In the North Pole, temperatures can hover around 0 °C and can drop well below that in the winter (up to -50 °C or -60 °C), yet the polar bear can maintain its temperature at around 37 °C.
In order to survive in such climates, polar bears have several features that allow them to live comfortably in the harsh environment.
In order to survive in such climates, polar bears have several features that allow them to live comfortably in the harsh environment.
FUR and SKIN
The most noticeable part of the polar bear is their white, sparkly fur, and it's this fur that provides a lot of thermal protection for the animal.
Their fur coats have two layers: an outer layer made up of coarse 'guard hairs' and under that a shorter, more dense layer of 'underfur' right on top of the skin.
The transparent guard hairs are useful for maintaining a core body temperature by absorbing infrared radiation, which is a form of heat. In many other animals, when heat is naturally emitted from the body it will dissipate into the environment - however in polar bears, the guard hairs allow them to re-absorb that heat so that it won't be lost to their surroundings (asknature.org).
The smaller, more dense hairs that make up the underfur mainly help retain body heat.
The transparent guard hairs are useful for maintaining a core body temperature by absorbing infrared radiation, which is a form of heat. In many other animals, when heat is naturally emitted from the body it will dissipate into the environment - however in polar bears, the guard hairs allow them to re-absorb that heat so that it won't be lost to their surroundings (asknature.org).
The smaller, more dense hairs that make up the underfur mainly help retain body heat.
The skin of polar bears also plays a role in thermoregulation. Although we all think of polar bears as white due to the color (or lack thereof) of their fur, polar bears actually have black skin! The color of this skin, as seen in the image below, helps increase the amount of solar heat absorption.
FAT
Additionally, polar bears have a very thick layer of adipose tissue underneath the skin that minimizes heat loss and increases heat retention in the body. We already covered how polar bears love to eat lipid-rich seals, and this is partly why - in their blubber, seals have a LOT of brown adipose tissue which has a low thermal conductivity and is responsible for heat production. The bears can obtain this tissue for themselves through seal-heavy diets, and essentially the more fat that a polar bear can consume, the more protection it will have come wintertime (Cannon and Nedergaard, 2004).
Additionally, polar bears have a very thick layer of adipose tissue underneath the skin that minimizes heat loss and increases heat retention in the body. We already covered how polar bears love to eat lipid-rich seals, and this is partly why - in their blubber, seals have a LOT of brown adipose tissue which has a low thermal conductivity and is responsible for heat production. The bears can obtain this tissue for themselves through seal-heavy diets, and essentially the more fat that a polar bear can consume, the more protection it will have come wintertime (Cannon and Nedergaard, 2004).