The body temperatures of warm-blooded creatures, such as mammals, are constant regardless of the temperature of their environment. Warm-blooded creatures need a lot of energy to keep their body temperature constant. Therefore, the nutritional requirement is of vital importance for warm-blooded creatures. Body temperatures of cold-blooded creatures may vary depending on the ambient temperature. However, this does not mean that they can survive in all conditions. Because the speed of biochemical reactions that sustain life usually decreases as the temperature decreases. In addition, a natural anti-freeze mechanism takes place in these creatures.

Mallard: I have poor circulation, which means my feet are always freezing. I see mallards swimming and waddling around in snow and can't help but wonder how their feet aren't icicles. The answer lies within their unique heat-exchange system, called counter-current circulation. Arteries carrying warm blood from the heart are interwoven with veins carrying cold blood from the feet. The netlike pattern allows blood flowing to the body to be warmed, and blood flowing to the feet to be cooled.

Bison: These gigantic creatures have superb insulation. Bison have "thick skin and underfur, long guard hairs, and layers of fat," according to Yellowstone National Park. Try to look at one and not feel cozy.

Deer: These two deer are oblivious to the fact that it is frigid. Probably because their winter coat keeps them warm, even when it's -30 degrees Fahrenheit outside! Each hair on a deer's winter coat is hollow, trapping air that helps them retain heat. Quilts, window panes and house insulation all utilize air pockets in similar ways.

Grizzly Bear: Grizzly bears hibernate during the winter months, but they don't miss out on all the snow. Grizzlies can be quite active as they forage and prepare for winter. They can sense when it's time to enter their winter den based on the cold temperatures or snow conditions.

Great Gray Owl: Impeccable hearing to locate prey, feathered snow pants to stay warm, and talons to break through ice are just a few characteristics that help great gray owls hunt effectively in the snow. Just watch this great gray owl in action. Snow doesn't seem to be an issue.

Moose: Insulating fur allows moose to survive very cold conditions. Although their long legs can navigate through snow depths of up to 36 inches, they prefer to hang out in the forest where there is greater cover.

Red Fox: One of my favorite videos is of a red fox, diving head first into the snow to capture prey. Impressive. Take a look at some incredible fox photos we've collected from our Facebook community.