Once upon a time, all warm-blooded creatures brought by the struggle for existence in the polar regions faced an important problem – how to combine adaptation to the cold with maintaining limb mobility.
Indeed, if you cover them very tightly with natural heat insulators – subcutaneous fat, wool, feathers and down, they will lose the high mobility necessary for hunting or flight. But there was a way out.
To minimize heat loss through limbs not protected from the cold, polar inhabitants lower the temperature of the blood they contain. For example, the temperature in the paws of polar bears or walruses is normally only four degrees Celsius. The paws of the polar gull itself are literally freezing to the touch, but the bird does not experience any discomfort from this.
The fact is that his legs are heat exchangers, in which the arteries and veins are located very close to each other. Thus, the cold venous blood that has given up the oxygen, passing from the paws to the heart, is heated by the arteries, through which the blood flows in the opposite direction, heated by the body wrapped in natural thermal insulation. It is this mechanism that saves the polar hearts from temperature drops. Such a natural radiator helps polar animals not only to retain heat, but also to discharge its excess that occurs during physical exertion.