Deep hibernators also show a marked drop in heart rate, and are slow to wake up when disturbed. Only pregnant female polar bears hibernate. Polar bears aren't deep hibernators, but enter a state of carnivore lethargy. Though hibernating females sleep soundly, they're easily and quickly aroused. Unlike most other hibernators, female polar bears give birth while hibernating.
Scientists use radio collars to track the movements of polar bears.
Once a polar bear is fitted with a radio collar, the collar sends signals to a receiving station via satellite. Scientists can enter the data into a computer program that plots the polar bear's path. Only female polar bears can be tracked using radio collars. Male polar bears have necks wider than their heads, and the collars simply fall off. The movements of polar bears can also be studied by following their tracks in the snow, usually by aircraft.