Cold Feet of Penguins

Additional Information about Penguins..

Why do Antartic penguins' feet not freeze in winter when they are in constant contact with the ice & snow? After doing research for so long, this is what i got.!

Penguins, like other birds that live in a cold climate, have adaptation to avoid losing too much heat and to preserve essential body temperature of about 40 C. The feet pose particular problems since they cannot be covered with insulation in the form of feather or blubber, yet have a big surface in area (similar consideration apply to cold climate mammals such as polar bears).

Two mechanisms are at work. First, the penguin can control the rate of blood flow to the feet by varying the diameter of arterial vessels supply in the blood. In cold condition the flow is reduced, when it is warm the flow increases. Human can do this too, which is why our hands and feet become white when we are cold n pink when we are warm. Control is very sophisticated and involves the hypothalamus and various nervous and hormonal system.

However, penguins also have "counter current" heat exchangers at the top of the legs. Arteries supplying warm blood to the feet break up into many small vessels that are closely allied to similar numbers of venous vessels bringing cold blood back from the feet. Heat flows from the warm blood to the cold blood, so little of it is carried down the feet.

In the winter, penguin feet are held a degree or two above freezing-to minimize heat loss, whilst avoiding frostbite, ducks and geese have similar arrangement in their feet, but if they are held indoors for weeks in warm condition, and then released onto snow and ice, their feet may freeze to the ground, because their physiology has adapted to the warmth and this causes the blood flow to feet to be virtually cut-off ans their foot temperature below freezing.