Top 10 Ways Animals Stay Warm in Cold Weather

During the frigid winter months, we humans take shelter inside our cosy homes – and if we do venture outside, it’s beneath several layers of extra clothing. But what about wild animals? How do they cope without hot water bottles and a thermostat? Some adopt the same methods as us, and have thick furry coats or hunker down in snuggly dens or nests. Others decide to avoid the cold altogether by migrating. Those that stay put and brave the weather have evolved all sorts of ingenious adaptations for staying warm. Below are our top 10 ways that animals manage to stay warm and outsmart the freezing winter.

1. Huddle Together

Huddling together is very common in the animal kingdom as a way of keeping warm. But the biggest huddler of them all is the emperor penguin. As many as 5,000 individuals may crowd together at once to ensure their collective survival. Huddling is known as social thermoregulation and allows the penguins to share body heat when Antarctic conditions are extremely cold and windy. At the centre of the huddle, the penguins’ core temperature can reach 37°C, even if the air outside the huddle is -30°C. The penguins take it in turns to occupy the warm centre of the group, spending an average of 50 minutes in the huddle. Some penguins have even been observed eating snow after they leave, possibly to lower their body temperature. Huddling is so efficient that emperor penguins save half the energy they would otherwise expend by not gathering together.

2. Grow a Winter Coat

Some animals, such as mountain hares, stoats and arctic foxes, adopt a very simple solution to surviving the cold winter months: grow a warm winter coat. Rather than simply sprouting more fur, mammals grow two types: a thick, insulating downy undercoat, and a coarser overcoat made of guard hairs. These coarser hairs repel snow, conserve warmth and absorb heat from the sun. Arctic foxes go one step further and even grow hair on their feet which acts as snow shoes when navigating their winter terrain.

A change of coat also comes with a change of colour. Scientists think that white winter coats trap more air, because the lack of pigment creates more space in the hair shafts (which, in turn, makes them more insulating). A white winter coat is also an excellent way for animals to camouflage themselves in a winter environment.

3. Fluff Up Feathers

How do birds, survive freezing temperatures? Just like people, they shiver to stay warm. This causes their metabolic rate to go up, which generates body heat. Shivering is only a short-term solution, though, as it requires burning a lot of calories. A steady supply of food is essential (which is why feeding garden birds during the winter can be lifesaving).

But generating heat is only the first step. The bird also has to maintain its higher temperature. Thankfully, by fluffing up its feathers, it can trap pockets of air, providing a nice insulating air blanket. There’s another advantage, too. In cold weather, birds can often be seen tucking their heads and bills into the warmer layer of air under their back feathers. Breathing in this warmer air maintains their body temperature more efficiently.

One way birds lose heat is through their thin, featherless legs. Balancing on one leg means that the other can be tucked up warm and away from the cold ground. Penguins, which have to stand for long periods on ice, rock back on to their heels to keep their more vulnerable toes off the freezing ground. Another way birds avoid getting cold feet is a counter current heat exchange system in their legs. The blood vessels going to and from the feet are very close together, so blood flowing back to the body is warmed by blood flowing to the feet, reducing heat loss.

4. Take a Hot Bath

Japanese macaques are the most northern-living of all the primates in the word (excluding humans). Japan also happens to be the snowiest country in the world, so the macaques need a range of adaptations to keep cosy during the long winters. Not only do they have very thick downy coats and huddle together to keep warm, they have another trick up their sleeves: taking a thermal bath. These monkeys seek out mountainous hot springs in the Jigokudani region of Hokkaido. The steamy water keeps the macaques warm, while also reducing cold-induced stress. This is why they appear so relaxed and calm. Scientists have even linked the reduction in stress hormones to greater reproductive success. It turns out that the highest ranking females are the ones who take longer baths!

5. Antifreeze in the Blood

Cold-blooded creatures like most fish, amphibians and invertebrates cannot rely on body heat to survive freezing winter conditions. Some have adopted an ingenious alternative strategy instead: carrying antifreeze in their blood. The antifreeze proteins bind to ice crystals, preventing them from growing large enough to cause tissue damage. Take the notothen fish, for example, which uses this adaptation to survive among Antarctic glaciers, where temperatures can drop as low as −2.6°C (the coldest temperature ever recorded for liquid seawater).

The wood frog takes this adaptation to even greater extremes. When temperatures drop, water flows out of the frog’s body and eventually freezes as a protective layer of ice. Meanwhile, glucose and urea build up in the body and act as antifreeze for vital cells and organs. Around 65% of the water in the frog’s body freezes and it spends the winter frozen solid. During this time, it doesn’t breathe and its heart stops beating. To all appearances, the ice-bound amphibian is dead. Yet amazingly, when spring comes around, the frog thaws back to life, ready for mating!

6. Fat Reserves

The benefits of building up fat reserves are two-fold. Firstly, a layer of fat acts as insulation. Seals and whales have a thick layer of adipose tissues below the skin that covers the entire body, except for the fins or flippers. This is known as blubber and can reach 23cm thick in bowhead whales! In colder water, blood vessels in the blubber constrict (get smaller). This reduces the energy required to pump blood around the body, thereby conserving heat.

Fat reserves are doubly beneficial because they can also be burned to provide energy and heat to the body. Many animals bulk up in preparation for winter temperatures and food scarcities. For example, the fat tailed dwarf lemur stores fat in its tail (which is as long as its body and up to 40% of its total body weight). Bulking is an especially useful tool for migrating birds as they prepare to undertake strenuous journeys south to avoid cold winter temperatures. Other creatures, such as bears and marmots, build fat reserves in order to hibernate through the winter. This enables them to stay toasty-warm in their underground dens for months at a time, without ever having to venture out into the cold for food.

7. Hibernation

Perhaps the best way to brave the cold is not to. Many small mammals, reptiles, amphibians and insects choose to sleep for weeks or even months during the winter. When hibernating, an animal’s metabolism, breathing and heart rate slows down, enabling it to sleep for long periods without burning much energy. A hedgehog’s metabolic rate drops to 2 per cent of its normal summer activity, while its heart rate falls from 110-150 beats per minute down to 5-70 and it can go 2 hours without a single breath!

It is not as straight forward as just falling asleep, though. Preparation is key. Hibernating bears will eat 20,000 calories per day before hibernating – 4 times their usual intake! They can weigh up to 450–550kg by the time they are ready to sleep. This allows them to slowly burn through their fat reserves until spring arrives.

8. Make a Shelter

Many animals adopt the same strategy as people when its cold: hide away in a nice cosy house (or – in their case – a burrow, nest or tree hollow). These homes offer protection from extreme temperatures, as well as predators.

Surprisingly, snow itself can act as a good shelter. The light and fluffy variety is mostly trapped air, which makes it a good insulator. The Willow Ptarmigan, a small arctic grouse, exploits this property by spending long winter nights in cosy snow caves – temporary burrows it excavates in loose snow.

9. Curl Up Tight

Have you ever noticed how your pet cat or dog will spread out in the sun and curl up when it is cold? Well, wild animals do the same! In chilly weather, they tuck themselves into a heat-conserving ball. This is because heat is lost through the skin. Because snuggling up into a round shape lowers the surface area of exposed skin, the animal can reduce heat loss. Some animals – such as foxes and squirrels – even employ their bushy tails like a blanket, wrapping them around their faces for extra warmth.

American pikas can also moderate body temperature through posture (to some degree). These little mammals live in cold, mountainous regions and are vulnerable to heat loss due to their small size. During cold spells, they will squeeze into a fluffy ball. This spherical posture reduces their surface area to volume ratio, helping them hold in precious body heat. Plus, they have small ears, appendages and no tail, helping to lower their surface area even further.

10. Migrate Away

Why bother fighting freezing conditions when you could go somewhere warm? Many birds take flight at the first hint of winter weather, and migrate to warmer altitudes or latitudes. But while the idea of spending winter in balmier environments may paint an idyllic picture, the journey is not so simple for most. In their efforts to avoid the cold, many birds complete record-breaking voyages. The bar-headed goose has one of the highest migrations, travelling over the Himalayas at altitudes of up to 7,000m, where oxygen levels are 90% lower than at sea level! The great snipe completes the fastest long-distance migration, travelling over 6,800km at speeds of up to 60mph. Finally, the Bar-tailed Godwit holds the record for the largest non-stop flight, enduring over 6,835 miles without food or sleep. Perhaps it would have been easier to stay at home and brave the winter..!

For some species, finding a more comfortable climate does not necessarily involve long, arduous journeys. The blue grouse, for example, has the shortest migration in the world, descending just 300m from mountainous pine forests to deciduous woodlands in Canada and the United States. Having a warmer home just a short stroll away sounds just the ticket!

Take a look at our How Animals Keep Warm in Winter gallery for more images of animals beating the cold.