href="https://www.kickstarter.com/projects/318099790/the-squirrel-predator-prey-project">https://www.kickstarter.com/projects/318099790/the-squirrel-predator-prey-project</a></span></em></p>Where pine martens have recovered, red squirrels have tended to benefit while grey squirrels have declined. Scientists weren’t sure why – until now.Joshua P Twining, PhD researcher in Ecology, Queen's University BelfastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1282702019-12-20T11:50:37Z2019-12-20T11:50:37ZRescued grey squirrels to be killed under new law – but Britain’s ‘invasive’ problem runs much deeper<figure><img src="https://images.theconversation.com/files/308089/original/file-20191220-11909-126w0br.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4352%2C3107&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/grey-squirrel-perched-on-fence-bird-234482893">Bruce MacQueen/Shutterstock</a></span></figcaption></figure><p>It’s <a href="https://www.gov.uk/government/news/march-2019-update-invasive-non-native-species-and-grey-squirrels">illegal in the UK for anyone to release grey squirrels into the wild</a> from December 2019. This means that wildlife rescue centres in England which previously took in, rehabilitated and released wild grey squirrels, will instead have to kill them, on both practical and ethical grounds.</p>
<p>The campaign against grey squirrels is justified by the UK government, which insists that grey squirrels <a href="https://www.gov.uk/government/news/march-2019-update-invasive-non-native-species-and-grey-squirrels">threaten native wildlife and harm the economy</a>. The cost to UK forestry is <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/ps.3458">estimated to be £10 million per year</a>, including damage to timber caused by the grey squirrel’s habit of stripping bark from trees. But that cost also includes money spent on controlling grey squirrels, and there is <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/ps.3458">no link</a> between how much is spent on controlling their numbers and reducing damage to trees. So killing grey squirrels is not necessarily money well spent.</p>
<p>There are also glaring contradictions in what is considered invasive and what needs to be controlled. There are <a href="http://meowblog.cats.org.uk/2019/07/how-many-cats-are-there-in-uk.html">11 million pet cats in the UK</a>, which kill about <a href="https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2907.2003.00017.x">27 million wild birds each year</a> and around 92 million wild prey in total.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308090/original/file-20191220-11951-49em6q.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">Domestic cats are hunting many species of wildlife to extinction.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cat-on-hunt-grass-just-before-557644864">Astrid Gast/Shutterstock</a></span>
</figcaption>
</figure>
<p>It’s often argued that killing grey squirrels is justified as they predate bird nests. They do, and so do red squirrels. But there is scant evidence that squirrels have a <a href="http://news.bbc.co.uk/earth/hi/earth_news/newsid_8448000/8448807.stm">significant impact on songbirds</a>. While domestic and feral cats decimate songbird populations, they’re unlikely to be targeted for culls any time soon.</p>
<p>Why is it acceptable for animal shelters to rescue an invasive alien species, the domestic cat, and for the public to allow them to roam free, but unacceptable for wildlife rescue centres to help and release a few grey squirrels?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/in-defence-of-the-grey-squirrel-britains-most-unpopular-invader-73983">In defence of the grey squirrel, Britain's most unpopular invader</a>
</strong>
</em>
</p>
<hr>
<h2>No game for wildlife</h2>
<p>On an even greater scale, the game bird industry <a href="http://robyorke.co.uk/wp-content/uploads/2015/05/gamebird-release.pdf">releases millions of non-native birds</a> – 35 million pheasants and six-and-a-half million red-legged partridges – into the British countryside each year, to be shot for sport. The total mass of pheasants released annually <a href="https://link.springer.com/article/10.1007/s10530-018-1795-z?wt_mc=Internal.Event.1.SEM.ArticleAuthorAssignedToIssue&utm_source=ArticleAuthorAssignedToIssue&utm_medium=email&utm_content=AA_en_06082018&ArticleAuthorAssignedToIssue_20181207">exceeds that of the entire breeding population of native birds</a>.</p>
<p>There’s evidence that pheasants <a href="https://www.gwct.org.uk/news/news/2019/january/shoots-urged-to-pay-more-attention-to-release-pen-locations,-says-new-gwct-study/">affect local plant communities</a> by increasing the area of bare ground and changing the soil chemistry. They’re also significant predators of <a href="https://www.bbc.co.uk/programmes/articles/1vLNlXWKyhrzHxLYDSGRtB0/pheasant-vs-adder-the-ancient-vendetta-between-unlikely-foes">native adders</a>, a species of major conservation concern, and <a href="http://jncc.defra.gov.uk/pdf/Article17/FCS2007-S1261-audit-Final.pdf">the extremely rare sand lizard</a>. Pheasants also cause around <a href="http://robyorke.co.uk/wp-content/uploads/2015/05/gamebird-release.pdf">a million road accidents each year</a>. When grey squirrels are singled out for strict release control on the EU hit list of <a href="http://ec.europa.eu/environment/nature/invasivealien/list/index_en.htm">Invasive Alien Species</a>, why aren’t pheasants?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308091/original/file-20191220-11924-1b4zhlv.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">Pheasants are a non-native species, but their UK population is boosted by the annual release of millions of birds for the sake of game bird shooting.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pheasant-135679211">KDamian/Shutterstock</a></span>
</figcaption>
</figure>
<p>Many of the UK’s native predators are killed to maximise the density of game birds for hunters to shoot. Snares can be legally used to kill foxes and dogs can be legally used to <a href="https://www.gov.uk/guidance/foxes-moles-and-mink-how-to-protect-your-property-from-damage">flush foxes out of cover</a> to be shot. Stoats and weasels can be <a href="https://www.gwct.org.uk/game/research/predation-control/tunnel-traps/">killed in snap traps</a>. Bird traps used under general licence <a href="https://www.gov.uk/government/news/general-licences-for-bird-control-major-changes-to-licensing-requirements">capture and kill corvids and gulls</a>. </p>
<p>Compared to the 11 million domestic cats and more than 40 million non-native game birds, there are only an <a href="https://www.theguardian.com/environment/2017/jun/02/kill-them-the-volunteer-army-plotting-to-wipe-out-britains-grey-squirrels">estimated 2.5 million grey squirrels living in the UK</a>, and <a href="https://www.telegraph.co.uk/family/life/future-grey-area-much-maligned-squirrel/">700 are taken into captivity each year</a>. The environmental impact of releasing a handful of grey squirrels – particularly in areas where red squirrels are absent – is likely negligible.</p>
<h2>Alternatives to culling</h2>
<p>Should the UK commit to the relentless killing of grey squirrels in perpetuity? Too often the default response to a “problem” animal is simply to kill it. But just about everybody accepts the impossibility of eradicating grey squirrels. The only successful local eradication happened in Anglesey in Wales, where <a href="https://www.researchgate.net/publication/312119463_Economic_damage_by_invasive_grey_squirrels_in_Europe">9,597 grey squirrels were killed at a cost of £1,019,000</a> – that’s £106.18 per squirrel, and it took 16 years.</p>
<p>I would recommend alternative methods to limit grey squirrels, and to encourage natural processes that can set a new ecological balance. These <a href="https://theconversation.com/in-defence-of-the-grey-squirrel-britains-most-unpopular-invader-73983">alternatives to trapping and shooting</a> include developing oral contraceptives to prevent grey squirrels reproducing and managing woodlands to benefit reds over greys, by planting more conifer trees and allowing pine martens to return.</p>
<p>Research continues to develop a squirrel pox vaccine that would inoculate red squirrels against the disease that greys carry. An area-specific licensing system could also be maintained, whereby rescue centre greys are only released in areas with no red squirrels and no commercial forestry concerns.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308092/original/file-20191220-11909-1q4tzyn.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">Pine martens could be an effective, natural control on grey squirrel numbers.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pine-marten-on-side-tree-717435901">DigitalNatureScotland/Shutterstock</a></span>
</figcaption>
</figure>
<p>Elsewhere, it might make little sense for wildlife rescue centres to put time, effort and money into caring for animals that, upon release, would be targeted by a cull. But the point of rescue centres isn’t principally conservation, it’s about animal welfare and well-being. Too often, when an animal is referred to as a pest or an invasive species, any concerns for their welfare go out the window.</p>
<p>In the meantime, my advice to the public is to leave injured or orphaned grey squirrels be. They are better off taking their chances in the wild.</p><img src="https://counter.theconversation.com/content/128270/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Gilchrist 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>If harm to native wildlife is the main concern then there are much bigger targets for control than grey squirrels.Jason Gilchrist, Ecologist, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1102092019-02-12T14:54:42Z2019-02-12T14:54:42ZWhy the pine marten is not every red squirrel’s best friend<figure><img src="https://images.theconversation.com/files/255061/original/file-20190122-100270-1a4iskq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The pine marten – cute but cunning.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/qFm9JV">Karen Bullock/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Pine martens are <a href="https://www.theguardian.com/environment/2018/aug/15/pine-marten-spotted-in-northumberland-for-first-time-in-90-years">returning</a> <a href="https://www.vwt.org.uk/species/pine-marten/">to areas of the UK</a> after an absence of nearly a century. Following releases in <a href="https://www.bbc.co.uk/news/uk-wales-40188235">mid-Wales</a> during 2015, reintroductions are proposed in <a href="https://www.cnp.org.uk/blog/win-or-bust-returning-red-squirrel-snowdonia">north Wales</a> and <a href="https://www.theguardian.com/environment/2018/nov/25/pine-martens-forest-of-dean-return-of-a-predator">southern England</a> for 2019.</p>
<p>The pine marten is a small native carnivore that inhabits a range of woodland habitats. It’s an excellent climber and often nests within tree cavities. This opportunistic predator has a <a href="https://www.researchgate.net/publication/327967568_The_diet_of_denning_female_European_pine_martens_Martes_martes_in_Galloway_Forest_District_South_West_Scotland_Great_Britain">varied diet</a> including fruit, eggs, songbirds and small mammals.</p>
<p>By the 1920s, pine martens were virtually extinct in the UK after centuries of persecution to protect game birds and poultry. Only a population in north-west Scotland and small numbers in northern Wales and England survived. With UK legal protection, <a href="https://www.nature.scot/plants-animals-and-fungi/mammals/land-mammals/pine-marten">their range has expanded</a> since the 1980s, increasing their encounters with the grey squirrel.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/258456/original/file-20190212-174851-12l9wb1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The introduced grey squirrel has caused native red squirrel decline in the British Isles.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cute-grey-squirrel-eating-park-455377972?src=duDGN56W9W-Sj8jK8_jJpg-1-0">Vinnikava Viktoryia/Shutterstock</a></span>
</figcaption>
</figure>
<p>Since George Monbiot penned “<a href="https://www.theguardian.com/environment/2015/jan/30/how-to-eradicate-grey-squirrels-without-firing-a-shot-pine-martens">how to eradicate grey squirrels without firing a shot</a>” in 2015, the media has courted the charismatic mammal as the <a href="https://www.theguardian.com/environment/2018/mar/07/return-of-pine-martens-could-save-britains-red-squirrels-say-scientists">saviour</a> for the UK’s embattled red squirrels.</p>
<p>The media message is simple: the return of pine martens will <a href="https://www.theguardian.com/environment/2018/mar/07/return-of-pine-martens-could-save-britains-red-squirrels-say-scientists">herald the</a> <a href="https://www.thetimes.co.uk/article/pine-martens-invited-back-to-feast-on-grey-squirrels-d26tw03vr">decline</a> or even <a href="https://www.telegraph.co.uk/science/2018/03/07/predatory-pine-martens-could-save-red-squirrel/">eradication</a> of grey squirrels, which, since their arrival from North America in 1876, have caused regional <a href="https://theconversation.com/grey-squirrels-are-bad-for-the-british-countryside-full-stop-75470">extinctions of the native red squirrel</a>. That’s because pine martens supposedly prefer eating greys, while leaving reds alone.</p>
<p>The optimism around pine martens in the UK originated from research in <a href="https://link.springer.com/article/10.1007/s10531-014-0632-7">Ireland</a> and <a href="https://www.researchgate.net/publication/323615222_The_enemy_of_my_enemy_is_my_friend_Native_pine_marten_recovery_reverses_the_decline_of_the_red_squirrel_by_suppressing_grey_squirrel_populations">Scotland</a>. In Scotland, scientists studied forests containing pine martens, red squirrels and grey squirrels. The more pine martens they recorded using a woodland area, the more likely they were to find red squirrels and the less likely grey squirrels were to be there. Like earlier <a href="https://theconversation.com/resurgent-pine-martens-could-be-good-news-for-red-squirrels-46051">Irish studies</a>, this suggested that pine martens suppress grey squirrel populations to the overall benefit of red squirrels. </p>
<p>However, that’s not quite the whole story. There’s a desire in the media to find <a href="https://www.sciencedirect.com/science/article/abs/pii/S0006320712001462">heroes and villains in nature</a> which simplifies the situation and obscures the potential impact of a returning predator on British wildlife and livestock. Sadly, ecology and conservation are rarely simple and the restoration of pine martens will not always follow a script.</p>
<h2>Red squirrels on the menu?</h2>
<p>The <a href="https://www.researchgate.net/publication/323615222_The_enemy_of_my_enemy_is_my_friend_Native_pine_marten_recovery_reverses_the_decline_of_the_red_squirrel_by_suppressing_grey_squirrel_populations%20are%20careful">Scottish pine marten researchers</a> make clear that pine martens sometimes eat red squirrels. In a small number of other <a href="https://www.researchgate.net/publication/280294387_A_long-term_study_of_the_winter_food_niche_of_the_pine_marten_Martes_martes_in_northern_boreal_Finland">studies</a> conducted <a href="http://rcin.org.pl/dlibra/docmetadata?id=11728">elsewhere in Europe</a>, reds were in fact a significant seasonal component of pine marten diet – up to 53% in one case.</p>
<p>It’s therefore incorrect to suggest, <a href="https://pine-marten-recovery-project.org.uk/our-work/faqs">as some conservation groups have</a>, that dietary studies show pine martens very rarely eat red squirrels. The reality is that predation rates reflect the relative abundance of red squirrels to other prey, encounter rates and local habitat characteristics.</p>
<p>Why grey squirrels have declined in the presence of pine martens <a href="https://theconversation.com/resurgent-pine-martens-could-be-good-news-for-red-squirrels-46051">remains uncertain</a>. The impact of martens on greys may vary geographically and it’s unwise to simply extrapolate the findings from <a href="https://www.researchgate.net/publication/323615222_The_enemy_of_my_enemy_is_my_friend_Native_pine_marten_recovery_reverses_the_decline_of_the_red_squirrel_by_suppressing_grey_squirrel_populations">Scotland</a> and <a href="https://link.springer.com/article/10.1007/s10531-014-0632-7">Ireland</a> to the rest of the British Isles without a note of caution. Suggesting the pine marten is <a href="https://www.theguardian.com/environment/2018/mar/07/return-of-pine-martens-could-save-britains-red-squirrels-say-scientists">the best long-term solution</a> for grey squirrel control in England is premature and requires more research to confirm.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=597&fit=crop&dpr=1 600w, https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=597&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=597&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=750&fit=crop&dpr=1 754w, https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=750&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/255057/original/file-20190122-100288-15n3phc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=750&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An owl sanctuary in Northern Ireland had an unwelcome visit from a pine marten.</span>
<span class="attribution"><a class="source" href="https://www.facebook.com/worldofowls1/">World of Owls</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Pine martens have been absent from much of England for <a href="https://www.mammal.org.uk/species-hub/full-species-hub/discover-mammals/species-pine-marten/">around 100 years</a>, a period of significant agricultural and urban change. Landscapes have altered dramatically and many potential prey species have <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/lapwing/population-trends/">regionally declined</a>. Pine marten predation upon these could therefore prove to be locally significant.</p>
<p>This should not be a barrier to reintroducing pine martens. Instead, it reinforces the need for informed discussions with all interest groups likely to be affected. We must acknowledge that as a last resort, <a href="https://community.rspb.org.uk/ourwork/b/martinharper/posts/tough-choices-a-follow-up-comment-about-values-and-motivations">lethal control of predators</a> may be necessary to conserve rare species such as some ground nesting birds.</p>
<p>As the pine marten becomes more common in the UK and Ireland, inevitably there will be scenarios where <a href="https://www.nature.scot/plants-animals-and-fungi/mammals/land-mammals/pine-marten">lethal intervention is unavoidable</a>. A pine marten predating a seabird colony was shot in 2018 under licence to protect an internationally important breeding population.</p>
<p>Measures to prevent predation of poultry or game birds are frequently recommended where pine marten restoration is occurring. These include the installation of electric fencing, cutting back branches overhanging pens and ensuring that wire netting has no holes martens could get through.</p>
<p>While these management recommendations are useful, many people may find it difficult to implement them. As a result, any negative impacts of a returning arboreal predator will <a href="https://www.longfordleader.ie/video/home/234811/video-longford-man-devastated-following-pine-martens-attack-on-his-hens-and-partridges.html">fall heavily</a> upon a handful of poultry owners.</p>
<p>The return of the pine marten <a href="https://www.bbc.co.uk/news/uk-scotland-highlands-islands-44532518">may also complicate</a> the conservation or reintroduction of other species. Although the location and other details are confidential, there were concerns that a pine marten was adversely affecting a red squirrel conservation programme after an individual was found to be regularly visiting release enclosures.</p>
<p>As pine martens naturally spread from Scotland into northern England, <a href="https://www.europeansquirrelinitiative.org/wp-content/uploads/2018/06/ESI-Pine-Marten-A-Revised-Position-.pdf">adaptive and measured responses</a> will be needed to responsibly manage their return. An approach to conservation that’s media-friendly but built on limited evidence rarely works, and certainly won’t in pine marten restoration.</p><img src="https://counter.theconversation.com/content/110209/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We should welcome a native predators’ return across the British Isles, while at the same time being honest about the implications.Craig Shuttleworth, Honorary Visiting Research Fellow, Bangor UniversityMatt Hayward, Associate professor, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/820242017-08-15T14:09:37Z2017-08-15T14:09:37ZWhy red squirrels are thriving in one corner of Merseyside<figure><img src="https://images.theconversation.com/files/182085/original/file-20170815-29205-5bcb20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="source">Phil Kieran / shutterstock</span></span></figcaption></figure><p>By 2050, <a href="http://ow.ly/MpUZ30e73sA">two thirds</a> of the world’s population will live in an urban area. Until recently, we knew little about how wild animals were coping with the growth of all those towns and cities. The field of urban wildlife ecology has since emerged to fill this gap.</p>
<p>Urban ecologists have found some species, like Britain’s <a href="http://ow.ly/XkQb30e73IM">hedgehogs</a>, have struggled to cope. But other species, often called “synurbic”, have proven themselves very adaptable and, in some cases, they can actually live at <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2011.00887.x/abstract">higher densities</a> in cities. </p>
<p>One species capable of modern urban living is the red squirrel. Understanding how they behave in towns and cities, a topic that is relatively unexplored, could help their long-term conservation.</p>
<p>Red squirrels are found in cities right across mainland Europe, for example in <a href="http://ow.ly/iaMw30e73WQ">Finland</a>, <a href="http://www.scoiattologrigio.org/scoiattoli%20-%20european%20red%20squirrels%20urban%20park.pdf">France</a>, and <a href="http://ow.ly/20Jp30e746U">Poland</a>. It is likely they were once also found in many UK towns too. However, Britain’s native squirrel is now a very rare sight, thanks to decades of habitat loss and the introduction of the larger and more competitive grey squirrel from North America.</p>
<h2>A red stronghold</h2>
<p>But one town where the reds haven’t disappeared is Formby, in Merseyside, the study site for my PhD researching the urban ecology of red squirrels. Formby is one of few red squirrel strongholds in England and one of the only remaining urban areas where they can be found at all. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"519839175932379136"}"></div></p>
<p>Red squirrels can easily be spotted in gardens throughout the town. Local residents are passionate about protecting their unusual wildlife, with many of them providing supplemental food and volunteering locally with <a href="https://www.wildlifetrusts.org/news/2017/02/24/vital-volunteers-needed-save-our-last-red-squirrels">conservation organisations</a>. These organisations manage the extensive woodland to the west of the town, where they supply additional food themselves, and employ dedicated “squirrel officers” who help maintain “<a href="https://www.lancswt.org.uk/redsquirrels">grey squirrel-free</a>” habitats.</p>
<p>In addition to the woodland, the town itself contains ideal habitat, with hedgerows and trees lining the roads and gardens, which provide corridors for the squirrels to move through. Urban areas also typically have fewer natural predators, such as buzzards.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182090/original/file-20170815-28964-6ywrrk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&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 woods near Formby are famous for their red squirrels.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/fotofrivolity08/13611318394/">Ellie</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Unfortunately, invasive grey squirrels like all these things too and, given the chance, they would colonise the town and displace the reds. However, a combination of grey squirrel control (including protection from their advances on one side by the sea), supplemental feeding, suitable urban green spaces, and careful monitoring by volunteers and rangers have meant that the reds have clung on in Formby, despite greys replacing them elsewhere in the UK. </p>
<p>The longer-term strategy is to manage the area in favour of the reds. This could involve, for example, planting trees which the reds can easily exploit but the greys are less able to, like native conifers and small-seeded broadleaved trees such as birch or ash. Greys instead prefer large-seeded broadleaves, such as oak and beech.</p>
<h2>Urban hazards</h2>
<p>However, there are downsides to living alongside people. For instance, several studies have flagged <a href="http://ow.ly/C6OZ30e74me">road traffic</a> as the biggest cause of squirrel mortality. Despite fewer natural predators, there are higher numbers of pets, such as <a href="http://onlinelibrary.wiley.com/doi/10.1017/S0952836902000134/abstract">cats</a> and dogs, that can injure and even kill squirrels. In addition, some of the trees in the town may be gradually lost as residents landscape their gardens, further fragmenting the remaining habitat.</p>
<p>Even the widespread supplemental feeding could have hidden negative consequences. In Formby, well-meaning residents provide lots of peanuts: one of the squirrels’ favourite foods. Unfortunately, peanuts are low in calcium and alone do not give the required nutrition that a squirrel needs. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182092/original/file-20170815-28398-1ayvmsu.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">Chomping on a peanut provided by a well-meaning local.</span>
<span class="attribution"><span class="source">Kat Fingland</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>If feeders are not cleaned thoroughly and regularly, this could also contribute to another outbreak of <a href="http://ow.ly/SiNI30e74wz">squirrelpox virus</a> or other diseases. This suggests that residents, who are enthusiastic about feeding the squirrels (and should continue to do so), perhaps need to be provided with more information, such as on what to supply for a varied diet.</p>
<h2>Urban management as a conservation tool</h2>
<p>Much of the research and conservation of red squirrels in the UK is carried out in more rural areas, such as Kielder Forest in Cumbria, often along the interface with the invasive grey squirrel. However, managing urban sites for the benefit of the native reds could be a useful alternative conservation tool, through making the most of the benefits of living alongside people. </p>
<p>For example, local volunteers could act as a free and dedicated workforce for conserving and monitoring the red squirrels, as is the case in Formby. This could be employed in the nearby towns, or even elsewhere in Britain near squirrel strongholds, to hopefully encourage the reds to disperse and reoccupy areas as they become free from greys. This is currently occurring in Wales, with reds crossing over from the island of <a href="https://www.theguardian.com/environment/2016/oct/13/red-squirrels-wales-protected-military-style-strategy-ogwen-valley">Anglesey</a> onto the mainland as rangers remove greys from the area around nearby Bangor.</p>
<p>An urban management plan could also create the opportunity to develop more green spaces and wildlife-friendly gardens. This would benefit all of the local biodiversity, not only squirrels, as well as the people.</p>
<p>This is what my research aims to explore over the next few years: how have red squirrels adapted to urban life, and how do the associated resources and risks affect their ecology. By understanding this, we can hopefully develop a strategy to better protect this charming native species.</p><img src="https://counter.theconversation.com/content/82024/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kathryn Fingland is working closely with the Lancashire Wildlife Trust and National Trust to conduct her PhD research in Formby.</span></em></p>Formby is one of the only remaining urban areas in England where red squirrels can be found at all.Kathryn Fingland, Doctoral Researcher in Wildlife Conservation & Ecology, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/754702017-04-06T14:01:41Z2017-04-06T14:01:41ZGrey squirrels are bad for the British countryside – full stop<figure><img src="https://images.theconversation.com/files/163326/original/image-20170330-4578-1ftx14x.jpg?ixlib=rb-1.1.0&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/113551735@N04/21418461706/">Tom D/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>According to some animal rights groups the grey squirrel is a <a href="http://www.huffingtonpost.co.uk/andrew-tyler/red-fur-good-grey-fur-bad_b_10144572.html">victim of circumstance</a>. They say it has been made a <a href="https://www.animalaid.org.uk/please-defend-grey-squirrels/">scapegoat</a> for regional red squirrel population extinctions and claim that loss of the reds is caused entirely <a href="http://www.thejournal.co.uk/news/north-east-news/father-son-champion-grey-squirrels-4468630">coincidentally by habitat change</a>. They suggest the <a href="http://www.grey-squirrel.org.uk/victimising_grey_squirrels_2.pdf">true facts are being hidden</a> and scientific research being <a href="http://www.thepetitionsite.com/en-gb/723/774/674/stop-the-european-union-squirrel-cull/">intentionally misinterpreted</a>. </p>
<p>If so, then this conspiracy must extend to <a href="http://www.telegraph.co.uk/news/earth/wildlife/8331195/What-is-the-law-on-killing-squirrels.html">British legal provisions</a> and <a href="https://www.theguardian.com/environment/2015/sep/25/eu-clamps-down-on-grey-squirrels-and-other-invasive-wildlife">EU directives</a> both listing the grey squirrel as an invader to be controlled, right? </p>
<p>Well, no – put this argument to the test and you’ll see that the facts actually do stack up against the grey squirrel. The reality is that, while the grey squirrel is an important part of <a href="https://cals.arizona.edu/research/redsquirrel/res_pdf/Other%20Squirrel%20and%20Sky%20Island%20Publications/Mamm%20Spec%20Sciurus%20carolinensis%2094.pdf">North American forest ecosystems</a>, since being brought to Europe by the <a href="https://www.theguardian.com/environment/2012/sep/05/red-grey-squirrels-cornwall">Victorians</a> in 1876, the animal has had severe <a href="https://www.woodlandtrust.org.uk/mediafile/100258230/Squirrel-position-statement.pdf">ecological and economic impacts</a> on British woodlands. </p>
<p>Acrobatic and entertaining they may be, but the charge sheet against the grey squirrel is based on hundreds of peer-reviewed research papers. There really is no <a href="https://theconversation.com/in-defence-of-the-grey-squirrel-britains-most-unpopular-invader-73983">defence</a> for it. </p>
<h2>Greys vs red in Europe</h2>
<p>Today there are <a href="http://www.telegraph.co.uk/news/earth/wildlife/10705527/History-of-grey-squirrels-in-UK.html">approximately 2.5m</a> grey squirrels in Britain, but less than <a href="https://www.forestry.gov.uk/forestry/redsquirrel">140,000 reds</a>. Grey squirrels <a href="http://www.snh.org.uk/pdfs/publications/naturallyscottish/redsquirrel.pdf">out-compete</a> native reds for food and space. They also dig up and <a href="https://www.jstor.org/stable/4602061?seq=1#page_scan_tab_contents">consume seed</a> that red squirrels have buried as a winter store. This behaviour reduces red squirrel skeletal growth rates and adult size, and greatly depresses <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2004.00791.x/abstract">juvenile survival rates</a> too. </p>
<p>In addition, greys harbour infections – including <a href="http://www.macs.hw.ac.uk/%7Eawhite/White_Hystrix2016.pdf">squirrel pox</a>, which can devastate red squirrel populations. They <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914897/">elevate local viral and nematode infection rates</a>, and bring in new parasites, such as <a href="https://air.unimi.it/retrieve/handle/2434/232973/302558/phd_unimi_r08996.pdf">Strongyloides robustus</a>, which are picked up by red squirrels.</p>
<p>Occasionally a healthy red squirrel is found with squirrel pox antibodies – some researchers have suggested that this is evidence of them <a href="https://www.theguardian.com/environment/2013/nov/22/red-squirrels-poxvirus-resistance">evolving resistance</a> to the pox. Unfortunately, 63% of red squirrels dying from pox have also been found to have this <a href="http://squirrelweb.co.uk/2015/06/22/new-book-on-red-squirrel-conservation-published/">antibody response present</a> and there is no evidence that these antibodies confer immunity. Even if they did, research has also shown that antibodies are <a href="http://www.italian-journal-of-mammalogy.it/article/view/10126">gone within 18 months</a> and, irrespective of any resistance, red populations would be replaced by grey via competition anyway.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/163328/original/image-20170330-4555-i3vuw7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Squirrel pox.</span>
<span class="attribution"><span class="source">Sarah McNeil</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Woodland damage</h2>
<p>Grey squirrels also <a href="http://www.sciencedirect.com/science/article/pii/S0378112716300421">damage and kill forest trees</a> making it impossible for foresters to grow high-grade hardwood. This means such material is imported instead, bringing with it the risk of <a href="https://www.theguardian.com/environment/2016/oct/23/british-trees-threat-imported-timber-disease-china">new tree pests and pathogens</a>.</p>
<p>Tree damage is most frequently seen on the branches and trunks of oak, beech and maple; <a href="https://www.forestry.gov.uk/fr/infd-7rlgm2">bark is stripped</a> by squirrels eager to consume the <a href="https://www.forestry.gov.uk/pdf/fcpn004.pdf/$FILE/fcpn004.pdf">the sap underneath</a>. Tree stems break or die following stripping, which in turn leads to changes in the <a href="https://www.forestry.gov.uk/pdf/fcpn004.pdf/$FILE/fcpn004.pdf">structure and species composition</a> of high canopy in amenity woodlands.</p>
<p>Even songbirds are affected by grey squirrels. A <a href="http://news.cision.com/kendalls/r/predation-of-woodland-songbirds--grey-squirrels-have-a-case-to-answer,c9224977">recent study gave evidence</a> of negative association between woodland songbird fledging rates and presence of grey squirrels – though it must be noted that this was not observed annually and only seen on some of the sites studied. Earlier studies didn’t find evidence to indicate greys <a href="http://news.bbc.co.uk/earth/hi/earth_news/newsid_8448000/8448807.stm">affect bird population</a>, but also didn’t exclude the possibility – even for bird species whose population is increasing overall. </p>
<p>Other animals may be affected by greys too: there has been some suggestion that squirrels compete with <a href="http://link.springer.com/chapter/10.1007%2F978-94-011-2362-4_11">dormice for hazel nuts</a>, though more research is needed to <a href="http://www.europeansquirrelinitiative.org/wp-content/uploads/2016/12/web-ESI-newsletter-issue-29-lowres.pdf">confirm the true impact</a>.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/163329/original/image-20170330-4557-1auejbp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Stripped tree bark.</span>
<span class="attribution"><span class="source">Craig Shuttleworth</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Controlling greys</h2>
<p>The Wildlife Trust has recently <a href="https://www.theguardian.com/environment/2017/feb/24/red-squirrels-5000-volunteers-sought-to-save-species-and-help-kill-invasive-greys">started to recruit</a> 5,000 volunteers to monitor and control grey squirrel populations. However, a look beyond the headlines will reveal thousands of people are already legally <a href="http://www.smallholder.co.uk/news/15080927.Grey_squirrels_best_controlled_using_a_variety_of_techniques/?ref=mrb&lp=13">trapping and shooting</a> greys across the country to control their numbers. <a href="http://www.northernredsquirrels.org.uk/nrs-groups/">Volunteer groups</a> cull 6,000 grey squirrels per year in the north of England, for example. Even in areas where reds are absent, locals control grey squirrels to protect woodlands or <a href="https://www.gov.uk/pest-control-on-your-property">prevent damage to property</a>. This is not some dramatic new approach by the Wildlife Trust, but is simply reinforcing an established national movement.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/163327/original/image-20170330-4551-x7l8rh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Red and grey meet on the battleground.</span>
<span class="attribution"><span class="source">David Bailey</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The eradication of greys from the <a href="http://link.springer.com/article/10.1007/s10530-014-0671-8">Welsh isle of Anglesey</a> saw red squirrel numbers increase from 40 to 700 and there are other <a href="http://www.italian-journal-of-mammalogy.it/article/view/9988">examples</a> of grey control halting or reversing red squirrel decline. Research has also demonstrated that red squirrels do not prefer <a href="https://www.researchgate.net/publication/279174227_Red_squirrel_population_dynamics_in_different_habitats">conifer to broadleaved</a> habitat and are just as happy in either.</p>
<p>Future control may involve giving the squirrels <a href="https://www.ncbi.nlm.nih.gov/pubmed/22182332">contraception</a>, but will almost certainly not rely solely on this because of logistical barriers. The pine marten may assist in some landscapes too: <a href="http://link.springer.com/article/10.1007/s10531-014-0632-7">one Irish study</a> found a strong negative correlation between pine martens and greys in the woodlands studied. However, the use of trapping and shooting will inevitably continue as part of an <a href="http://www.rfs.org.uk/news/2017/3/grey-squirrel-fertility-control-funding-top-priority-says-rfs/">integrated national approach</a>.</p>
<p>And so the grey squirrel stands guilty as charged. Their presence has decimated the British countryside since they were introduced from North America, and if we do not continue to control the species, the future for red squirrels and woodland ecosystems will be bleak.</p><img src="https://counter.theconversation.com/content/75470/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig Shuttleworth is an independent advisor to the European Squirrel Initiative and is on the management board of the EU LIFE14 NAT/UK/000467 invasive species project. He is a Director of Red Squirrels Trust Wales which receives funding from Welsh Government to study viral infections in squirrel species including squirrelpox. </span></em></p>Grey squirrels are wreaking havoc on UK woodlands.Craig Shuttleworth, Honorary Visiting Research Fellow, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/739832017-03-08T00:10:57Z2017-03-08T00:10:57ZIn defence of the grey squirrel, Britain’s most unpopular invader<figure><img src="https://images.theconversation.com/files/159869/original/image-20170308-14966-kvh4eq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Jason Gilchrist / jasongilchrist.co.uk</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Furry, fast, occasionally chubby. Small, whiskered, bushy tailed. An expert climber. A nut eater. And grey.</p>
<p>For those in the UK, everything was going great until that last trait. You were probably thinking “cute” and “cuddly”, and feeling positive about this mystery mammal. Until you discover it is the grey and not the red squirrel.</p>
<p>Grey squirrels are a contradiction. They have all the characteristics of animals that people tend to love, and yet they are actively persecuted by humankind. BBC presenter Chris Packham calls them Britain’s “most unpopular non-native invader” – and one of their unflattering nicknames is the “<a href="http://www.dailymail.co.uk/news/article-390805/Damn-tree-rats.html">tree rat</a>”. </p>
<p>The Wildlife Trust has recently announced plans to recruit <a href="https://www.theguardian.com/environment/2017/feb/24/red-squirrels-5000-volunteers-sought-to-save-species-and-help-kill-invasive-greys">an army of 5,000 volunteers</a> to monitor their endangered native relative, the red squirrel – and kill the greys.</p>
<h2>Cute but criminal</h2>
<p>So why such a bad press for grey squirrels? Firstly, they ain’t from around here: greys were deliberately introduced from North America in the late 19th century as an exotic addition to country estates. They soon spread across the UK, however, and today the invaders are the dominant squirrel across almost all of England and Wales and much of Scotland and Ireland.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"835126115362619398"}"></div></p>
<p>But hostility towards invasive animals can’t explain the grey squirrel’s unpopularity – as other non-native species don’t get the same negative attention. The UK’s <a href="http://www.mammal.org.uk/species-hub/uk-mammal-list/">naturalised mammals</a> include the brown hare, the edible dormouse, and sika deer. Even the much-loved rabbit is a <a href="http://www.telegraph.co.uk/news/earth/wildlife/6574709/Mouse-and-rabbits-among-non-native-species.html">Roman import</a>.</p>
<p>Instead, grey squirrels are disliked, by foresters due to the damage that they inflict upon trees, and more generally because of the harm they cause to their native relatives, red squirrels. Studies have shown that <a href="https://link.springer.com/article/10.1007/s00265-001-0446-y">greys can outcompete reds</a> – the two species do not directly fight for resources, it is just that the greys are better at gathering the nuts and berries that both live off. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=354&fit=crop&dpr=1 600w, https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=354&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=354&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=445&fit=crop&dpr=1 754w, https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=445&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/159587/original/image-20170306-20749-82nt7q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=445&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Red squirrel: across the UK greys now outnumber these reds by around 17 to 1.</span>
<span class="attribution"><span class="source">Jason Gilchrist/www.jasongilchrist.co.uk</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Grey squirrels are also unknowingly the carrier of a disease, squirrel pox, to which they are immune, but sadly the red is not. For red squirrels, the pox means painful scabs, ulcers and <a href="http://www.northernredsquirrels.org.uk/squirrels/squirrel-pox-virus/">almost certain death</a> (although some are finally <a href="http://www.forestry.gov.uk/pdf/ukrsg_advice_note_E1.pdf/$FILE/ukrsg_advice_note_E1.pdf">developing resistance</a>). The pox itself may actually be the chief “evil immigrant” in this eco-relationship, with the grey squirrel simply moving into vacant habitat following an epidemic among local red squirrels.</p>
<h2>Ethics and welfare of killing</h2>
<p>Whatever the true ecological relationship between red and grey squirrel, the human species has for many years been waging war on the unfortunate invader. Human nature is such that, the moment we label a species as a “pest”, the welfare of individual animals is often ignored. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=367&fit=crop&dpr=1 600w, https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=367&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=367&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=461&fit=crop&dpr=1 754w, https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=461&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/159856/original/image-20170307-14934-qg84ga.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=461&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Watch out! The grey squirrel is under attack.</span>
<span class="attribution"><span class="source">Jason Gilchrist/www.jasongilchrist.co.uk</span></span>
</figcaption>
</figure>
<p>The grey squirrel is not so different from the red. How would we feel if we were to trap, poison and shoot the red squirrel? Greys did not come over here of their own accord and did not ask to be introduced. Neither do they have any control over the pox that they carry. They do what they do; which is to be grey squirrels. In response, what we do, is kill them by the tens of thousands, year after year. The killing is “humane” – but how free of pain and suffering is it for the squirrels? We poison them. We trap them. We shoot them. We bludgeon them to death.</p>
<p>How many dead greys is a live red worth? The success of this sustained massacre is debatable. Nobody seriously believes that the grey squirrel could be exterminated in the UK. A report by Stephen Harris and colleagues at the University of Bristol concluded that culling greys to save reds is <a href="https://www.onekind.scot/wp-content/uploads/0811_grey_squirrel_populations.pdf">neither viable nor economic</a>. Harris has instead suggested that we should move the reds to <a href="http://news.bbc.co.uk/1/hi/sci/tech/5238462.stm">protected islands</a> and let nature take its course on the mainland. We could <a href="http://www.telegraph.co.uk/news/earth/wildlife/11301638/Millions-of-pounds-of-public-money-to-pay-for-grey-squirrel-cull.html">save ourselves a lot of time, money and effort</a> by not persecuting grey squirrels.</p>
<h2>We don’t need to kill to conserve</h2>
<p>I don’t want Britain to lose its native red squirrel. But neither do I take any joy from the thought of the tens of thousands of culled grey squirrels and the <a href="https://www.theguardian.com/environment/2017/feb/24/red-squirrels-5000-volunteers-sought-to-save-species-and-help-kill-invasive-greys">infinite number that we will have to kill</a> if current plans are to continue in perpetuity. </p>
<p>We need to show a bit more respect to this highly successful species and there are alternative options to culling. We could start by managing forests to favour conifers (which reds prefer) over deciduous trees (the grey’s favourite).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/159585/original/image-20170306-20739-1199mrs.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">Pine marten: the smaller and more agile red squirrel evolved alongside this predator and may be better at escaping it.</span>
<span class="attribution"><span class="source">Peter Cairns/scotlandbigpicture.com</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The resurgence of the native pine marten could also swing the balance in favour of reds over greys. A conservation success story in itself, these ferret-like predators were recently spotted in England for the first time in more than a century. In areas of Ireland where pine martens are thriving, grey squirrels have <a href="https://www.theguardian.com/environment/2015/jan/30/how-to-eradicate-grey-squirrels-without-firing-a-shot-pine-martens">almost disappeared</a>, allowing reds to reestablish themselves.</p>
<p>The occurrence of <a href="http://www.telegraph.co.uk/news/earth/wildlife/11516777/Squirrel-Nutkin-fights-back-in-battle-against-grey-rivals.html">pox-resistance</a> within some red squirrel populations is also a reason for hope for red over grey. Last but not least is the development of <a href="https://www.theguardian.com/environment/shortcuts/2017/feb/26/grey-squirrels-prince-charles-nutella?CMP=twt_a-environment_b-gdneco">an oral contraceptive for grey squirrels</a> together with plans to bait them using Nutella.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/159874/original/image-20170308-14932-n1fsc6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&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 humane way to reduce grey squirrel numbers.</span>
<span class="attribution"><span class="source">Jason Gilchrist / jasongilchrist.co.uk</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Some would describe the grey squirrel as criminal. Others would describe the way they are treated by humans as criminal. Ultimately, we don’t necessarily need to kill to conserve.</p><img src="https://counter.theconversation.com/content/73983/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Gilchrist 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>Grey squirrels have lots of attractive characteristics, yet they are actively persecuted by humankind.Jason Gilchrist, Ecologist, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/460512015-08-27T05:37:30Z2015-08-27T05:37:30ZResurgent pine martens could be good news for red squirrels<figure><img src="https://images.theconversation.com/files/92804/original/image-20150824-17760-1811mrl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-301498676/stock-photo-pine-marten-on-log-in-dense-green-foliage-pine-marten-european-pine-marten-martes-martes.html?src=pp-same_artist-297853694-YQHED2pyi-p6PF3VBf8KVA-4">www.shutterstock.com</a></span></figcaption></figure><p>A pine marten has been <a href="http://www.theguardian.com/environment/2015/jul/15/pine-marten-spotted-in-england-for-the-first-time-in-over-100-years">spotted in England recently</a>, the first in more than 100 years. The reemergence of Britain’s second-rarest mammal, a cat-sized relative of badgers and weasels, is a great story in itself. But it may have another upside, as pine martens could be bad news for one of the UK’s least popular animals: the invasive grey squirrel.</p>
<p>Unlike pine martens, grey squirrels are not native to Britain. These North American “aliens” were first introduced in the 1870s and soon made themselves at home. In the UK they are considered an invasive species – their “<a href="http://www.forestry.gov.uk/pdf/fcpn004.pdf/$FILE/fcpn004.pdf">bark-stripping</a>” harms the growth of new woodlands and has a big economic cost. </p>
<p>Grey squirrels’ success has also been to the <a href="http://www.grey-squirrel.org.uk/reds.php">detriment</a> of the native red squirrel. Greys do not kill reds directly, but they do spread <a href="http://www.northernredsquirrels.org.uk/squirrels/squirrel-pox-virus/">squirrel pox</a>, a virus that causes distinctive ulcers on the reds’ eyes and nose, leading to death within a week. Grey squirrels themselves are unaffected – they’ve developed immunity. </p>
<p>Things are looking pretty dire for the UK’s red squirrels. Competition, disease and habitat loss mean that, if current <a href="http://www.rsne.org.uk/grey-squirrel-control">grey squirrel control</a> efforts were to stop, red squirrels would become extinct in Britain.</p>
<p>I’m interested in how pine martens fit into this struggle. Habitat loss, hunting for fur and predator control by game keepers meant they became practically extinct in England and Wales. However in Scotland and Ireland they are making a comeback – and where they are returning, grey squirrels are disappearing.</p>
<h2>Why Ireland has red squirrels</h2>
<p>The impact in Ireland has been particularly notable. A <a href="http://link.springer.com/article/10.1007%2Fs10531-014-0632-7">four-year study</a> I published in 2014 found pine marten recovery in the Irish midlands was linked to such a significant decline in grey squirrel numbers that the once beleaguered red squirrel population was able to recolonise its former range, including woodlands which had been dominated by greys for more than 30 years. </p>
<p>The study provided the first evidence for what foresters and gamekeepers had been saying for years – where pine martens had returned to healthy numbers, grey squirrels had all but disappeared. But in areas with few or no pine martens, grey squirrels persisted at “<a href="http://link.springer.com/article/10.1007%2Fs10531-014-0632-7">invasive</a>” levels. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92790/original/image-20150824-17787-1uq6oy9.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>
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<span class="caption">This guy ought to be grateful.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=89EJJWE6gd5JUngun1S2gA&searchterm=red%20squirrel&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=306584732">www.shutterstock.com</a></span>
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<p>Red squirrels on the other hand have coexisted with pine martens throughout much of Europe for tens of thousands of years. The two species evolved together. While pine martens will very occasionally eat red squirrels, they don’t seem to have a negative impact on population numbers. In fact, in the Irish study, the areas that red squirrels had recolonised naturally were exclusively those with healthy pine marten populations.</p>
<h2>Do pine martens eat grey squirrels?</h2>
<p>We do know that more pine martens in an area means fewer grey squirrels, but we don’t yet know if this is down to direct predation. It does happen though: the first evidence of a pine marten preying on the American grey squirrel was <a href="http://link.springer.com/article/10.1007/s10344-013-0771-2">also recorded in Ireland</a> in 2013, and we are now looking for evidence of this in the Scottish borders too. </p>
<p>Grey squirrels are larger and less agile than red squirrels and typically spend more of their time on the ground, making them an easier prey. However, having a healthy native predator around could also affect grey squirrels in various other ways: they might simply learn to avoid known pine marten areas, or they might spend less time on the ground foraging, leading to reduced fitness. Grey squirrels might even be suffering physiological effects such as <a href="http://beheco.oxfordjournals.org/content/early/2011/10/10/beheco.arr169.full">stress-induced reproductive problems</a>.</p>
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<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=89EJJWE6gd5JUngun1S2gA&searchterm=grey%20squirrel&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=302518733">www.shutterstock.com</a></span>
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<h2>Pine martens as pest eradicators?</h2>
<p>Ultimately we need to determine whether the pine marten could act as a natural biological control for the grey squirrel in Britain and Ireland.</p>
<p>That’s why I’m now looking at Scotland, where there have been reports of <a href="http://www.telegraph.co.uk/news/earth/wildlife/10998856/Red-squirrels-are-fighting-back-against-the-greys-experts-claim.html">grey squirrel declines</a> after pine marten recolonisation since the early 2000s. I want to know if the two processes are linked. </p>
<p>There are several subtle but potentially important differences between pine marten populations in the two countries that I’ll need to take into account – Scottish pine martens can feast on field voles, for instance, a rich food source that isn’t found in Ireland.</p>
<p>Mass reintroduction of pine martens may be implausible but the creatures are moving south through Scotland and are literally just a few miles from the English border, so the process of natural recolonisation in England is almost underway. The recent sightings in Shropshire may even mean the remnant Welsh population is spreading into England too. It is important to remember pine martens are very slow breeders however, and it will take the recovering population quite some time to reach levels healthy enough to potentially impact on grey squirrel populations. </p>
<p>Predators are a vital part of a healthy ecosystem and predator prey interactions have an important function. What’s happening in Ireland and potentially Britain with squirrels and pine martens is a great example of how restoring natural predators can reduce the damage caused by invasive species. We are currently living in an unnaturally predator-poor environment, and it’s possible this has allowed some introduced species to reach “invasive” levels, which has ultimately wreaked havoc on our ecosystem. </p>
<p>Interaction between pine martens and squirrels is fascinating from a scientific point of view and we still have lots to learn. But you don’t have to be an ecologist to appreciate the value of promoting one of Britain’s most beautiful native species in order to preserve another.</p><img src="https://counter.theconversation.com/content/46051/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Sheehy receives funding from The Irish Research Council, Marie Curie, Forestry Commission Scotland</span></em></p>Grey squirrels hate these reclusive, cat-sized predators.Emma Sheehy, Postdoctoral Research Fellow in Ecology, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.