Photograph by Tom Murphy, Nat Geo Image Collection
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When cold weather arrives, the arctic fox grows into its winter coat—lighter fur that helps it blend into the snow.

Photograph by Tom Murphy, Nat Geo Image Collection

A Frog That Freezes and Thaws, Plus More Ways Animals Cope With Cold

Wild creatures don't have the luxury of curling up under the covers—here's how they make it through winter.

Our winter survival skills often involve staying indoors with plenty of blankets, cocoa, and mindless TV at the ready.

But wild animals don't have that luxury—they have to tough it out in the cold. That made Weird Animal Question of the Week wonder: What are some cool ways animals stay safe and warm in winter? (See some incredible pictures of winter wildlife.)

Winter Coats

Some species pile on the layers, like the arctic musk ox, whose soft undercoat—called qiviut—insulates them from minus 50 degree Fahrenheit temperatures. Polar bears have an extra layer of fat to keep toasty.

Others grow thicker fur in the fall, like white-tailed deer, and some even grow lighter coats to blend into the snow, Sharon Chester, author of The Arctic Guide, Wildlife of the Far North, says via email.

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Musk ox (pictured, a group in Norway's Dovre Sunndalsfjella National Park) have a soft undercoat that keeps out the cold.

North American mammals such as the arctic fox, least weasel, arctic hare, and ermine have this adaptation, Chester says. (Related: "Before and After: See Animals Change Their Coats for Winter.")

The camo works if snow is consistent, Chester says, but it's tougher if snow arrives late and melts early—which is happening more due to global climate change. A 2016 study reported snowshoe hares in Montana that were mismatched to their environment experienced a 7 percent decrease in survival rate.


Wood frogs, which range from the southeastern United States to the Arctic Circle, "hunker down in some leaf litter and freeze solid" into a "frogcicle," says Greg Pauly, curator of herpetology at the Natural History Museum of Los Angeles County.

Frozen Frogs A species of wood frog has a remarkable ability— they're able to survive in frozen water!

When the weather warms again, the amphibians thaw out, no worse for the wear, he says.

That's because wood frogs are freeze-tolerant, which means they can survive ice forming in portions of their bodies, thanks to chemicals such as glucose and urea that protect their cells from damage. (Related: "How Arctic Frogs Survive Being Frozen Alive.")

Other species, including some lizards, turtles, insects, and even at least one mammal can do this.

The arctic ground squirrel, or siksik, can drop its body temperature below freezing while it's hibernating. This is likely due to another process called supercooling, in which the body temperature can go below the freezing point without forming ice.

Another cold-weather toughie is Alaska's red flat bark beetle, which, under lab conditions, can survive cooling down to minus 238 degrees Fahrenheit.

Happy Feet

Flamingos may symbolize the steamy tropics, but three South American species—the Chilean, Andean, and James's flamingo—make their homes in freezing mountain lakes, says Paul Rose, a doctoral student at the U.K.'s University of Exeter.

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James's flamingos feed in Eduardo Avaroa Andean Fauna National Reserve in southwestern Bolivia.

To keep their skinny legs warm, the birds have a countercurrent circulation system, in which “blood returning to the body from the feet is warmed by blood leaving the body to go to the feet, thus reducing overall heat loss," says Chester.

It's a strategy shared by their penguin relatives in Antarctica, he adds.

Do You See What I See?

Reindeer—called caribou in North America—are the ultimate ungulate of winter, of course. Where would Santa be without them?

A 2011 study showed that reindeer can alter their eye color and structure based on the Arctic seasons, where permanent summer sunlight is replaced by 24-hour darkness in winter.

Changes in the reflective membrane behind the eye's retina called the tapetum lucidum ("bright carpet") allows the animals to retrofit their eye to deal with darkness or brightness.

So Rudolph’s nose is pretty awesome, but his eyes are really the prize.

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