Struggling to stay warm this winter? Some mammals are much better at maintaining body heat than we are.

Polar bears use their hair to keep warm and to camouflage. Although their outer layer of hair looks white, it’s actually transparent, and their skin is black. Each hair is hollow and covered in tiny bumps. This means that the light travels inside the hair, gets trapped, bounces around and scatters off the bumps, causing it to emit white light, and making polar bears appear white. This scattering also helps keep the polar bears warm – as the thermal radiation from the bears body is released, the hairs scatter and reflect it back down, trapping the heat and keeping the bears warm.

Some endothermic (warm-blooded) marine mammals like whales and seals use blubber to stay warm. Blubber is a thick layer of fat that has low thermal conductivity, which means it doesn’t transfer heat very well. So once the whales and seals are warm, the heat is not lost to the colder outside temperatures as easily as it would be through tissue like muscle. You can experiment at home with heat transfer through fat with this experiment.

Some animals like echidnas avoid winter altogether by hibernating. During colder periods when they lose body heat and their food source is limited they conserve energy by slowing their metabolic rate, lowering their body temperature, and slowing their breathing and heart-rate. An echidna’s body temperature is usually around 31 degrees Celsius, but during hibernation their temperature drops to the soil temperature.

Since we can’t hibernate this winter, why not try getting warm and cosy with layers and hot drinks. And if you do stay indoors to hide away from winter, you can always check out our science courses!