How can geese or ducks stand or sit for hours on an ice shelf next to a river’s open water? Of course they carry a nice, plump down coat, but what about their exposed feet?
First, their legs and feet have very little soft tissue. Even the muscles that operate the foot are mostly higher up in the leg and connected to the bones of the feet with long tendons.
Lack of soft tissue means less need for warm blood.
Second, warm blood flowing through the birds’ arteries passes close to cold venous blood returning from the feet.
As arterial blood warms up the venous blood the feet are kept cool, and the few tissues in the feet are supplied with just enough warmth to avoid frostbite.
Mammals, like elk, have thick fur coats. An elk’s winter coat has two layers: a dense, woolly undercoat covered with thick, long guard hairs.
Each guard hair contains thousands of tiny air pockets making it waterproof and providing insulation. In very cold weather, snow on the thick coat often doesn’t melt because the animal’s body heat is held in by the undercoat. Also, elk can make their hair stand on end, creating a thicker coat that traps more air.
As a final trick, when deep snow and bitter cold become major problems for elk, they will either gather in tight groups on windswept areas to take advantage of warmth and safety in numbers, or move into the pine trees, seeking insulation.
Whatever it takes, the animals that spend their winters here have evolved some amazing strategies to survive.
— Bruce Auchly, Fish, Wildlife and Parks