Winter-white animals under threat from global warming

Camouflage is a key survival strategy for many animals. But what do you do if your habitat changes dramatically with the seasons? From high mountain habitats to the Arctic north, animals have developed a seasonal wardrobe to stay under cover — and stay alive.

There are 21 species of animals around the world that transform from brown in the summer to snowy white in the winter to blend in with their surroundings — from tiny prey animals like the Siberian lemming to the noble Peary caribou, which takes on a shaggy white coat in winter.

But habitats with extreme seasons are among the most vulnerable to climate change. Winters are arriving later, and snow melting earlier. And animals like this snowshoe hare are being caught out in the wrong look for the season.

A new study published on Thursday in the journal Science found that the showshoe hare, shown here in its summer colors, is already suffering. Population numbers are falling as white winter coats highlight them against snowless ground, making them easy pickings for predators.

Biologist L.Scott Mills and his team have yet to extend their study to other species, but animals like this ptarmigan — a member of the grouse family of gamebirds — could be at risk too. Living in the Eurasian Arctic and subarctic, and high mountain habitats from the Pyrenees to Japan, its habitat is changing fast.

Hunters suffer too. The artic fox changes color to blend in with its habitat and sneak up on prey. But it isn't a top predator. Eagles have a taste for fox meat, and a bright white coat can make them an easy target for the keen-eyed birds.

But there is hope. Animals like the weasel — another critter that makes use of camouflage as both predator and prey — only turns white at high altitudes or in extremely northern territories.

Their cousins in warmer parts of world — like southern Europe — keep their brown coats all year. The difference is down to genetics. And that's why there's hope that evolution could work in their favor.

In areas where the two genetic strains overlap, the scientists hope interbreeding will see the animals adapt to a warmer future. But they warn that "evolutionary rescue" will not be enough to ensure their survival. As always, the real solution is to slow climate change.

"Ultimately, the world must reduce carbon dioxide emissions or else the climate effects will overwhelm the ability of many species to adapt," Eugenia Bragina, one of the scientists behind the study, said.