Traveling to Churchill evokes images of pristine white polar bears. This “white” fur blends in with snow and ice to camouflage the animal, not from predators, though more so from prey, such as seals. The black also acts as a receptor for heat absorption from sunlight.
Polar bear with blackish tongue. Natural Habitat Adventures photo.
Each polar bear hair is hollow in core, pigment-free and transparent that scatters and reflects sun-light. The same principle happens with ice and snow.
Just after the molting season in spring and early summer, polar bears appear most white since they are cleanest then. During the seal hunting season out on the Hudson Bay, polar bears absorb oils from the seals and appear yellow in color.
Underneath this thick “white” fur is a black skin layer with four and a half inches of fat below that.
Polar bear skin is black underneath the transparent guard hairs. Brad Josephs photo.
When a polar bear is on land or on the sea ice surface the thick fur coat is what insulates the bear from the cold. However, when polar bears are swimming in water, the thick fat layer is what protects them from the frigid cold. Wet fur is not a good insulator and for this reason mother polar bears tend to keep their cubs out of the water as much as possible. The young bears have not built up the protective fat layer yet. Their fur however is enough to survive the cool spring temperatures.
Mother polar bears avoid having their cubs swim in the ocean until they have the fat reserves to protect them. Jonathan Hayward photo.
Another unique characteristic that allows polar bears to keep warm and exude a whitish glow is luminescence. The insides of these transparent guard hairs have tiny bumps that scatter light and create a greater surface for the light across the animals body. The outside of the hairs also collect salt particles from the ocean and act in the same way to refract or scatter the light. Both of these processes cause an overall glow of white in appearance.
