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 vegetative cover and wind direction to bring them as close to their prey as possible before attacking. Polar bears have been observed to hunt the small Svalbard reindeer ("R. t. platyrhynchus"), which weigh only as adults, as well as the barren-ground caribou ("R. t. groenlandicus"), which is about twice as heavy as that. Adult muskox, which can weigh or more, are a more formidable quarry. Although ungulates are not typical prey, the killing of one during the summer months can greatly increase the odds of survival during that lean period. Like the brown bear, most ungulate prey of polar bears