Posted by Janet Harriett on Jan.27, 2010

Thermograph of a polar bear, courtesy of arno / coen

Polar bears are built for the cold. As the photo to the left shows, polar bears lose almost no body heat except through their eye area, nose, tail and paw pads. Polar bears’ Arctic-weather adaptations are so good at keeping body heat in and taking advantage of what heat there is in the Arctic that polar bears run a much higher risk of overheating than chilling. While you may not need to battle 30-below temperatures, you can take some lessons from polar bears in keeping your family warm and safe when they venture outside in the cold weather.

Layer

A polar bear’ s fur coat actually consists of two layers. The whitish fur overlayer that we see covers a dense coat of underfur. The layers together help insulate the bear, the same way that a thick winter jacket over a sweater keeps a person warm.

The fur appears white because each individual strand is hollow. The hairs themselves are transparent, but refract light to appear white to creamy yellow, depending on how clean the bear is. Hollow hairs trap air within the hair shaft, as well as between strands and layers. This is the same basic principle you can use to bundle up your house with removable storm windows or multi-pane window glass.

Waterproof

Besides being built in insulating layers, polar bear fur is covered with a layer of natural oil to repel water. Water near the skin in cold weather sucks body heat right out of any mammal, polar bear or human. In winter gear, a water-repellent outer layer keeps dry, which is the first stage of keeping warm.

Reduce Surface Area

Polar bears are build with stocky legs and a small tail and ears. Smaller extremities mean less surface area to radiate body heat. By reducing the surface area exposed to air, polar bears reduce heat loss. Humans can’t instantly shrink our ears, noses and fingers, but we can keep them covered and minimize the external surface area of our bundled-up selves and families. Earmuffs press ears against the side of your head, effectively eliminating a lot of radiant surface area on the backs of ears. Mittens reduce the exposed surface area of hands which keeps hands warmer than individually-fingered gloves, though the warmth comes at the expense of dexterity. A neck wrap that keeps nose and lips protected against the weather is always a good choice.

Traction Control

Polar bears have fur on their feet. This natural “tread” and the rough surface of the paw pads helps them keep their footing on the pack ice. The claws help with traction, too. With human winter footwear, tread is the key to reduce slippage. A smoother-soled sneaker or fashion boot may work well on dry land or liquid water, but on ice and snow, you want tread to keep your footing. Fur also helps reduce heat loss through paws to an extent.

Insulate

Polar bears are insulated with a blubber layer four inches thick. While this is not a healthy physiological state for a human being, body fat does play an important role in health, as well as helping retain heat and regulate internal temperatures. There is no universally accepted guideline for what constitutes a healthy percentage of body fat, but most guidelines put the lower limit for women around 15% and the upper limit around 35%. Unlike polar bears that have to rely on their fat for insulation, human beings can take advantage of insulating clothing technology like thermal-weave undergarments, which also have the advantage of being much less bulky than nature’s insulation.

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Posted under Living, Nature and Environment.