in life. Polar bears are usually quiet but do communicate with various sounds and vocalizations. Females communicate with their young with moans and chuffs, and the distress calls of both cubs and subadults consists of bleats. Cubs may hum while nursing. When nervous, bears produce huffs, chuffs and snorts while hisses, growls and roars are signs of aggression. Chemical communication can also be important: bears leave behind their scent in their tracks which allow individuals to keep track of one another in the vast Arctic wilderness. In 1992, a photographer near Churchill took a now widely circulated set of photographs of a polar bear playing with a Canadian Eskimo Dog (Canis familiaris) a tenth of its size. The pair wrestled harmlessly together each afternoon for 10 days in a row for no apparent reason, although the bear may have been trying to demonstrate its friendliness in the hope of sharing the kennel's food. This kind of social interaction is uncommon; it is far more typical for polar bears to behave aggressively towards dogs. Hunting and diet The polar bear is the most carnivorous member of the bear family, and throughout most of its range, its diet primarily consists of ringed (Pusa hispida) and bearded seals (Erignathus barbatus). The Arctic is home to millions of seals, which become prey when they surface in holes in the ice in order to breathe, or when they haul out on the ice to rest. Polar bears hunt primarily at the interface between ice, water, and air; they only rarely catch seals on land or in open water. The polar bear's most common hunting method is called still-hunting: the bear uses its excellent sense of smell to locate a seal breathing hole, and crouches nearby in silence for a seal to appear. The bear may lie in wait for several hours. When the seal exhales, the bear smells its breath, reaches into the hole with a forepaw, and drags it out onto the ice. The polar bear kills the seal by biting its head to crush its skull. The polar bear also hunts by stalking seals resting on the ice: upon spotting a seal, it walks to within , and then crouches. If the seal does not notice, the bear creeps to within of the seal and then suddenly rushes forth to attack. A third hunting method is to raid the birth lairs that female