What adaptations for economical use of heat have developed in the process of evolution in a bear in the Arctic?

In the process of evolution, this powerful super predator has formed a fairly large subcutaneous layer of fiber, of course, it helps him to survive in such harsh conditions. Also, in the process of evolution, this beast has a rather unusual wool structure. It seems to consist of hollow tubes. This massive animal can reach speeds of up to forty kilometers per hour, which helps him a lot in hunting. Despite its harsh appearance, the polar bear is a rather agile and agile predator.