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 formula is Polar bears are superbly insulated by up to of adipose tissue, their hide and their fur; they overheat at temperatures above , and are nearly invisible under infrared photography. Polar bear fur consists of a layer of dense underfur and an outer layer of guard hairs, which appear white to tan but are actually transparent. Two genes that are known to influence melanin production, LYST and AIM1, are both mutated in polar bears, possibly leading to the absence on this pigment in their fur. The guard hair is over most of the body. Polar bears gradually moult from