What color is a polar bear's skin underneath its white fur?

Beneath the iconic white coat of a polar bear lies a surprising secret: its skin is actually black. This dark pigmentation is a crucial adaptation for survival in the harsh Arctic environment. The primary reason for black skin is its exceptional ability to absorb heat from the sun. In a landscape of ice and snow, every bit of warmth is vital, and the black skin acts like a solar panel, drawing in and retaining heat to help regulate the bear (Review)'s body temperature. This is especially important given that sunlight in the Arctic is intensified when reflected off the snow and ice.

While the skin is black, the polar bear's fur is not truly white. Instead, each individual hair shaft is transparent and hollow. These hollow hairs trap air, and it's the scattering and reflection of visible light by these transparent hairs that makes the fur appear white to our eyes, much like how snow appears white. This optical illusion provides excellent camouflage, allowing polar bears to blend seamlessly with their snowy surroundings, which is essential for stalking their prey, primarily seals.

The combination of black skin and specialized fur creates an incredibly efficient insulation system. The fur's two layers, a thick undercoat and longer guard hairs, work together to prevent heat loss. The guard hairs are also water-repellent, allowing the bear to easily shake off water after a swim, which is important since wet fur is a poor insulator. This remarkable design allows polar bears to maintain a core body temperature of about 36.9 °C (98.4 °F) even in temperatures that can plummet to -40°C (-40°F) or lower. Their black skin also contains a high concentration of melanin, which helps protect them from the sun's harmful UV radiation, which is particularly intense in the reflective Arctic environment.