Animals With White Winter Camouflage Could Struggle to Adapt to Climate Change
By Daisy Dunne
Animals that turn white in the winter to hide themselves in snowy landscapes could struggle to adapt to climate change, research suggests.
A new study finds that declining winter snowfall near the Arctic could have varying effects on the survival of eight mammal species that undergo a seasonal color molt from summer brown to winter white each year.
Species most at risk of standing out against the snow include mountain hares, snowshoe hares and short-tailed weasels. Without blending into the background, these animals could find it harder to hunt prey or hide from predators.
However, there are some parts of the northern hemisphere where color-changing mammals could have a better chance of adapting to climate change, the study finds.
These "rescue" hotspots, which include northern Scotland and parts of North America, should be protected by conservationists to give color-changing animals the best chance of adapting to future climate change, the lead author told Carbon Brief.
Visual camouflage is a vital tactic used by both predatory animals, who must hunt while avoiding detection, and their prey, who must hide to avoid being eaten.
But in parts of the northern hemisphere, the changing of the seasons offers a unique challenge to those trying to camouflage with their surroundings.
In winter, when the landscape is snowy and barren, animals with white coloring find it easiest to blend in. However, when spring arrives and snow is replaced with brown soils and growing vegetation, those with mottled brown coloring tend to find it easier to escape detection.
One solution to this problem, used by a range of animals, is to undergo a seasonal moult from brown to white each year.
Scientists have recorded 21 mammal and bird species using this color-changing tactic, including the Siberian hamster, the collared lemming and the willow ptarmigan.
The new study, published in Science, focuses on how climate change could alter the survival chances of eight of these species.
Climate change is causing a decline in winter snow cover in Arctic regions, along with the earlier onset of spring each year. This decline could be causing a "mismatch" between animals with white coats and the snowless ground, explains lead author Prof. Scott Mills, vice president of research for global change and sustainability at the University of Montana. He told Carbon Brief:
"All of these species literally live or die by the effectiveness of their camouflage, which evolution has exquisitely crafted to match the average duration of winter snow."
This mismatch could make some animals, such as hares, more vulnerable to predators, he said. It could also make it harder for predators, such as the arctic fox, to effectively hunt their prey. Mills said:
"One thing to realize is that all 21 of these species, including the carnivores, are prey: Arctic fox get clobbered by golden eagles, weasels are killed by foxes, coyotes, and raptors. For the hares and rodents, tasty snacks for multiple predators, camouflage is everything."
Arctic fox (Alopex lagopus) in snow, Churchill, Manitoba, Canada, North America. Robertharding / Alamy Stock Photo
Charting Color Change
For the study, the researchers first collected coat color and location data for more than 2,500 live animals and museum specimens spanning 60 countries.
They then analyzed this data using modeling to study the molting behavior of animals living in different parts of the world.
The researchers found that, within one species, not all individuals will molt in the winter.
The chances of an animal molting depend on the landscape in which they live. The more snowy the landscape, the higher the chance an animal will turn white in the winter.
This is shown on the chart below, where the number of snow-covered days per year is plotted against the likelihood of turning white in the winter for the Japanese hare (dark blue), the white-tailed jackrabbit (light blue), the least weasel (yellow) and the long-tailed weasel (red).
The probability of a colour-changing mammal having a white winter coat in regions with 0-320 days of snowfall per year. Results are shown for the Japanese hare (dark blue), the white-tailed jackrabbit (light blue), the least weasel (yellow) and the long-tailed weasel (red). Mills et al. (2018)
The chart also includes a "broad polymorphic zone." A "polymorphic zone" is a term used to describe regions where the probability of having either a brown or white winter coat is close to equal.
In these "zones," mammals could have the best chance of adapting to declining snowfall conditions, Mills said. That is because, in these areas, a proportion of each species do not turn white in the winter and are therefore more able to blend in with snowless environments.
These brown-coated animals will be more likely to survive winters with less snow cover and pass on their genes to their offspring. Over time, this would increase the proportion of animals with brown winter coats, allowing the population to adapt—and ultimately survive—in environments with less snow.
The maps below show where the polymorphic zone of two or more species overlap. On the charts, red shows where the zones of two species overlap, while brown shows areas where the zones of three species overlap.
Regions in North America (A) and Eurasia (B) with polymorphic zones in winter coat colour for more than two species (red) and more than three species (brown). Mills et al. (2018)
The charts show that parts of the U.S., Canada and Scotland show the largest overlap.
These regions could be considered "evolutionary rescue zones" where a number of color-changing mammal species could be able to adapt to declining snowfall, said Mills:
"Because areas with the most [coat color] variation evolve most quickly, these 'polymorphic' zones emerge as hotspots for rapid evolutionary response to climate change. Here in the polymorphic zones the populations are most likely to rapidly evolve towards winter brown, and to disperse the winter brown genes out into the adjacent winter white populations."
The species whose range most commonly fall into these zones include the arctic fox, the white-tailed jackrabbit and the long-tailed weasel, the research finds. These species may have the best chance of adapting to declining winter snowfall, Mills said, but it is still too soon to tell what their chances of survival could be:
"To really evaluate risk to various species will require a lot more fieldwork and genetic analyses for other species, like we've been doing with snowshoe hares. We're starting to work with weasels and Arctic fox, but I really hope that this paper initiates researchers around the world to start investigating coat color mismatch."
Picture of Change
The findings should provide "yet another push to policymakers" to reduce the "global carbon footprint," Mills said:
"I hope that the picture of white animals on brown snowless ground 'paints a thousand words' that shows that with continued human-caused climate change and reduction in snow duration, winter white animals on a brown snowless winter background will be in trouble."
The research also shows that conserving "evolutionary rescue zones" could help wildlife to survive future climate change, Mills said:
"I hope it also helps [policymakers] see that other short-term, yet effective, options are available for protecting wildlife in the face of climate change."
The new study provides striking evidence of how climate change could drive the evolution of new characteristics in animals, said Prof. Innes Cuthill, a behavioral ecologist with specialist knowledge of camouflage from the University of Bristol, who was not involved in the study. He told Carbon Brief:
"We have long known that evolution can be rapid, from detailed case studies of particular species in particular locations, but the new research is a great example of how to capture the 'big picture' of evolution of colouration in time and space."
Reposted with permission from our media associate Carbon Brief.
By Gwen Ranniger
Fertility issues are on the rise, and new literature points to ways that your environment may be part of the problem. We've rounded up some changes you can make in your life to promote a healthy reproductive system.
Infertility and Environmental Health: The Facts<ul> <li>Sperm count is declining steeply, significantly, and continuously in Western countries, with no signs of tapering off. Erectile dysfunction is on the rise, and women are facing increasing rates of miscarriage and difficulty conceiving.</li><li>Why? A huge factor is our environmental health. Hormones (particularly testosterone and estrogen) are what make reproductive function possible, and our hormones are increasingly being negatively affected by harmful, endocrine-disrupting chemicals commonplace in the modern world—in our homes, foods, and lifestyles.</li></ul>
What You Can Do About It<p>It should be noted that infertility can be caused by any number of factors, including medical conditions that cannot be solved with a simple change at home.</p><p><em>If you or a loved one are struggling with infertility, our hearts and sympathies are with you. Your pain is validated and we hope you receive answers to your struggles.</em></p><p>Read on to discover our tips to restore or improve reproductive health by removing harmful habits and chemicals from your environment.</p>
Edit Your Health<ul><li>If you smoke, quit! Smoking is toxic, period. If someone in your household smokes, urge them to quit or institute a no-smoking ban in the house. It is just as important to avoid secondhand smoke.</li><li>Maintain a healthy weight. Make sure your caloric intake is right for your body and strive for moderate exercise.</li><li>Eat cleanly! Focus on whole foods and less processed meals and snacks. Studies have found that eating a Mediterranean-style diet is linked to increased fertility.</li><li>Minimize negative/constant stress—or find ways to manage it. Hobbies such as meditation or yoga that encourage practiced breathing are great options to reduce the physical toll of stress.</li></ul>
Edit Your Home<p>We spend a lot of time in our homes—and care that what we bring into them will not harm us. You may not be aware that many commonly found household items are sources of harmful, endocrine-disrupting compounds. Read on to find steps you can take—and replacements you should make—in your home.</p><p><strong>In the Kitchen</strong></p><ul> <li>Buy organic, fresh, unprocessed foods whenever possible. <a href="https://www.ehn.org/clean-grocery-shopping-guide-2648563801.html" target="_blank">Read our grocery shopping guide for more tips about food.</a></li><li>Switch to glass, ceramics, or stainless steel for food storage: plastics often contain endocrine-disrupting chemicals that affect fertility. <a href="https://www.ehn.org/bpa-pollution-2645493129.html" target="_blank" rel="noopener noreferrer">Learn more about the dangers of plastic here.</a></li><li>Ban plastic from the microwave. If you have a plastic splatter cover, use paper towel, parchment paper, or an upside-down plate instead.</li><li>Upgrade your cookware: non-stick may make life easier, but it is made with unsafe chemical compounds that seep into your food. Cast-iron and stainless steel are great alternatives.</li><li>Filter tap water. Glass filter pitchers are an inexpensive solution; if you want to invest you may opt for an under-the-sink filter.</li><li>Check your cleaning products—many mainstream products are full of unsafe chemicals. <a href="https://www.ehn.org/how-to-shop-for-cleaning-products-while-avoiding-toxics-2648130273.html" target="_blank" rel="noopener noreferrer">Check out our guide to safe cleaning products for more info</a>.</li></ul><p><strong>In the Bathroom </strong></p><ul> <li>Check the labels on your bathroom products: <em>fragrance-free, paraben-free, phthalate-free</em> and organic labels are all great signs. You can also scan the ingredients lists for red-flag chemicals such as: triclosan, parabens, and dibutyl phthalate. Use the <a href="https://www.ewg.org/skindeep/" target="_blank">EWG Skin Deep database</a> to vet your personal products.</li><li>Ditch the vinyl shower curtain—that new shower curtain smell is chemical-off gassing. Choose a cotton or linen based curtain instead.</li><li>Banish air fresheners—use natural fresheners (an open window, baking soda, essential oils) instead.</li></ul><p><strong>Everywhere Else</strong></p><ul><li>Remove wall-to-wall carpet. If you've been considering wood or tile, here's your sign: many synthetic carpets can emit harmful chemicals for years. If you want a rug, choose wool or plant materials such as jute or sisal.</li><li>Prevent dust build-up. Dust can absorb chemicals in the air and keep them lingering in your home. Vacuum rugs and wipe furniture, trim, windowsills, fans, TVs, etc. Make sure to have a window open while you're cleaning!</li><li>Leave shoes at the door! When you wear your shoes throughout the house, you're tracking in all kinds of chemicals. If you like wearing shoes inside, consider a dedicated pair of "indoor shoes" or slippers.</li><li>Clean out your closet—use cedar chips or lavender sachets instead of mothballs, and use "green" dry-cleaning services over traditional methods. If that isn't possible, let the clothes air out outside or in your garage for a day before putting them back in your closet.</li><li>Say no to plastic bags!</li><li>We asked 22 endocrinologists what products they use - and steer clear of—in their homes. <a href="https://www.ehn.org/nontoxic-products-2648564261.html" target="_blank">Check out their responses here</a>.</li></ul>
Learn More<ul><li>For more information and action steps, be sure to check out <em>Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race</em> by EHS adjunct scientist Shanna Swan, PhD: <a href="https://www.shannaswan.com/" target="_blank" rel="noopener noreferrer">available for purchase here.</a></li><li><a href="https://www.ehn.org/st/Subscribe_to_Above_The_Fold" target="_blank" rel="noopener noreferrer">Sign up for our Above the Fold Newsletter </a>to stay up to date about impacts on the environment and your health.</li></ul>
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