Six fascinating ways animals survive the cold

In some of the coldest places on Earth, very little can survive.

Anything that does live in these harsh environments often has to endure not only temperatures well below freezing but also minimal food and sunlight. We explore how some of the world’s hardiest animals have evolved ways to cope with these extreme conditions.

1. Winter coats

Most of us are used to putting on layers when the weather gets chilly. Many animals rely on having thick coats that provide insulation by trapping warm air close to their bodies.

For instance, the musk ox’s long, shaggy hair has enabled the species to survive in the Arctic for thousands of years. The thick fibres of their outer coat are known as guard hairs and protect the undercoat from snow and rain. The undercoat is made of shorter, finer and softer hair, which provides excellent insulation against temperatures that often drop below -40°C.

Some animals, such as bison, mountain goats and deer, have thinner coats during the warmer months to prevent overheating but grow thicker coats for winter. Bison even develop a layer of fat for added insulation.

A recent study found that polar bear fur contains grease that prevents it from freezing after they dive into the water to hunt. Scientists believe this grease could potentially be used to develop anti-ice surface coatings.

But coats aren’t just about keeping warm. Sometimes they also double up as camouflage. For example, the snowshoe hare sheds its brown summer fur and turns white in the winter to blend in with its snowy surroundings, making it less likely to be seen by predators.

2. Huddle together

When it comes to withstanding the cold, emperor penguins are among the world’s hardiest birds. They’re uniquely adapted to live in environments where little else can survive.

They’re the only species of penguin that breeds during the Antarctic winter. This means they must endure temperatures as low as -50°C and extreme wind speeds of up to 200 kilometres per hour. Despite these harsh conditions, they still manage to keep their eggs warm.

These hardy penguins have many features that help them do this, including a double layer of feathers as well as small bills and flippers to prevent heat loss.

But the emperor penguin’s true strength comes in numbers. While other species of penguin are generally territorial during the breeding season, emperor penguins work cooperatively by huddling together for warmth.

These huddles can be made up of hundreds, sometimes even thousands, of individuals. Those on the outside are exposed to the full force of the weather, so the colony slowly rotates, allowing each individual to spend time in the warm centre, which can be more than 20°C.

3. Heat exchange

Animals that live in cold environments need to reduce heat loss as much as possible.

A larger surface area usually means more heat loss. This is why having smaller extremities, such as ears, limbs or other appendages, can help animals retain heat.

The priority for most creatures is to keep their internal organs at a stable temperature. This often means sacrificing heat from their extremities to maintain their core temperature. This is why in winter your hands start to go cold first.

To stop their extremities from getting too cold, some animals have a heat exchange system. In these systems arteries and veins are close together and transfer heat to each other.

As warm blood from the core pumps through the arteries to the extremities, heat transfers to the cooler blood being carried from the extremities back to the core by the veins.

This system, coupled with the ability to adjust how fast their blood flows, helps prevent a penguin’s feet from freezing when they’re constantly standing on ice. It also helps the animal to maintain a stable internal body temperature. The blood cools as it flows through the feet, but it’s then warmed as it returns to the centre of the body.

This counter-current circulation system is seen in the legs of all birds as well as some marine mammals, such as whales, which use it in their flippers and tails.

4. Nasal radiators

Some animals, such as the saiga antelope, have to cope with both cold and warm weather.

This antelope is an ice age survivor that once lived alongside woolly mammoths on the northern grasslands. It’s often dubbed the world’s weirdest antelope due to its large, bulbous nose.

Saigas historically lived from Hungary to northeast China, grazing across the vast Eurasian steppe, but today these unusual antelopes are confined mainly to Kazakhstan.

This environment is prone to extreme seasonal temperature swings, so the antelopes have to be well adapted to freezing cold winters and hot, dry summers. This is where their most prominent feature comes in.

The saiga’s nose contains large chambers that help to filter out dust and cool the air when it’s hot. When it’s cold these chambers warm the air up before it reaches the lungs.

Other animals that have specially adapted noses include the bearded seal that lives in and around the Arctic Ocean. Scientists found that the noses of these hardy marine mammals have a built-in heating system.

When these seals breathe, air enters their nostrils and goes into a labyrinth of nose bones called maxilloturbinates. These bones are porous and lined with mucus-rich tissues that trap heat. Compared with their subtropical relatives – the Mediterranean monk seal – the noses of bearded seals retain significantly more heat and moisture.

5. Freeze!

For most animals, freezing solid would be fatal, but some, such as the wood frog, have adapted to survive in this state.

Wood frogs live in Alaska, Canada and the northeastern USA. Conditions here can be harsh during the winter months with temperatures recorded as low as -60°C in Alaska.

As the temperature drops, these hardy amphibians nestle down in leaf litter on the forest floor to protect themselves from the elements. As the chilly weather draws in, the body of the frog freezes. Low temperatures cause ice crystals to form within its blood vessels and internal organs.

To protect against this, the frog’s liver releases large amounts of glucose, which is like sugary syrup. This acts as an antifreeze, preventing the cells from completely freezing and becoming damaged or punctured by large ice crystals. The frog can remain frozen for up to eight months, gradually thawing as temperatures warm during spring.

Other animals that can survive being frozen include tardigrades, the woolly bear caterpillar and icefish. The icefish has antifreeze compounds constantly circulating in its blood as it swims about in the supercold water.

6. Hibernation and dormancy

During the cold season, many of us are tempted to stay wrapped up cosy in bed and would if we could. Many animals hibernate as a survival strategy for getting through the winter.

Animals that lack the adaptations to remain active during the winter will either migrate to warmer climates or hibernate or become dormant.

Hibernation or dormancy is where animals become inactive to survive the harsh winter conditions when food is often scarce. They enter a dormant state that lowers their metabolism to conserve energy. Their heart rate and breathing slow down and their body temperature can drop to just a few degrees above the ambient temperature.

Some animals don’t eat during their hibernation, so in the months beforehand they eat lots of food to build up their energy stores to get them through the winter.

Hibernation works differently for different species. For example, the wood frog freezes solid when it enters a state of hibernation, but many animals avoid the ice by seeking shelter in underground dens or burrows.

Hibernation is more common among smaller animals, such as dormice, hedgehogs, bats, butterflies and moths.

Larger animals, such as the American black bear, enter a lighter sleep called torpor. This is not true hibernation, but a type of dormancy.

During this state their body temperature usually drops by just a few degrees, remaining warmer than true hibernating animals. This means bears are able to wake up from their sleep much faster than animals that enter deep hibernation. To maintain this temperature, however, they need huge stores of energy.

This is why in the lead up to torpor, bears will spend most of their time eating to gain weight. Bears in northern Alaska can remain in their dens for up to seven months of the year, surviving off their fat reserves alone. During this time, they don’t eat, drink, urinate or defecate, and they lose about a third of their body weight.