The National History Museum in London made a special about polar bears, explaining how the polar bear fur functions, part of this exhibition is a video:
Asknature also features a great story about the insulating fur of polarbears.
Polar bears living in the Arctic Circle survive in one of the harshest climates in the world. Winter temperatures can fall to -40 °C, but polar bears manage to keep their internal body temperature at a steady 37 °C.
One physical feature that helps the polar bear stay warm is its fur coat. The coat is made up of two distinct layers: a short and dense underfur layer right next to the skin, and an outer layer of longer and coarser guard hairs. The guard hairs are transparent but the polar bear’s coat appears white because the hairs scatter sunlight.
Reed the full story on www.asknature.org . https://asknature.org/strategy/fur-absorbs-infrared-radiation/#.XJNd6ShKiUk