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
Grizzly–polar bear hybrid born at Osnabrück Zoo in Osnabrück, Germany, in 2004, and their physical traits are generally an intermediate between the polar bear and the grizzly bear. For example, their bodies are smaller than polar bears, but larger than grizzlies, while their heads fall between the broader grizzly head and the leaner polar bear head. They have long necks like polar bears, but small shoulder humps like grizzlies. The soles of their feet are partially covered in hair; polar bears have hair-covered soles, which act as insulation, and grizzlies have hairless soles. Similarly, the hair of the hybrids exhibits a pattern of