It's a fashion fact that the colder your environment the more winter accessories you need.
Even some animals have two coats: one for summer to match the bare ground and a winter white to match the snow.
But what if there is no snow and you can’t take off your coat?
In a new study in Science, scientists examined 21 species in 60 countries that shed brown coats and turn white to match the snow. As global climate change leads to less snowfall, many of these animals are turning white when there is no snow—making them more vulnerable.
But the study found some possible refuges for these creatures: Geographic regions that are home to colour-changing species with both winter colour types (picture a forest full of snowshoe hares, some brown, some white).
By protecting such areas, humans could give the species to spread their darker-coat genes and outsmart climate change.
Some species sporting seasonal camouflage are the snowshoe hare, Arctic fox, and ptarmigan.
Their colour-changing ability is "a trait that evolution has shaped to carry these animals through climate change over deep time," says study leader L. Scott Mills, a wildlife biologist at the University of Montana.
Snowshoe hares, for instance, once ranged as far south as North Carolina, but now only extend to West Virginia due to lessening snow—a pattern researchers have found in other colour-changing species, says co-author Jennifer Feltner, a Ph.D candidate at the University of Montana.
The amount of sunlight in a day triggers the hares to change their coat, regardless of whether there is snow or not. Conspicuous without their white camo, these hares are easily killed off by predators.
"Mismatch kills," Mills says—and hares have a lot of predators. Indeed, Feltner says her lab mates have dubbed them “the cheeseburgers of the forest,” because they’re on everyone’s menu, from owls to mountain lions.
A snowshoe hare leaps through the snowy landscape in its winter coat.
PHOTOGRAPH BY ROBBIE GEORGE, NATIONAL GEOGRAPHIC CREATIVE
The hares also don't know they don’t blend in and don’t alter their behaviour even after losing their camouflage, Mills says, likely a trait of most of these colour-morphing species.
Ptarmigans are another story. Because the birds rely on colour to attract mates, Mills says, male ptarmigans that turn white will stay that way, snow or not, until they mate.
After that “they find a mud hole or even feces and roll around and turn themselves brown,” regaining their camouflage after using their conspicuous colour to attract females, Mills says.
Mills proposes that, because climate change is happening so quickly, "the same selective forces that led to winter brown and white morphs could be a tool for conservation."
For instance, the hot spots the team identified—including many parts of northern North America and Eurasia, such as the Pacific Northwest—are prime candidates for protection, and thus a chance for colour-changing species a chance to recover.
Rock ptarmigans sport their winter plumage in Sweden's Sarek National Park.
PHOTOGRAPH BY ERLEND HAARBERG, NATIONAL GEOGRAPHIC CREATIVE
"Evolution happens fastest when populations are large and when they are connected," Mills says.
Keeping populations of winter-white and winter-brown animals connected would allow them "to disperse the more protective, darker coat genes to the nearby winter white populations to aid their adaptation as snow cover becomes less frequent."
Fostering large population sizes and natural connectivity across these landscapes “should be our first and biggest effort," Mills adds.
Lead Image: An Arctic fox stalks the coast of Churchill, Manitoba. PHOTOGRAPH BY MATTHIAS BREITER, NATIONAL GEOGRAPHIC CREATIVE