tag:theconversation.com,2011:/au/topics/torpor-14594/articlesTorpor – The Conversation2022-01-27T19:01:09Ztag:theconversation.com,2011:article/1756102022-01-27T19:01:09Z2022-01-27T19:01:09ZGut microbes help hibernating ground squirrels emerge strong and healthy in spring<figure><img src="https://images.theconversation.com/files/442826/original/file-20220126-27-13smcdk.jpg?ixlib=rb-1.1.0&rect=63%2C369%2C3142%2C1959&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When not hibernating, ground squirrels need to feast to store energy.</span> <span class="attribution"><a class="source" href="https://doi.org/10.1126/science.abh2950">Robert Streiffer</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Ground squirrels spend the end of summer gorging on food, preparing for hibernation. They need to store a lot of energy as fat, which becomes their primary fuel source underground in their hibernation burrows all winter long.</p>
<p>While hibernating, ground squirrels enter <a href="https://doi.org/10.1111/brv.12137">a state called torpor</a>. Their metabolism drops to as low as just 1% of summer levels and their body temperature can <a href="https://doi.org/10.1152/physrev.00008.2003">plummet to close to freezing</a>. Torpor greatly reduces how much energy the animal needs to stay alive until springtime.</p>
<p>That long fast comes with a downside: no new input of protein, which is crucial to maintain the body’s tissues and organs. This is a particular problem for muscles. In people, long periods of inactivity, like prolonged bed rest, <a href="https://doi.org/10.1186/s13728-015-0036-7">lead to muscle wasting</a>. But muscle wasting is minimal in hibernating animals. Despite as much as six to nine months of inactivity and no protein intake, they preserve muscle mass and performance remarkably well – a very handy adaptation that helps ensure a successful breeding season come spring.</p>
<p>How do hibernators pull this off? It’s been <a href="https://doi.org/10.1086/650471">a real head-scratcher</a> <a href="https://doi.org/10.1152/ajpregu.1991.261.5.R1214">for hibernation biologists for decades</a>. <a href="https://scholar.google.com/citations?user=TUVZbtcAAAAJ&hl=en&oi=ao">Our research</a> <a href="https://scholar.google.com/citations?user=zuJyGe8AAAAJ&hl=en&oi=ao">team tackled</a> this question by investigating how hibernating animals might be getting a major assist <a href="https://doi.org/10.1126/science.abh2950">from the microbes that live in their guts</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="small mammal curled into a ball, nestled in wood chips" src="https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442827/original/file-20220126-23-o570i5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The 13-lined ground squirrel shows minimal signs of muscle wasting, even after hibernating for up to six months.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1126/science.abh2950">Robert Streiffer</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>A nitrogen-recycling system</h2>
<p>We knew from previous research that a hibernator’s <a href="https://doi.org/10.1016/j.cbpa.2020.110875">gastrointestinal system undergoes dramatic changes</a> in its structure and function from summer feeding to winter fasting. And it’s not only the animals who are fasting all winter long – their gut microbes are, too. Along with our microbiology collaborators, we figured out that <a href="https://doi.org/10.1146/annurev-nutr-071816-064740">winter fasting changes the gut microbiome</a> quite a bit.</p>
<p>And then we wondered … could gut microbes play a functional role in the process of hibernation itself? Could certain bacteria help keep muscle and other tissues working when the mostly immobile animals aren’t eating?</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="brown cow munching grass" src="https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=671&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=671&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=671&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=843&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=843&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443024/original/file-20220127-6424-ql553k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=843&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Microbes in their guts help ruminants, including cows, hold on to the nitrogen they need to build proteins.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/brown-cow-royalty-free-image/1219160750">Lemanieh/ iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>Biologists had previously identified a clever trick in ruminant animals, such as cattle, that helps them survive times when protein intake in the diet is low or protein needs are especially high, such as during pregnancy. A process <a href="https://doi.org/10.1079/NRR200498">called urea nitrogen salvage</a> allows the animal to recoup nitrogen – a critical ingredient for building protein – that would otherwise be excreted in urine as the waste product urea. Instead, the urea’s nitrogen is retained in the body and used to make amino acids, the building blocks of proteins.</p>
<p>This salvage operation depends on the chemical breakdown of urea molecules to release their nitrogen. But here’s the kicker: Chemical breakdown of urea requires urease, an enzyme that animals do not produce. So how does a cow, for instance, get that nitrogen out of urea?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="ball and stick model of a chemical structure" src="https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443025/original/file-20220127-16-1kqqp1u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A model of the urea molecule, with two nitrogen atoms (in blue) along with a carbon (gray), an oxygen (red) and four hydrogen (white) atoms.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/urea-molecule-royalty-free-illustration/147217473">LAGUNA DESIGN/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<p>It turns out certain microbes that are normal residents of animals’ guts can do just that. They make the urease enzyme and use it to chemically split urea molecules, freeing up the nitrogen, which becomes part of ammonia molecules. Microbes then absorb ammonia and use it to make new protein for themselves.</p>
<p>Peculiarities of the ruminant digestive system allow those animals to benefit greatly from this process. But for other animals – like hibernators and us – it was less clear whether and how the urea nitrogen could make its way into the animals’ bodies to support protein synthesis.</p>
<p>This was our challenge as scientists: Could we demonstrate urea nitrogen recycling in hibernators and show that it is particularly helpful to them the longer they fast?</p>
<h2>Our experimental game plan</h2>
<p>Using the 13-lined ground squirrel, <a href="https://doi.org/10.1126/science.abh2950">we designed experiments to investigate</a> key steps in urea nitrogen salvage.</p>
<p>First, we injected into the squirrel’s bloodstream urea molecules in which the two nitrogen atoms were replaced by a heavier form of nitrogen that naturally occurs only in tiny amounts in the body.</p>
<p>We were able to follow these heavier nitrogen atoms as the injected urea moved from the blood into the gut, then as microbial urease broke down the urea into its component parts, and finally into the squirrels’ tissue metabolites and proteins. Wherever we saw higher levels of the heavier form of nitrogen, we knew that urea was the source of the nitrogen, and therefore gut microbes had to be responsible for getting the urea nitrogen back into the animals’ bodies.</p>
<p>To confirm that the microbes were doing the nitrogen recycling, we compared squirrels that had normal gut microbiomes to squirrels that didn’t. We treated some animals with antibiotics to reduce gut microbes at three times of the year: summer; early winter, when they were one month into fasting and hibernation; and late winter, whwithen they were four months into fasting and hibernation.</p>
<p>In squirrels with normal microbiomes, we saw evidence of urea nitrogen salvage at each step of the process that we tested. But squirrels with depleted microbiomes displayed minimal urea nitrogen salvage. Our observations confirmed that this process was indeed dependent on the gut microbes’ ability to break down urea and liberate its nitrogen in the hibernators’ guts. Hibernators’ liver and muscle tissue incorporated the most urea nitrogen during late winter – that is, the longer they’d been hibernating and without food.</p>
<p>We also found that the ground squirrels contribute to this remarkable symbiosis. During hibernation, their gut cells increase production of proteins called urea transporters. These molecules are lodged in intestinal cell membranes and shepherd urea from the blood into the gut where the microbes that contain urease are found. This assist means that what little urea the animal makes during hibernation has an easier route to the gut.</p>
<p>Finally, we found that it wasn’t just squirrels who benefited from this process. The microbes too were using the urea nitrogen to build their own proteins, showing that urea nitrogen salvage provides both parties with this important molecular building block during the long winter fast.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Fal-vhNgxvs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Every few weeks, hibernating squirrels arouse temporarily, as seen in this time-lapse video. They don’t eat or drink or leave the burrow, but the short increase in body temperature lets enzymes like urease do their jobs.</span></figcaption>
</figure>
<h2>Could this kind of symbiosis help humans?</h2>
<p>This example of hibernator-microbe symbiosis has potential clinical applications. For example, undernourishment, which affects millions of people globally, leads to a progressive decline in muscle mass and compromises health. Sarcopenia, which is muscle wasting that is a natural part of aging, impairs mobility and makes people more susceptible to injury. A detailed understanding of how the hibernator nitrogen salvage system is most effective when the risk of tissue loss and muscle wasting is greatest could lead to new therapeutics to help people in similar situations.</p>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.]</p>
<p>Another potential application is in human spaceflight, during which crew members experience <a href="https://doi.org/10.33549/physiolres.934550">high rates of muscle atrophy</a> because of a microgravity-induced suppression of muscle protein synthesis. Even the extensive exercise regime that astronauts undertake to offset this is insufficient. A microbiome-based countermeasure that facilitates muscle protein synthesis similar to the process we have observed in hibernators may be worth investigating.</p>
<p>These applications, though theoretically possible, are a long way from delivery. But studies in the 1990s demonstrated that humans are capable of <a href="https://doi.org/10.1097/01.mco.0000196142.72985.d3">recycling small amounts of urea nitrogen with the help of their gut microbes</a>. So the necessary machinery is in place – it just needs to be optimized.</p><img src="https://counter.theconversation.com/content/175610/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hannah V. Carey received funding from the U.S. National Science Foundation for this work.</span></em></p><p class="fine-print"><em><span>Matthew Regan receives funding from the Natural Sciences and Engineering Research Council of Canada and the Canadian Space Agency.</span></em></p>Months not eating or moving don’t result in muscle wasting and loss of function for animals that hibernate. New research found gut microbes help their hosts hold onto and use nitrogen to build proteins.Hannah V. Carey, Professor Emeritus of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-MadisonMatthew Regan, Assistant Professor of Biological Sciences, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1464092020-12-29T20:40:16Z2020-12-29T20:40:16ZTorpor: a neat survival trick once thought rare in Australian animals is actually widespread<figure><img src="https://images.theconversation.com/files/360952/original/file-20200930-22-1iez5gv.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6016%2C4016&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Life is hard for small animals in the wild, but they have many solutions to the challenges of their environment. One of the most fascinating of these strategies is torpor. Not, to be confused with sleep or Sunday afternoon lethargy, torpor is a complex response to the costs of living. </p>
<p>To enter torpor, an animal decreases its metabolism, reducing its energy requirements. A torpid animal will often be curled in a tight ball in its nest and look like it’s sleeping.</p>
<p>Once thought to occur only in birds and mammals in the Northern Hemisphere where winters are more pronounced, we now know torpor is <a href="https://publications.rzsnsw.org.au/doi/abs/10.7882/AZ.2010.009">widespread</a> in small Australian mammals, and has also been observed in many small Australian bird species. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An echidna in the bush." src="https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=377&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=377&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=377&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=474&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=474&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360944/original/file-20200930-18-qcv9gh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=474&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Echidnas use torpor to save energy.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/animal-response-to-a-bushfire-is-astounding-these-are-the-tricks-they-use-to-survive-129327">Animal response to a bushfire is astounding. These are the tricks they use to survive</a>
</strong>
</em>
</p>
<hr>
<h2>Masters of metabolism</h2>
<p>Birds and mammals are endotherms and can maintain a high and constant body temperature independent of the environmental temperature, thanks to their high metabolic rate. This allows them to be active across a wide range of environments. </p>
<p>The downside? This high metabolic rate requires a lot of food to fuel it. By reducing the metabolism in a very controlled manner and entering torpor, an animal can live on less energy. </p>
<p>With a lower metabolic rate, the animal’s body temperature decreases — sometimes by as much as 30°C. How low it goes can depend on the extent of the metabolic reduction and the temperature of animal’s immediate environment. The reduced body temperature further lowers the metabolic rate.</p>
<h2>Slowing down to survive</h2>
<p>Torpor is an extremely effective survival strategy for small endotherms. For example, small mammals have been observed <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2015.0134">using torpor after bushfires</a>. </p>
<p>Take the brown antechinus, for example. When other animals have fled, this 30g marsupial hides in refuges, waits out the fire, then uses torpor to cope with reduced food availability until local vegetation and invertebrate populations recover. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A brown antechinus on a tree." src="https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=421&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=421&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=421&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=530&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=530&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360942/original/file-20200930-14-167f4a6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=530&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 brown antechinus uses torpor to cope with reduced food availability after bushfire.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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</figure>
<p>Many pregnant and lactating bats and <a href="https://academic.oup.com/icb/article/54/3/516/2797887">marsupials</a>, and even the <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0006070">echidna</a>, synchronise torpor with reproduction to cope with the energetic costs of mating, pregnancy or lactation. </p>
<p>There are two main types of torpor: daily torpor and hibernation. </p>
<h2>Daily torpor</h2>
<p>Animals that use daily torpor can do so for approximately 3-6 hours a day as needed.</p>
<p>Daily torpor is common in, but not exclusive to, endotherms living in arid areas, such as the fat-tailed dunnart. This species is a carnivorous marsupial and has a <a href="https://link.springer.com/article/10.1007/s00114-007-0293-4">diet</a> of insects and other invertebrates, which may be in short supply in winter. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A fat-tailed dunnart." src="https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=378&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=378&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=378&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=475&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=475&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360948/original/file-20200930-22-h9ene3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=475&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When finding enough food is difficult, the fat-tailed dunnart uses torpor.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Weighing approximately 12 grams as adults, the fat-tailed dunnart may need to eat its body weight in food each day. When finding enough food is difficult, it uses torpor; foraging in the early part of the night then entering torpor in the early morning. Fat-tailed dunnarts reduce their metabolic rate, and subsequently their body temperature, from 35 °C to approximately 15°C, or the temperature of their underground nest.</p>
<h2>Hibernation</h2>
<p>Animals that hibernate lower their metabolic rate further and have longer torpor bouts than those that use daily torpor. An example of an Australian hibernator is the eastern pygmy possum, a 40g marsupial found in south eastern Australia that hibernates regularly, decreasing its body temperature from approximately 35 °C to as low as 5°C. </p>
<p>When active, this species can <a href="https://link.springer.com/article/10.1007/s00114-007-0274-7?con=&dom=pscau&src=syndication">survive for less than half a day</a> on 1g of fat, but when hibernating, it can survive for two weeks. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359702/original/file-20200924-13-wk5n4g.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A torpid eastern pygmy possum. Note the curled posture.</span>
<span class="attribution"><span class="source">Photo credit: Chris Wacker</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>If it weren’t for the periodic increases in metabolic rate and body temperature, a hibernating pygmy possum could live for well over three months on 1g of fat. However, the exact purpose of these periodic arousals is unknown. </p>
<p>The metabolic rate during pygmy possum hibernation is just 2% of the minimum metabolic rate endotherms at a normal body temperature need to live. This baseline metabolism is called basal metabolic rate. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An American black bear" src="https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360945/original/file-20200930-22-1weulat.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">Black bears can’t hibernate with a lower body temperature.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Compare this with a well-known hibernator, the <a href="https://science.sciencemag.org/content/331/6019/906.abstract?casa_token=AZwPQmQ0w9QAAAAA:zDNkBqJWQo5VURWXpZ1tavfjXYVPcJxwPahYWRpOva9kCJaXp5EY4y3Jo3JNmNS4fHLtMpLaB3hTP7s">American black bear</a>.</p>
<p>At approximately 120kg, its metabolic rate during hibernation decreases to 25% of the basal metabolic rate, and the body temperature decreases from approximately 37°C to 30 °C. Black bears can’t hibernate with a lower body temperature, perhaps because it would take them a very long time to reduce it, and then cost them too much energy to rewarm at the end of hibernation.</p>
<h2>Can humans do it?</h2>
<p>The question people often ask about torpor, is “can humans do it?” Interestingly, some small <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/evan.21588?casa_token=u8I8ehxWRq0AAAAA%3ACiJacjM8jdzhJdC74EKZHznxZOXPqiR5t5LegoIvkg2FeMc6DGglQ5E3p3W0u2YoCpPmwdK9Aml20NM">primates have been observed using torpor</a>. While it is technically possible to induce torpor in humans chemically, torpor is a very complex physiological process, and there are many aspects of it scientists still don’t fully understand. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A gray mouse lemur in Madagascar." src="https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360947/original/file-20200930-22-152k6b1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The grey mouse lemur in Madagascar is among the primates that uses torpor.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Coping with climate change</h2>
<p>Australia’s wildlife have evolved strategies to cope with life in an often-harsh environment affected by multiple year-long droughts, landscape-altering floods, and widespread bushfires.</p>
<p>Climate change is predicted to increase the duration, frequency and severity of these events, and in conjunction with landscape clearing, animals are facing new environmental and resource challenges. </p>
<p>While animals that use flexible, daily torpor may be well-suited to cope during these times, at least in the short term, hibernators that depend on long winters are most at risk. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/summer-bushfires-how-are-the-plant-and-animal-survivors-6-months-on-we-mapped-their-recovery-142551">Summer bushfires: how are the plant and animal survivors 6 months on? We mapped their recovery</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/146409/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Wacker has received funding through Australian Geographic for a study in Kosciuszko National Park.
</span></em></p>Once thought to occur only in birds and mammals in the Northern Hemisphere, due to the more pronounced winters, we now know torpor is widespread in small Australian mammals.Chris Wacker, Postdoctoral Research Fellow - School of Environmental and Rural Science, University of New EnglandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1464842020-10-20T01:46:22Z2020-10-20T01:46:22ZHard to spot, but worth looking out for: 8 surprising tawny frogmouth facts<figure><img src="https://images.theconversation.com/files/361266/original/file-20201002-24-wkstt2.jpg?ixlib=rb-1.1.0&rect=0%2C35%2C7856%2C5194&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The <a href="https://australian.museum/learn/animals/birds/tawny-frogmouth/?gclid=CjwKCAjw_NX7BRA1EiwA2dpg0sqSuSf8dkALMbiMCj657VwrMiusEVI7FDOUNL4IWhyXVpIjBOKXkxoCfqoQAvD_BwE">tawny frogmouth</a> is one of Australia’s most-loved birds. In fact, it was first runner-up in the Guardian/BirdLife Australia <a href="https://www.theguardian.com/environment/2019/nov/15/black-throated-finch-wins-2019-bird-of-the-year-as-tawny-frogmouth-comes-second">bird of the year</a> poll (behind the endangered black-throated finch).</p>
<p>Tawny frogmouths are found throughout Australia, including cities and towns, and population numbers are healthy. We’re now in the breeding season – which runs from August to December – so you may have been lucky enough to see some pairs with chicks recently.</p>
<p>Here are eight fascinating things about tawny frogmouths that you might not know.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C1125%2C894&q=45&auto=format&w=1000&fit=clip"><img alt="A Tawny Frogmouth and its chick." src="https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C1125%2C894&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358771/original/file-20200918-18-97cfqa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">You might have been lucky enough to see a tawny frogmouth chick recently.</span>
<span class="attribution"><span class="source">Carol Smith</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-australian-birds-can-teach-us-about-choosing-a-partner-and-making-it-last-125734">What Australian birds can teach us about choosing a partner and making it last</a>
</strong>
</em>
</p>
<hr>
<h2>1. They are excellent parents</h2>
<p>Tawny frogmouths are excellent parents. Both males and females share in building the nest and incubating the eggs, generally one to three. The eggs take 30 days to hatch, with the male incubating during the day and both sexes taking turns during the night. </p>
<p>Once hatched, both parents are very involved in feeding the fledglings. A young bird’s wings take about 25 to 35 days to develop enough strength for flight (a process known as “fledging”).</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1310872114178662401"}"></div></p>
<h2>2. They mate for life</h2>
<p>Tawny frogmouths pair for life. Breeding pairs spend a great deal of time roosting together and the male often gently strokes the female with his beak. Some researchers <a href="https://theconversation.com/laughs-cries-and-deception-birds-emotional-lives-are-just-as-complicated-as-ours-69471">report</a> seeing tawny frogmouths appear to “grieve” when their partner dies.</p>
<p>For example, renowned bird behaviour expert Gisela Kaplan <a href="https://www.afr.com/life-and-luxury/arts-and-culture/the-inner-lives-of-birds--on-show-in-mornington-20161118-gssuc9">tells of</a> rearing a male tawny frogmouth on her property then releasing it to the wild. It found a female mate and raised nestlings. One day, the female was run over on the highway; Kaplan recognised its markings. </p>
<p>She found the male “whimpering” on a nearby post. Kaplan reportedly said: “It sounds like a baby crying. It affects you to listen to it.” According to Kaplan, the male stayed there for four days and nights, and did not eat or drink.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pair of Tawny Frogmouths in a tree." src="https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361251/original/file-20201002-16-4opbvx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Breeding pairs spend a great deal of time roosting together.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>3. They’re not owls</h2>
<p>Although tawny frogmouths are often referred to as owls, they are not. But they do resemble owls with their large eyes, soft plumage and camouflage patterns, because both owls and frogmouths hunt at night. This phenomenon (where two species develop the same attributes, despite not being closely related) is called “convergent evolution”.</p>
<p>Unlike owls, tawny frogmouths do not have powerful feet and talons with which to capture prey. Instead, they prefer to catch prey with their beaks. Their soft, wide, forward-facing beaks are designed for catching insects. They will also feed on small birds, mammals and reptiles.</p>
<h2>4. They are masters of disguise</h2>
<p>Tawny frogmouths are extremely well camouflaged and when staying statue-still on a tree branch they appear to be part of the tree itself. They often choose to perch near a broken tree branch and thrust their head at angle, further mimicking a tree branch.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tawny frogmouth sits still on a branch." src="https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361244/original/file-20201002-13-17aa6o5.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">Tawny frogmouths are extremely well camouflaged and when staying statue-still on a tree branch they appear to be part of the tree itself.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>5. They make strange noises</h2>
<p>Tawny frogmouths are quite vocal at night and have a range of calls from deep grunting to soft “wooing”. When threatened, they make a loud hissing sound. Their vocalisations have also variously been described as purring, screaming and crying.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Ohu9mPFMXEk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>6. They can survive extremes</h2>
<p>In colder regions of Australia, tawny frogmouths are able to survive the winter months by going into torpor for a few hours. In this state, an animal slows its heart rate and metabolism and lowers its body temperature to conserve energy. </p>
<p>On very hot summer days tawny frogmouths will produce mucus in their mouths which cools the air they breathe in, thereby cooling their whole body. </p>
<h2>7. They need old trees</h2>
<p>It’s not that uncommon to see tawny frogmouths dead on the road; they often flit across the road chasing insects at night and can be hit by cars. </p>
<p>Tawny frogmouth populations are holding relatively steady, but there is a shortage of old trees for nesting. They especially like trees with old branches as they mimic old branches and stick out like sore thumbs on young branches. </p>
<p>When one NSW council chopped down a suburban tree that a tawny frogmouth pair had reportedly used for years as a nesting site, one of the birds was <a href="https://au.news.yahoo.com/owl-tawny-frogmouth-central-coast-council-hides-on-wood-chipper-as-last-tall-tree-on-street-felled-101536900.html?guccounter=1">photographed</a> sitting on a nearby woodchipper — a poignant image. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1186824740029132801"}"></div></p>
<h2>8. They’re not good at building nests.</h2>
<p>Tawny frogmouths are pretty slack when it comes to nest building. They simply dump twigs and leaves in a pile and that is it. Chicks and eggs have even fallen out of the nest when parents are swapping brooding duties.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three tawny frogmouths in a tree" src="https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361249/original/file-20201002-19-cfyrw5.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">Tawny frogmouths especially like trees with old branches.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/laughs-cries-and-deception-birds-emotional-lives-are-just-as-complicated-as-ours-69471">Laughs, cries and deception: birds' emotional lives are just as complicated as ours</a>
</strong>
</em>
</p>
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<img src="https://counter.theconversation.com/content/146484/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Les Christidis was Senior Curator of Ornithology at the Museum Victoria from 1987 to 1996.</span></em></p>Breeding pairs spend a great deal of time roosting together and the male often gently strokes the female with his beak.Les Christidis, Professor, Southern Cross UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1263982020-01-27T12:19:14Z2020-01-27T12:19:14ZWhat is white-nose syndrome in bats?<figure><img src="https://images.theconversation.com/files/310004/original/file-20200114-151876-zaicwr.jpeg?ixlib=rb-1.1.0&rect=0%2C5%2C1266%2C846&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dr. Winifred Frick examines a bat for white-nose syndrome.</span> <span class="attribution"><span class="source">Alan Hicks</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<p>What is white-nose syndrome in bats? – Minti F., age 13, Boston, Massachusetts</p>
<hr>
<p>Scientists count bats in the winter to make sure their populations are doing okay. They look in caves and abandoned mines where bats hibernate when it is too cold to hunt for insects to eat.</p>
<p>About 10 years ago, during their annual winter bat counts, scientists noticed that bats in caves in New York state were dying. The bats that were still alive had a white fuzzy growth on their muzzles and wings. Scientists didn’t know what it was and named it <a href="https://www.whitenosesyndrome.org/static-page/what-is-white-nose-syndrome">white-nose syndrome</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310016/original/file-20200114-151876-ezxm9e.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">Little brown bats with white-nose syndrome.</span>
<span class="attribution"><span class="source">Alan Hicks</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Now we know a lot more about white-nose syndrome, a disease that kills bats when they hibernate. I am <a href="http://frick.eeb.ucsc.edu/">a scientist who studies bats</a> to learn more about how to protect them. </p>
<h2>A fungus that infects hibernating bats</h2>
<p>The white-nose syndrome disease is caused by a fungus that grows on bats’ skin when they are trying to survive winter by hibernating in cold, dark subterranean habitats like mines and caves. <a href="http://www.batcon.org/why-bats/bats-are/bats-are-important">Bats are mammals</a> like you. But unlike people, they have a special ability to “go cold” to save energy when there isn’t anything to eat. This is called torpor.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=795&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=795&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=795&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=999&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=999&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310003/original/file-20200114-151825-14pvdwj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=999&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hibernating tri-colored bat.</span>
<span class="attribution"><span class="source">Winifred Frick</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The fungus that causes this disease can live on the walls of caves and mines. It grows best in cold temperatures and infects bats when their immune system, which fights infection, isn’t as active. </p>
<p>Bats have skin on their wings, muzzles and a membrane that connects between their tail and hind legs. The fungus eats into those skin tissues, causing lesions. The infection causes the bats to wake up from their energy-saving torpor. Bats can’t survive for long in the middle of winter without food, and they starve to death.</p>
<p>Bats started dying by the thousands in the winter of 2006-2007, sounding the alarm that something was seriously wrong. Some bat species are more vulnerable to the disease, like the northern long-eared bat, the little brown bat and the tri-colored bat. </p>
<p>We estimate that millions of bats across North America have died as the fungus has spread. Bats need our help. In the past 10 years, many wildlife biologists have worked hard to help bats survive. There are no easy solutions, but a lot of scientific research is underway to discover how we can protect bats.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em>
<em>Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/126398/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Winifred Frick works for Bat Conservation International, a non-profit organization dedicated to protecting bat populations around the world.</span></em></p>Researchers are puzzled by a fungus that is killing millions of bats.Winifred Frick, Associate Research Professor of Ecology and Evolutionary Biology, University of California, Santa CruzLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1304542020-01-24T13:39:15Z2020-01-24T13:39:15ZIf it’s below 40 degrees in South Florida, the forecast calls for falling iguanas<figure><img src="https://images.theconversation.com/files/311728/original/file-20200124-81395-1atcoom.jpg?ixlib=rb-1.1.0&rect=61%2C129%2C4155%2C2884&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Beware cold-stunned 'chicken of the trees.'</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Falling-Iguanas/1c9c5a58f8f24f6cb0a28552f256aa94/4/0">AP Photo/Wilfredo Lee</a></span></figcaption></figure><p><em>As <a href="https://www.palmbeachpost.com/news/20200121/palm-beach-county-prepare-yourself-for-arctic-blast-wednesday-morning">temperatures were dipping</a> this week, the National Weather Service <a href="https://twitter.com/NWSMiami/status/1219691736412246016">issued freeze warnings</a> for much of Florida and Georgia, adding a warning in South Florida for “falling iguanas.” University of Florida wildlife ecologist <a href="https://scholar.google.com/citations?user=bygBLL8AAAAJ&hl=en&oi=ao">Frank Mazzotti</a> explains the physiology of cold iguanas and why many people in Florida aren’t shedding tears for the iguana-cicles lying around the region.</em> </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1219691736412246016"}"></div></p>
<h2>What happens to iguanas when temps drop?</h2>
<p>When temperatures fall into the 40s and 30s, green iguanas become cold-stunned. They <a href="https://www.springer.com/us/book/9780412403507">enter what’s called</a> <a href="https://doi.org/10.1016/B978-0-12-409548-9.11167-4">a state of torpor</a>. Their breathing slows down and so does their metabolism.</p>
<p>Used to more balmy conditions, this is how tropical reptiles protect themselves from cold temperatures. Torpor is an involuntary response, and the animals trade torpor’s benefit of conserving heat in cold conditions for an increased risk of being snagged by a predator.</p>
<p>Torpor causes green iguanas to lose muscle control, and since they live in trees, they fall out of trees. A several pound iguana falling on your head would definitely get your attention.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1219951774779498496"}"></div></p>
<h2>What should you do if you see a dazed iguana?</h2>
<p>If you witness falling iguanas, your best course of action is to do nothing. If the animal warms up quickly, it will recover on its own. If cold temperatures are prolonged, the iguana may die.</p>
<p>But please do not try to “rescue” any iguanas. Native to Mexico, Central and South America and some Caribbean islands, <a href="https://myfwc.com/wildlifehabitats/profiles/reptiles/green-iguana/">green iguanas are an invasive species</a> in the southern United States and you cannot legally set them free here. The iguanas you spot in South Florida are descendants of animals brought here to be sold as pets.</p>
<p>If you want to get involved when you see a fallen iguana, a better course of action is to eat it. In their native range they are prized as <a href="https://www.sun-sentinel.com/features/fl-reg-eating-iguana-south-florida-invasive-20180627-story.html">delicious food items</a> and are called chicken of the trees or bamboo chicken.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311729/original/file-20200124-81403-txewew.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">In South Florida, animal control includes exotic lizard management.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/captiva-island-exotic-lizard-management-program-iguana-news-photo/1189372908">Jeffrey Greenberg/Education Images/Universal Images Group via Getty Images</a></span>
</figcaption>
</figure>
<h2>Why are some officials in Florida happy to see fewer iguanas?</h2>
<p>Officials believe green iguanas are rapidly increasing in numbers and <a href="https://www.eddmaps.org/distribution/viewmap.cfm?sub=12119">expanding in range</a>, though there are no concrete counts for how many live in Florida today.</p>
<p>For a long time, <a href="https://www.ucpress.edu/book/9780520238541/iguanas">green iguanas</a> flew below the radar of management agencies. <a href="https://doi.org/10.1073/pnas.1115226109">Unlike Burmese pythons</a>, for example, which eat mammals and birds, green iguanas did not pose an obvious threat to ecological resources. Any <a href="http://edis.ifas.ufl.edu/in528">damage they did</a> was confined to backyards where they readily consume landscape plants, burrow into seawalls and sidewalks and poop prodigiously.</p>
<p>But with more green iguanas on the loose, they are now commonly found on water management structures such as levees and pump stations where they actively burrow, <a href="https://www.jstor.org/stable/1445983">especially nesting females</a>. These infrastructure facilities control water levels in South Florida and keep neighborhoods dry while providing a water supply for both agriculture and residences.</p>
<p>Iguana-caused damage is not minor. For example, the City of West Palm Beach recently paid <a href="https://www.palmbeachpost.com/news/20200120/iguanas-not-just-nuisance-these-lizards-contributed-to-18m-repair-bill-in-west-palm">US$1.8 million to repair</a> a weir that was partially damaged by burrowing iguanas and to armor the low dam against further damage.</p>
<p>Removing invasive iguanas is now necessary to protect Florida’s ability to manage its water. So a cold snap that eliminates some of the iguana population might actually be good news in some quarters.</p>
<p>[ <em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/130454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frank Mazzotti receives funding from the South Florida Water Management District, the Florida Fish and Wildlife Conservation Commission, and the Department of the Interior. </span></em></p>Green iguanas are an invasive species that seem to be spreading and proliferating in Florida. Used to warmer temps, they switch into torpor mode when the mercury drops.Frank Mazzotti, Professor, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1087342019-01-18T11:40:11Z2019-01-18T11:40:11ZIs winter miserable for wildlife?<figure><img src="https://images.theconversation.com/files/254403/original/file-20190117-32804-apjf4.jpg?ixlib=rb-1.1.0&rect=81%2C25%2C2643%2C1821&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Yes, I am a bit chilly, why?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/snow-covered-gray-squirrel-41186005">tim elliott/Shutterstock.com</a></span></figcaption></figure><p>While the weather outside may indeed get frightful this winter, a parka, knit hat, wool socks, insulated boots and maybe a roaring fire make things bearable for people who live in cold climates. But what about all the wildlife out there? Won’t they be freezing?</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254404/original/file-20190117-32810-4nw5ku.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">Pets are often suited up with protection from the cold.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cute-little-terrier-wearing-snow-shoes-171263291">Photology1971/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Anyone who’s walked their dog when temperatures are frigid knows that canines will shiver and favor a cold paw – which partly explains <a href="https://www.forbes.com/sites/pamdanziger/2018/10/18/the-pet-retail-market-is-hot-and-getting-hotter-by-the-day/#33d070d7ecdd">the boom in</a> the <a href="http://www.petbusiness.com/November-2018/Dog-Apparel-Trends/">pet clothing industry</a>. But chipmunks and cardinals don’t get fashionable coats or booties. </p>
<p>In fact, wildlife can succumb to frostbite and hypothermia, just like people and pets. In the northern United States, the unfurred tails of opossums are a common casualty of cold exposure. Every so often an unusual cold snap in Florida <a href="https://www.nytimes.com/2018/01/04/us/iguana-florida-cold-weather.html">results in iguanas</a> <a href="https://www.washingtonpost.com/news/animalia/wp/2018/01/04/iguanas-are-falling-out-of-trees-in-florida-because-its-so-cold-please-dont-pick-them-up/">falling from trees</a> and <a href="https://miami.cbslocal.com/2010/12/10/florida-manatee-deaths-reach-record-high-due-to-cold-weather/">manatees dying</a> <a href="https://weather.com/science/nature/news/2018-02-05-manatee-deaths-florida-cold-water-stress-syndrome">from cold stress</a>.</p>
<p>Avoiding the cold is important for preserving life or limb (or, in the opossum’s case, tail) and the opportunity to reproduce. These biological imperatives mean that wildlife must be able to feel cold, in order to try to avoid the damaging effects of its extremes. Animal species have their own equivalent to what human beings experience as that unpleasant biting mixed with pins-and-needles sensation that urges us to warm up soon or suffer the consequences. In fact, the nervous system mechanisms for <a href="https://doi.org/10.1113/jphysiol.2014.280446">sensing a range of temperatures</a> are pretty much the <a href="https://doi.org/10.1242/jeb.024430">same among all vertebrates</a>. </p>
<p>One winter challenge for warm-blooded animals, or <a href="https://www.khanacademy.org/science/biology/principles-of-physiology/metabolism-and-thermoregulation/a/endotherms-ectotherms">endotherms</a>, as they’re scientifically known, is to maintain their internal body temperature in cold conditions. Interestingly though, temperature-sensing thresholds can vary depending on physiology. For instance, a cold-blooded – that is, ectothermic – frog will sense cold starting at a lower temperature compared to a mouse. Recent research shows that hibernating mammals, like the thirteen-lined ground squirrel, <a href="https://doi.org/10.1016/j.celrep.2017.11.083">don’t sense the cold until lower temperatures</a> than endotherms that don’t hibernate.</p>
<p>So animals know when it’s cold, just at varying temperatures. When the mercury plummets, are wildlife suffering or just going with the icy flow?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254376/original/file-20190117-32831-1h30sus.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some animals find a protected spot to wait out the worst of it, like this chipmunk.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/riebart/4653744013">Michael Himbeault</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>One solution: Slow down and check out</h2>
<p>Many cold-climate endotherms exhibit torpor: a state of decreased activity. They look like they are sleeping. Because animals capable of torpor alternate between internally regulating their body temperature and allowing the environment to influence it, scientists consider them “heterotherms.” During harsh conditions, this flexibility offers the advantage of a lower body temperature – remarkably in some species, even below the 32 degrees Fahrenheit freezing point – that is not compatible with many physiologic functions. The result is a lower metabolic rate, and thus lower energy and food demand. Hibernation is a prolonged version of torpor.</p>
<p>Torpor has energy conservation benefits for smaller-bodied wildlife in particular – think bats, songbirds and rodents. They naturally lose heat faster because the surface area of their body is large compared to their overall size. To maintain their body temperature within normal range, they must expend more energy compared to a larger-bodied animal. This is especially true for <a href="https://doi.org/10.1007/s00442-017-3923-3">birds who maintain higher average body temperatures</a> compared to mammals.</p>
<p>Unfortunately, torpor is not a perfect solution to surviving frigid conditions since it comes with trade-offs, such as a higher risk of becoming another animal’s lunch.</p>
<h2>Adaptations that help</h2>
<p>Unsurprisingly, animals have evolved other adaptations for weathering the winter months.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254379/original/file-20190117-32816-1hh0scn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&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 large ears of a fennec fox would be a liability in a cold climate like where the arctic fox lives.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/yQIxNTQzFJw">Jonatan Pie/Unsplash and Kkonstan/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Wildlife species at northern latitudes tend be larger-bodied with smaller appendages than their close relatives closer to the tropics. Many animals have evolved behaviors to help them beat the cold: herding, denning, burrowing and roosting in cavities are all good defenses. And some animals experience physiological changes as winter approaches, building fat reserves, growing thicker fur, and trapping an insulating layer of air against the skin beneath the fur or feathers.</p>
<p>Nature has devised other neat tricks to help various animals deal with conditions that people, for instance, would be unable to endure.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254393/original/file-20190117-32834-1jj09ed.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&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 animal standing in cold water or on ice benefits from countercurrent heat exchange (1). Warm arterial blood (2) flowing away from the heart warms up the cooler venous blood (3) heading toward the heart.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Counter_current_exchange_in_birds.svg">Ekann</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Have you ever wondered how geese can appear to stand comfortably on ice or squirrels in snow in their bare feet? The secret is the close proximity of the arteries and veins in their extremities that creates a gradient of warming and cooling. As blood from the heart travels to the toes, the warmth from the artery transfers to the vein carrying cold blood from the toes back to the heart. This <a href="https://www.macmillanlearning.com/Catalog/product/principlesoflife-thirdedition-hillis">countercurrent heat exchange</a> allows the core of the body to remain warm while limiting heat loss when the extremities are cold, but not so cold that tissue damage occurs. This efficient system is used by many terrestrial and aquatic birds and mammals, and even explains how oxygen exchange occurs in the gills of fish.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254405/original/file-20190117-32804-j7np1q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Carp in a partially frozen pond are doing fine.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/red-carps-under-ice-pond-near-1088588174">Starkov Roma/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Speaking of fish, how do they not freeze from the inside out in icy waters? Luckily, ice floats because water is most dense as a liquid, allowing fish to swim freely in not-quite-freezing temperatures below the solidified surface. Additionally, <a href="http://dx.doi.org/10.1016/j.conb.2015.01.021">fish may lack the cold-sensing receptor</a> shared by other vertebrates. They do, however, have unique enzymes that allow physiologic functions to continue at colder temperatures. In polar regions, fish even have special “<a href="https://doi.org/10.1142/4917">antifreeze proteins</a>” that bind to ice crystals in their blood to prevent widespread crystallization.</p>
<p>Another secret weapon in mammals and birds during long periods of cold exposure is brown adipose tissue or “<a href="https://www.livescience.com/49652-what-is-brown-fat-facts.html">brown fat</a>,” which is rich in mitochondria. <a href="https://doi.org/10.1172/JCI68993">Even in people</a>, these cellular structures can release energy as heat, generating warmth without the muscle contractions and energy inefficiency involved in <a href="https://www.livescience.com/32475-why-do-we-shiver-when-cold.html">shivering</a>, another way the body tries to heat up. This non-shivering heat production probably explains why people in Anchorage can contentedly wear shorts and t-shirts on a 40 degrees Fahrenheit spring day.</p>
<p>Of course, migration can be an option – though it’s expensive in terms of energetic costs for wildlife, and financially for people who want to head closer to the equator. </p>
<p>As a species, human beings have the <a href="https://doi.org/10.1080/23328940.2015.1135688">ability to acclimate to an extent</a> – <a href="https://www.smithsonianmag.com/science-nature/science-explains-how-iceman-resists-extreme-cold-180969134/">some of us more than others</a> – but we’re not particularly cold-adapted. Maybe that’s why it’s hard to look out the window on a frigid day and not feel bad for a squirrel hunkered down as the winter wind whips through its fur. We may never know if animals dread winter – it’s difficult to gauge their subjective experience. But wildlife do have a variety of strategies that improve their ability to withstand the cold, making sure they live to see another spring.</p><img src="https://counter.theconversation.com/content/108734/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bridget B. Baker does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When you’re warm and cozy inside, it can be natural to wonder if the animals you see outside your window this winter are doing OK. Don’t worry – they’re doing better out there than you would.Bridget B. Baker, Clinical Veterinarian and Deputy Director of the Warrior Aquatic, Translational, and Environmental Research (WATER) Lab, Wayne State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/545192016-03-15T12:30:49Z2016-03-15T12:30:49ZCould humans hibernate?<figure><img src="https://images.theconversation.com/files/115113/original/image-20160315-9282-1px3y40.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">Shutterstock</span></span></figcaption></figure><p>On cold, dark days it is tempting to imagine shutting yourself away until the warmer weather returns. Many animals do just that by entering a state known as torpor, which reduces their bodily functions to a minimum and uses fat stores in their body for energy. Could humans ever hibernate in the same way?</p>
<p>Aside from providing a convenient way to avoid winter, one reason to find out might be the advent of long-distance space travel. A journey to our nearest planet Mars would take <a href="http://www.nasa.gov/offices/marsplanning/faqs/">around eight months</a> using current technology. If we one day hope to visit another star system, even if we could travel at the speed of light, the journey would take years. Being able to go into a state of long-term torpor would make such distances considerably less tedious for the astronauts and conserve vital resources.</p>
<p>As a neuroscientist, I am currently part of a <a href="http://www.esa.int/gsp/ACT/bio/projects/Hibernation.html">team of experts</a> organised by the European Space Agency to work out whether and how we might be able to put humans into a state of stasis. It’s still an open question but, at least in theory, we can’t exclude that it might be possible.</p>
<h2>Body temperature and metabolism</h2>
<p>Torpor appears to have evolved to effectively fill the gaps during those periods of the year when there is no need for certain animals to be out in the world, for example when food is scarce. Technically it refers to a regulated <a href="http://www.ncbi.nlm.nih.gov/pubmed/25123049">state of reduced metabolism</a>, meaning the chemical reactions in an organism’s body that keep it alive slow down. Heart rate, breathing and energy consumption all dramatically decrease and body temperature can also fall.</p>
<p>When and for how long animals enter torpor can vary hugely, from many months of the year, to just a few hours a day over a period of a few months. Some animals, <a href="http://rsbl.royalsocietypublishing.org/content/6/1/132">such as mice</a> and <a href="http://scienceblogs.com/grrlscientist/2006/04/09/hummingbirds-and-torpor/">hummingbirds</a>, enter a state of torpor on a daily basis if they need to save energy. Others, <a href="http://www.independent.co.uk/environment/nature/hedgehog-hibernation-habits-studied-6291152.html">such as hedgehogs</a> and <a href="http://www.bear.org/website/bear-pages/black-bear/hibernation/191-5-stages-of-activity-and-hibernation.html">bears</a>, go into prolonged periods of torpor, usually during the winter (this is what we call hibernation). Those species that go into torpor every year, even if the conditions outside are stable, are called obligatory hibernators.</p>
<p>The fact that large mammals such as bears and even primates, such as the fat-tailed <a href="http://www.nature.com/nature/journal/v429/n6994/full/429825a.html">dwarf lemur of Madagascar</a>, can hibernate means that theoretically humans aren’t too big or energy-hungry to enter torpor. Nor does our evolutionary origin prevent us from doing so, as hibernating animals have been found widely across <a href="http://www.cell.com/current-biology/fulltext/S0960-9822%2813%2900131-0">all types of mammal</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/115114/original/image-20160315-9250-1sxwng1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sleepy time.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Controlled hypothermia and metabolism are already widely used in clinical practice, such as <a href="http://www.ncbi.nlm.nih.gov/pubmed/20609741">during cardiac surgery</a> and to protect tissues from damage when blood flow is reduced, such as after a stroke. Lowering body temperature and metabolism mean cells need less oxygen, enabling their survival in conditions when oxygen cannot be delivered. This process of artificial cooling in humans appears similar to spontaneous torpor in animals in that it includes reduced breathing, heart rate and metabolism. But the key difference is that animals seems to “know” the way to safely and spontaneously enter torpor. Lowering a human’s body temperature by blocking their natural thermoregulation requires the <a href="http://www.scientificamerican.com/article/cool-aid-drug-that-causes/">aggressive use of drugs</a>.</p>
<p>One of the difficulties with replicating torpor is that we don’t really know how animals start and maintain the process. Much research has been devoted to investigating it but few conclusive answers have been obtained so far. On the one hand, it’s possible that torpor is triggered in a “bottom up” fashion, starting with changes occurring in individual cells of the body <a href="http://www.ncbi.nlm.nih.gov/pubmed/23824962">at a molecular level</a>. But a “top down” approach that involves signals from the <a href="http://www.ncbi.nlm.nih.gov/pubmed/17555547">nervous system</a> or <a href="http://www.ncbi.nlm.nih.gov/pubmed/26435475">hormones</a> may also play a role.</p>
<h2>Protecting the brain</h2>
<p>There’s another key issue with the idea of human hibernation, and that’s what it might do to the brain. Animal hibernators regularly come out of torpor for a period of hours or days but often spend that time asleep, before <a href="http://www.cell.com/current-biology/fulltext/S0960-9822%2813%2900131-0">returning to hibernation</a> Similarly, animals emerging from daily torpor also usually <a href="http://www.ncbi.nlm.nih.gov/pubmed/9125697">enter a deep sleep</a>.</p>
<p>This has led some scientists to suggest that, although we tend to think of hibernation as being like a long sleep, torpor actually creates a sleep-deprived state and the animals need to regularly <a href="http://www.ncbi.nlm.nih.gov/pubmed/1945046">compensate for this</a>. We can see this in the way animals’ brainwave patterns are similar when they emerge from torpor to when they <a href="http://www.ncbi.nlm.nih.gov/pubmed/8190354">have been sleep deprived</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/115112/original/image-20160315-9250-oyfm60.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">Spaceship stasis chamber?</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>This maybe because the low metabolism and body temperature of torpor are associated with activity in those brain regions, which are typically associated <a href="http://www.ncbi.nlm.nih.gov/pubmed/17912746">with sleep regulation</a>. But it may also be because torpor changes the brain in a way that could damage it if it wasn’t restored by the mechanisms of sleep. The brain is highly sensitive to a lack of oxygen and so needs to be protected during the time when blood and nutrients supply is reduced.</p>
<p>Another way that torpor affects the brain is by reducing and reorganising the synaptic connections that are the basis of our memories. <a href="http://www.ncbi.nlm.nih.gov/pubmed/20702450">Research in animals such as bats shows</a> that most memories are preserved even after many months in a state of almost complete neuronal depression. But some memories seem to be taken better care of than others, such as the ability to <a href="http://www.ncbi.nlm.nih.gov/pubmed/10715170">remember close kin</a>. So if we wanted to induce human hibernation it would be vitally important to investigate further how memories are retained over a long period of torpor.</p>
<p>While we’re still unsure whether safe prolonged human hibernation is possible, research looking at potential mechanisms may provide the novel insights needed for this to become a reality. Recent technological advances and new pharmacological and genetic tools have already shown great potential to <a href="http://www.ncbi.nlm.nih.gov/pubmed/25129078">induce or manipulate sleep</a>. But to fully understand how we could safely induce human hibernation, we will likely need to dissect key brain circuits and identify the key molecular pathways that regulate our sleep functions.</p><img src="https://counter.theconversation.com/content/54519/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vladyslav Vyazovskiy does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The European Space Agency is exploring what we can learn from animals about long-term deep sleep.Vladyslav Vyazovskiy, Associate Professor of Neuroscience, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/396612015-04-04T08:47:42Z2015-04-04T08:47:42ZLemurs may hold secrets to living longer, but they won’t increase our lifespan<figure><img src="https://images.theconversation.com/files/76964/original/image-20150402-9328-1hlny1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Jonas the lemur defied his small size by living to the age of 29.</span> <span class="attribution"><a class="source" href="http://lemur.duke.edu/nearly-50-years-of-lemur-data-now-available-online/">David Haring, Duke Lemur Center</a></span></figcaption></figure><p>When Jonas the <a href="http://www.eurekalert.org/multimedia/pub/89171.php">fat-tailed dwarf lemur</a> died recently in captivity at the ripe age of 29 years, he was the oldest known of his species. But Jonas not only outlasted members of closely related lemur species held in captivity; he also lived much longer than science would predict based on his small size.</p>
<p>A <a href="http://onlinelibrary.wiley.com/enhanced/doi/10.1111/jzo.12230/">new study</a> in the Journal of Zoology attributed this exceptional longevity to the fact that this lemur species are able to readily enter a low energy state. They can do this for both for long periods of days to months (hibernation), as well as shorter periods of a few hours (known as torpor). Dwarf lemurs live much longer than similar-sized animals. The researchers looked through more than 50 years of records on hundreds of these and three other lemur species at the Duke Lemur Centre. They suggest that increased longevity in hibernators could be the result of cellular machinery that makes them resilient to metabolic stress, which is associated <a href="https://theconversation.com/ageing-isnt-fixed-we-can-manipulate-it-to-live-longer-31808">with ageing</a>.</p>
<p>Among mammals, body size correlates with lifespan: larger species live longer than smaller species. This relationship is not perfect and there are sometimes major exceptions. Jonas and other fat-tailed dwarf lemurs are one of these, meaning they might carry clues to what determines lifespan.</p>
<h2>The flame that burns twice as bright</h2>
<p>In 1908, <a href="https://www.abdn.ac.uk/energetics-research/research/ageing/">Max Rubner</a> proposed the first evidence-based theory of ageing. He noticed that the bigger a species of mammal was, the lower its metabolic rate, meaning that bigger mammals use less energy per kilogramme of body mass than small ones. </p>
<p>But species with bigger body size are also longer-lived. Putting these together, it becomes clear that shorter-lived mammals have a faster metabolic rate. To quote Lao Tzu (and the movie Blade Runner): “The flame that burns twice as bright burns half as long.”</p>
<p>Rubner showed that horses, cows, dogs, cats and guinea pigs each use about 200 kilo-calories for each kilogramme of body weight over the course of their lifetime. So over their lives, each animal, per kilogramme body weight, does the same amount of metabolic work; short-living animals do it faster, longer living do it slower.</p>
<p>This became the <a href="https://archive.org/details/rateofliving031726mbp">Rate of Living Theory</a>. It says that energy metabolism is unavoidably associated with damage which accumulates over time, eventually causing <a href="http://www.nature.com/nature/focus/senescence/">decline in cell function</a> and ultimately death. The faster the metabolism, the more the damage, the shorter the life. In 1956, <a href="http://geronj.oxfordjournals.org/content/11/3/298.long">the Free Radical Theory of Aging</a> proposed that reactive forms of oxygen formed during energy production in cells are what lead to the damage which causes ageing. It’s not proven, but there is much supporting evidence and it’s the best explanation so far. </p>
<p>Evolution shapes the genetics which controls and deals with all this. Natural selection maximises the species productivity in their particular ecologies. In high mortality environments, fast growth and reproduction is required, and ageing is fast. If there is a chance for longer survival, fast growth and reproduction are sacrificed in favour of maintenance of the body, leading to slower ageing and an extended reproductive life. In some species, hibernation has evolved to allow an organism more flexibility in a changeable environment, allowing survival through lean times so that reproduction can re-start when conditions improve.</p>
<p>In hibernating fat-tailed dwarf lemurs, the heart rate drops from 200 to eight beats per minute. Both body temperature and metabolic rate can also drop for up to three months at a time, though they can also enter torpor; a milder state of lower activity. As the Rate of Living Theory predicts, this reduction in metabolic rate is associated with a longer life.</p>
<h2>Could humans achieve a similar state?</h2>
<p>Though some <a href="https://www.youtube.com/watch?v=psAHiYhe1F4">yogic practices</a> do allow substantial slowing of breathing and heart rate, this is for short periods. There is no posture or practice in yoga so far known as “the torpid lemur.”</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/psAHiYhe1F4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Extreme depth free-divers can slow heart rate as an enhanced form of the <a href="http://dujs.dartmouth.edu/winter-2012/the-mammalian-diving-reflex#.VR1vspTF83Q">diving reflex</a>. Some sort of trance-like focus is often used. Holding your breath results in substantial brain cooling by as much as one degree per minute. But this form of control is associated with significant incidences of <a href="http://www.patient.co.uk/health/abnormal-heart-rhythms-arrhythmias">abnormal heart rhythms</a>, and <a href="http://abcnews.go.com/GMA/story?id=125625">deaths among free-divers</a> are not uncommon.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=327&fit=crop&dpr=1 600w, https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=327&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=327&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=411&fit=crop&dpr=1 754w, https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=411&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/77034/original/image-20150403-9332-uyjnmv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=411&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Or holding your breath?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/bookbenbaker/8713406452/in/photolist-6oAaNA-a6yAjP-gPfYBJ-cYbcFL-cKvgzY-cKvZwj-fwFS5k-9YYSDN-dXCjBR-cKviVs-cSqCHy-ejFJSo-c9EdTb-H7HTm-H7Kpc-7XoybN-4njS4C-egYuaJ-egSGEc-egYqYU-egYr2C-6rvRYq-6rrLMt-egYtBq-egYtgU-egYtSf-egYt69-egYorb-bz9ZW7-egSwSn-egSDcF-egYoHA-egYiW9-egSzfB-eh3PzR-egYm1q-egYm6h-egSxvg-egSBov-egYkDJ-egYjQ3-egSz5n-eh3GXe-eh9vRE-aDb6D2-aDeXjL-aDb6AH-aDb6DF-eh3Hgr-eh3FTM">Ben Baker Photography</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Medicine: the real beneficiary</h2>
<p>In 1999, 29-year-old Norwegian Anna Bågenholm <a href="http://www.theguardian.com/science/blog/2013/dec/10/life-death-therapeutic-hypothermia-anna-bagenholm">survived 80 minutes</a> in freezing water following a skiing accident. She was in extreme hypothermia; her core temperature, even after an hour’s journey to hospital, was just 13.7°C. Although there was significant <a href="http://www.patient.co.uk/doctor/cold-injury">cold damage</a> to her body, there was no apparent brain damage at all. This was probably because, when her heart eventually stopped, her brain was so cold its metabolic rate was sufficiently slow it required almost no oxygen. Her heart stopped for at least three and a half hours and her metabolism is thought to have slowed down to just 10% of its normal rate.</p>
<p>The use of <a href="https://www.nice.org.uk/guidance/ipg386">therapeutic hypothermia for treatment of cardiac arrest</a> has become more common in Norway since this case. This can reduce core temperature to 32°C, five degrees lower than usual body temperature. But slowing the heart substantially requires even lower temperatures, and surviving this slowing of the heart would require substantial cooling of the brain and other energy-hungry organs. All which would need a lot of fine tuning to get right.</p>
<p>At this point, at least, I’m not holding my hand up to volunteer.</p><img src="https://counter.theconversation.com/content/39661/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Clancy has received funding from the Australian Research Council, Monash University, AgeUK and Lancaster University.</span></em></p>A new study looking at a long-lived lemur species attributes it to their frequent hibernation-like state. But what lessons can humans learn from this?David Clancy, Lecturer in Biomedical Science, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/363762015-02-02T07:01:19Z2015-02-02T07:01:19ZWhy do groundhogs emerge on February 2 if it’s not to predict the weather?<p>According to legend, if the groundhog sees his shadow on February 2nd, there will be six more weeks of winter; if not, an early spring is predicted. </p>
<p>Of course groundhogs – also known as woodchucks – don’t emerge at this time just to be furry weather predictors. So what’s the real reason? Research into groundhog biology shows they have other priorities in early February than mingling with the people of Punxsutawney, Pennsylvania. </p>
<h2>It’s Groundhog Day!</h2>
<p>Groundhog Day appears to have <a href="http://www.cambridge.org/us/academic/subjects/life-sciences/animal-behaviour/marmot-biology-sociality-individual-fitness-and-population-dynamics">European roots</a>. Early February is midway between the winter solstice and the spring equinox, and throughout history this seasonal crossroads has been celebrated. The ancient Greeks and Romans observed a mid-season festival on February 5th in anticipation of spring. In the Celtic tradition, this period was celebrated as the festival of Imbolog to mark the beginning of spring. Early Christians in Europe embraced this tradition and celebrated Candlemas Day on February 2nd, to commemorate the purification of the Virgin Mary. Customarily on this day, clergy would bless candles and distribute them to the people in the dark of winter in anticipation of spring.</p>
<p>In northern Europe, farmers needed some indication when to start spring planting. They looked for the emergence of hibernators, such as the hedgehog or badger, to signal the coming of spring. Since their emergence occurred in early February, it was believed that if Candlemas Day was sunny, and the hibernator saw its shadow, more wintry weather was ahead. But if it rained or snowed on Candlemas Day, the rest of the winter would be mild.</p>
<p>This tradition was brought to America by the Germans who migrated to eastern Pennsylvania. They found groundhogs in profusion in many parts of the state and decided this mammal was a perfect replacement for the hibernators they’d left behind in Europe. Thus, the tradition continued in America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=463&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=463&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=463&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=581&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=581&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70035/original/image-20150126-24541-1ji5h11.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=581&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Female groundhog emerging from her burrow in late January.</span>
<span class="attribution"><span class="source">Stam Zervanos</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Hibernation helps survival</h2>
<p>In my study area in southeastern Pennsylvania, the average date groundhogs emerge from their burrows is February 4. This fits the folklore and the timing of Groundhog Day. However, predicting the weather is not their objective.</p>
<p>The real reason is related to Darwinian fitness – a measure of an organism’s ability to contribute its genes to the next generation. The process defines natural selection and is based on an organism’s ability to survive and to reproduce successfully. High Darwinian fitness suggests an individual will pass on its genes to many healthy offspring.</p>
<p>Hibernation contributes to Darwinian fitness value. It enhances survival by <a href="http://dx.doi.org/10.1086/367950">saving energy</a> during times of limited food availability. The ability to hibernate is found in several mammalian groups, including all marmots, many species of ground squirrels, chipmunks, hamsters, badgers, lemurs, bats and even some marsupials and echidnas. Curled up in their burrows, they pass the winter months, when food would be hard to come by. </p>
<h2>Hibernation: alternating torpor and arousal</h2>
<p>Hibernation is characterized by a significant drop in body temperature and metabolic function. This process is commonly called torpor. During torpor, body functions including heart rate, breathing rate, and brain activity are reduced. The overall benefit for the animal is saving metabolic energy at a time when it isn’t eating.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70051/original/image-20150126-24531-1dnzd7f.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">This Maine groundhog had 17 torpor bouts where body temperature went up and down.</span>
<span class="attribution"><span class="source">Stam Zervanos</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>However, for some still unexplained reason, hibernators arouse periodically during their hibernating season. These arousals come at a great energy cost. Therefore, arousing must be critical to survival in some way or animals wouldn’t waste the energy on it. Some <a href="http://dx.doi.org/10.1152/physrev.00008.2003">possibilities</a> include maintaining cellular functions or disposing of bodily wastes.</p>
<p>In Pennsylvania, these bouts of torpor and arousal continue throughout the hibernation season, starting on average in mid-November and ending by the beginning of March; a total of about 110 days. In <a href="http://dx.doi.org/10.1093/icb/ict100">one study,</a> an average of 15 bouts of torpor occurred during this period, with arousals in between. Groundhogs aroused for about 41 hours and then returned to torpor for about 128 hours for males and 153 hours for females. </p>
<p>In a 2010 study, we determined that the hibernation periods for groundhogs <a href="http://dx.doi.org/10.1086/648736">increase in length with increasing latitude</a>. The hibernation period matches winter’s duration. The celebration of Groundhog Day would need to change by latitude in order to perfectly match groundhog emergence.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=440&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=440&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=440&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=553&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=553&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70052/original/image-20150126-24546-171mcal.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=553&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Male groundhog (on the right) greeting a female groundhog for the first time after they emerge from their separate burrows.</span>
<span class="attribution"><span class="source">Stam Zervanos</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>It all boils down to sex</h2>
<p>One of the drawbacks of hibernation is the reduced time available for reproduction. Thus, hibernators have developed mating strategies to maximize reproductive success. Groundhog <a href="http://www.jstor.org/stable/1931796">mating strategies</a> involve temporary emergence in early February, mating in early March during during their final arousal, and giving birth in early April. This behavior enhances reproductive success because young are born as early as possible (but not too early) and are able to start feeding in May when lots of food is available. That way they have enough time to gain sufficient weight to survive their first winter hibernation.</p>
<p>But why do groundhogs emerge in February, when mating won’t occur until next month? The answer lies in their <a href="http://www.jstor.org/stable/1383202">social structure</a>. Most of the year, male and female groundhogs are solitary and antagonistic against each other. They aggressively maintain a feeding territory around their burrows and rarely have any contact with each other. February is used to <a href="http://dx.doi.org/10.1093/icb/ict100">reestablish the bonds</a> necessary for mating and ensures that mating can then proceed without delay in early March. </p>
<p>So for the animals themselves, Groundhog Day is more like Valentine’s Day. On February 2nd, groundhogs don’t emerge to predict the weather, but to predict whether their own mating season will be a success!</p><img src="https://counter.theconversation.com/content/36376/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stam Zervanos does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s all about mating success.Stam Zervanos, Emeritus Professor of Biology, Penn StateLicensed as Creative Commons – attribution, no derivatives.