15 Incredible Ways Animals Stay Warm When It's Chilly

Winter is coming, and while humans have the option of adding layers of clothing or cranking up the furnace, animals have to rely on their biology or resources to stay warm in the wild. Here are some of the ways our furry and scaly friends survive the cold.

1. LEANING BACK

In addition to having a specialized circulatory system in their feet and flippers, emperor penguins often lean back onto their heels to get their toes off the ice. Their wedge-shaped tails provide stability, and there is no risk of losing heat because blood doesn’t flow through their tail feathers.

2. INCREASING BLOOD GLUCOSE LEVELS

Some reptiles and amphibians like the European common lizard have the ability to increase their glucose levels during the colder months so that lethal ice crystals won’t form and puncture their blood vessels. The process is reversed as temperatures rise.

3. RELAXING IN HOT SPRINGS

Most of the photos on the Internet of Japanese macaques show the pink-faced snow monkeys grooming one another in one of the country’s many natural spas. Known as onsens, the hot springs have become big tourist attractions, which has not deterred the monkeys from returning every winter.

4. MAKING ANTIFREEZE

Scientists have found that Alaskan wood frogs and other species take hibernation one step further: Their bodies freeze during the winter. Glucose in the blood prevents their cells from freezing and prevents dehydration, but all bodily processes (including heart and brain function) stop during this time. According to scientists, the frogs are essentially dead—until spring comes, temperatures rise, and the frogs spring to life again.

5. BUILDING SNOW BUNKERS

Burrowing into compressed snow traps air and creates an insulated pocket, just like how igloos work. Lemmings and other small animals build tunnel systems to stay safe from the wind, cold, and predators.

6. SHUTTING DOWN THEIR LUNGS

Scientists previously thought that freshwater turtles slipped into comas during cold winters, but a 2013 study found that the reptiles still responded to stimuli. Short of going completely comatose, the turtles slow their metabolisms and self-anesthetize, shutting down organs until warmer days return. 

7. GROUP HUDDLE

What’s better than one body covered in layers of warm feathers? Try hundreds of them, standing flipper-to-flipper and moving in unison. Emperor penguins know that huddles are not just for football—they’re also a really good way to share the warmth. The wave of moving tuxedo-clad birds has been compared to a traffic jam, with the slightest movement by one penguin causing a ripple throughout the crowd. Research has also shown that the penguins are not crammed together, but instead stand barely touching so that no penguin’s feathers get compressed.

8. JUST KEEP FLYING

Some birds, like the Alpine swift, head for warmer climates in the winter. A study found that the swifts are able to stay in the air for six months at a time without touching the ground, subsisting on aerial plankton—a mix of small insects, bacteria, and spores found in the air—and forgoing sleep (scientists are divided as to whether the birds skip sleep completely, or catch some shut-eye during short periods spent gliding, rather than flapping). By the time the birds return to their starting location, they have six months to rest and refuel before they start their journey again.

9. BUILDING FAT RESERVES

Some animals eat more in the summer months so that they can store fat for the winter. The fat-tailed dwarf lemur, as the name suggests, uses its tail as a fat bank, increasing its body weight by as much as 40 percent.

10. DEEP SLEEP

Unlike other hibernating animals, North American black bears have the special ability to lower their metabolism without a dramatic drop in body temperature. What’s better than a toasty nap on a cold winter day?

11. STEALING HEAT FROM OTHERS

In a process called kleptothermy, reptiles like the tuatara steal the body heat of animals from completely different species. One study observed that the animals entered the nests of seabirds at night while the owners were still home so that they could benefit from the birds’ higher body temperature. 

12. RELY ON HUMANS

Cats caught out in the cold often seek shelter under cars because the engines are an enticing source of heat (so always check before driving off). Smaller critters also enter homes in the winter to mooch off of the free warmth inside the walls. 

13. GROWING INSULATION

It’s common for animals, from domestic dogs to wild foxes, to grow thicker fur as added insulation. It’s easier to grow than it is to get rid of—creatures like the elk of Colorado have to scratch or lick off their winter coats once the weather warms up.

14. GOING TORPID

Unlike hibernation, which is a long-term state, the torpor state happens in waves and can be frequent. Some species of birds enter torpor every day in the cold months to stay alive by lowering their heart and metabolic rates.

15. SHIVERING

Some animals shiver to stay warm just like we do. And it’s not only the warm-blooded ones—bees also shiver by vibrating their muscles and keeping their wings still.