What adaptation do polar bears use to maintain internal homeostasis in cold temperatures?

Polar bears have developed several adaptations to maintain internal homeostasis in the extreme cold temperatures of their arctic habitat. One of the most important adaptations is their thick fur, which provides excellent insulation against the cold. Each hair shaft is hollow, trapping heat close to the body. Beneath the fur, polar bears have a layer of fat, which can be several inches thick, that insulates them further from the cold and also serves as an energy reserve during times when food may be scarce.

Another adaptation is their black skin, which absorbs heat from the sun efficiently, despite being covered by their translucent fur. Additionally, their large size and compact body shape minimize the surface area exposed to the cold relative to their volume, reducing heat loss. Their extremities, such as ears and tail, are small and rounded to minimize heat loss as well. Polar bears are also extremely efficient at conserving energy. They are slow and methodical in their movements unless actively hunting, which reduces the amount of energy they expend and thus the amount of heat they need to produce to stay warm.