Sindhuja A

carcasses. In fall, polar bears also gather together in “transition” areas such as southwestern Hudson Bay and Churchill, Canada to wait for the sea ice to form that allows them access to ringed seals swimming beneath the ice. Polar bear territories are vast. Bears closest to the Canadian Arctic Islands have an average range of 19,000–23,000 sq miles (50,000–60,000 sq km), but those closer to the Bering Sea can cover up to 135,000 sq miles (350,000 sq km). Winter births Polar bears give birth to cubs every two to three years —one of the lowest reproductive rates of all mammals. Mating occurs from late March through May, but embryos may not start to develop until fall. Pregnant females must gain about 440 lb (200 kg) extra weight during summer to survive the winter, when they may have to go up to eight months without food. They dig maternity dens mainly in south-facing snowdrifts, where between one and four cubs are born in early winter. Most litters are of twins. The adult female does not hibernate in the truest sense, but maintains a much warmer body temperature to care for her cubs. Even so, she neither eats, urinates, nor defecates during the months she is in the den. Mother and cubs do not emerge from their den until March or early April, when she leads them toward the sea ice in order to hunt.