What color is a polar bear’s “overcoat” of guard hairs?
The polar bear is a large ursine which lives in the Arctic region. Although it has black skin under its coat, it is nevertheless often referred to as a “white bear” or “northern bear”. These bears are strong and fast, and can run as fast as 25 miles (40 km) an hour for short distances.
Although polar bears appear to be white or off-white, their stiff outer “guard hairs” actually contain no white pigment. Their warm coat is made up of two layers: dense underfur and an outer layer of guard hairs, which appear white or tan but are actually translucent. Each hair shaft is transparent and has a hollow core that scatters and reflects visible light.
The polar bear is an excellent swimmer whose diet consists primarily of seals, fish and the occasional berry. In addition to 2 layers of fur, a thick layer of fat helps keep the bears warm while hunting. In the water, they rely more on their fat than their fur to keep out the cold; wet fur is a poor insulator.
A polar bear’s body fat can be as much as 4.49 inches (11.4 cm) thick. Polar bears are usually 3.5 to 5 feet (1 to 1.5 meters) tall at the shoulder on all fours, but an adult male may reach more than 10 feet (3 m) when standing on its hind legs, according to Polar Bears International.
Polar bears look whitest when they are clean, have recently molted (lost and replaced their fur), and are in high-angle sunlight. Sometimes the bears look yellow or light tan because of oils that accumulate in their fur from eating seals.