How Is A Caribou Adapted To Life In Freezing Snow And Ice?

The caribou is a north American deer that lives in temperatures that fall well below freezing – sometimes 20-30 degrees Celsius below and rarely down to about minus 50!. They have thick woolly fur coats, and plenty of fat under the skin to insulate their body but their greatest adaptation is the way they keep their feet from freezing.

They spend much of their time with their feet in deep snow but they don't ever get frostbite. They manage this because they have a sort of heat exchange system in their legs. Their veins, the blood vessels that take the blood from their feet back to the heart, run directly alongside the arteries that carry fresh blood from the heart to their feet. This arterial blood is warm because it has come from deep inside the caribou's body and heat is exchanged from the arteries to the veins, keeping the blood in the veins from freezing.