One way mammals stay warm in the winter is by having a layer of fat under their skin. This fat acts like insulation, helping to keep their bodies warm. Some mammals, like bears, build up a thick layer of fat before winter to help them survive the cold.
Another way that mammals stay warm is by moving around and staying active. When they are active, their bodies generate heat, which helps to keep them warm.
Mammals also have special coatings on their fur or hair that help to keep them warm. For example, some mammals have thick, fluffy fur that traps air and helps to insulate their bodies. Others have a layer of waterproof fur or hair that helps to keep them dry and warm in the snow.
Finally, some mammals have special behaviors that help them stay warm in the winter. For example, some mammals huddle together for warmth or burrow underground to escape the cold.
Don’t forget, wild mammals do freeze to death. Even with the fat and fur and cuddles they can die from extreme cold weather.
They can slow metabolism, gather insulation (like humans and clothing and housing) group together, migrate further south. Etc. But they do freeze and die, edit: every year all the time. Nature is brutal, survival of the fittest.
Deer have thin legs that are pretty much all tendons and bone. So… Their legs do kind of freeze. But because it’s soo thin and their bodies are compact and insulated they can keep the thin amount of blood flowing through the veins thawed out enough.
Also. Once it’s below 20, dry snow becomes a very very good insulator.
Just last night I had to get something from my truck late at night and I just went out in my socks. It wasn’t cold on the feet at all because the snow doesn’t melt.
Felt like walking on styrofoam.
One often overlooked factor is just size. Oftentimes being large enough is adequate to stay warm. Even with a coat of insulation. Gigantothermy and thermal momentum can do a lot for an animal. Now ironically most animals large enough to benefit from this are long since extinct but you still see it in nature.
https://en.m.wikipedia.org/wiki/Gigantothermy
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