Polar bears are the largest bears in the world. They are the apex predators of the Arctic, but it takes a lot to survive in such harsh conditions. One key factor is temperature regulation.
Animals can be either cold-blooded or warm-blooded. Just because an animal lives in a cold environment does not mean they’re cold-blooded. In fact, they’re much more likely to be warm-blooded.
Polar bears are not cold-blooded animals. They are mammals, and all mammals are warm-blooded. This is an important aspect of how polar bears survive in Arctic temperatures. They also have additional adaptations that keep them warm on land and in the water. There are only a few cold-blooded land animals that live in the Arctic.
Polar Bears Are Warm-Blooded Mammals
A polar bear, or Ursus maritimus, is the world’s largest bear and land carnivore in general. They live in the Arctic Circle and are part of the Mammalia class of animals.
All mammals are homoiotherms, or warm-blooded. This means they can internally regulate their body temperatures.
Regardless of the temperature outside, a polar bear’s body sends signals to its brain to keep a constant ideal temperature.
How Do Polar Bears Stay Warm?
There are limits to this internal regulation, of course. Like humans, polar bears can’t survive freezing temperatures for long without protection. They need to supplement their internal temperature regulation.
The Arctic is extremely cold, with the average temperature for the whole year being below 50°F (10°C). In Alaska’s Arctic National Park & Preserve, winter temperatures can get as low as -50°F (-46°C).
The large area of the Arctic is part of the tundra biome where it’s dry and cold. This is the most northern limit of where plants, including trees, are able to grow. The Arctic has a growing season that’s only about two months long.
Even the soil is too thin and cold for much to grow. Underneath the first layer of soil is the permafrost, ground that’s always frozen.
Unlike humans, a polar bear’s body already has what it needs to help it stay warm in addition to its homoiothermic traits.
Polar Bears Have Multiple Insulating Layers
Below the skin, polar bears have natural insulation in the form of fatty tissue. This thick layer of extra fat traps heat. It can be over four inches thick (11.4 cm).
This layer of fat is useful for swimming as well. Wet fur doesn’t insulate them well, so their body fat takes the brunt of the work. Polar bear cubs don’t swim in the spring often because they don’t have enough fat yet.
Polar bears have black skin, despite their white appearance. This also helps them stay warm, as the dark color absorbs the sun’s heat.
Polar bear fur is the thickest of all bear species. Close to the body is the undercoat, which consists of very thick, heat-retaining hair. The outer layer is a repellent for ice and water.
The hair doesn’t mat together, meaning they can shake off water and ice with ease.
The outer layer is not hair, but instead, they’re hollow, clear tubes. These tubes trap air for extra insulation. They also give polar bears their white appearance.
The hollow tubes reflect all visible light and the combination of them all makes the fur appear white.
In fact, polar bears can sometimes get too hot and have to cool themselves off in the water.
They Have Special Paws, Ears, And Tails
Polar bear paws have fur on the bottom to protect them from the frozen ground. The fur also creates traction to help them walk.
Additionally, polar bear paws have papillae on the bottom. These are small bumps also create traction and keep the bears from slipping and sliding.
Finally, polar bears have tiny ears and tails in contrast to their enormous bodies. The small size of their ears and tails prevents more heat loss than larger features would.
There Are Cold-Blooded Land Animals In The Arctic
Fish are cold-blooded, and there are 240 species that live in Arctic waters. But much more uncommon are Arctic land animals that are cold-blooded, or poikilotherms.
Cold-blooded animals cannot generate their own body heat. Their body heat is about the same as the temperature of their environment. They have to rely on external regulation to keep a livable temperature.
With such cold Arctic temperatures, it may seem like only warm-blooded creatures could survive there. However, there are six species of animal that range through the Arctic. These include five amphibians and one reptile.
All of these cold-blooded animals have a higher tolerance for cold than most. The common lizard (Zootoca vivipara), for example, can slowly freeze without harm. They then wake themselves up as the temperatures rise.
The Siberian salamander (or newt) concentrates glycerol in their liver. This acts as a “cryoprotectant” which helps them avoid tissue damage from freezing.
In Summary
Being cold-blooded does not relate to the temperature of an animal’s environment. In fact, cold-blooded animals are dependent on their environment to regulate their temperature.
This makes it difficult for cold-blooded animals to live somewhere as cold as the Arctic. There are a few species that do, but they’re rare.
Polar bears, on the other hand, are not cold-blooded, and neither are any other mammal species. They thrive in the arctic, in part because they can internally regulate their body temperature.
They also have physical outer attributes such as a layer of fat and thick fur to keep themselves warm. Even when it’s below freezing, the warm-blooded polar bear has suitable defenses.