Why Do Animals Have Fur?

Step 1 of 5

Still air is the insulator.

Air hardly carries heat at all, as long as it stays put. Fur's whole job is to hold a layer of air against the skin and stop the wind from stealing it away.

Step 2 of 5

Fluffing it up makes it warmer.

Tiny muscles at the base of each hair can stand it upright. A standing coat is thicker, so it holds more air — which is why a cold animal looks twice its size.

Step 3 of 5

Goosebumps are the same muscles.

You have those little muscles too. When you are cold or startled they pull, but with almost no hair left to stand up, all you get is the bumps.

Step 4 of 5

Most animals have two coats.

Underneath is a soft, dense layer that does the warmth. On top are longer, coarser hairs that shed rain and take the wear — so the working layer stays dry.

Step 5 of 5

It changes with the seasons.

As the days shorten, many animals grow a thick winter coat and drop it again in spring. Some, like the arctic hare, change colour at the same time and go white for the snow.

Fur, feathers and a penguin's coat are all solving the same problem the same way — and so is your jumper.