Polar bear the fourhorn sculpin. With the exception of pregnant females, polar bears are active year-round, although they have a vestigial hibernation induction trigger in their blood. Unlike brown and black bears, polar bears are capable of fasting for up to several months during late summer and early fall, when they cannot hunt for seals because the sea is unfrozen. When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time, as polar bears do not 'hibernate' any time of the year. Being both curious animals and scavengers, polar bears investigate and
Polar bear are poorly understood, as carcasses are rarely found in the species's frigid habitat. In the wild, old polar bears eventually become too weak to catch food, and gradually starve to death. Polar bears injured in fights or accidents may either die from their injuries or become unable to hunt effectively, leading to starvation. The polar bear is the apex predator within its range, and is a keystone species for the Arctic. Several animal species, particularly Arctic foxes ("Vulpes lagopus") and glaucous gulls ("Larus hyperboreus"), routinely scavenge polar bear kills. The relationship between ringed seals and polar bears is so close