Male and female polar bears become sexually mature at around four or five years of age, however, most males won’t breed until they are between eight and 10 years old. Mating takes place in the spring, but the embryo does not begin to grow until between September and October. At this time, the female will excavate a birthing den, ideally in a few metres into a snowdrift. The den will maintain a temperature close to zero degrees Celsius regardless of the outside temperature, thanks to the insulation provided by the snow. After around two months of gestation, one or two cubs are born, with twins being most common. At birth, cubs are almost bald and weigh less than one kilogram, but they grow rapidly because of their mother’s rich milk, which is 31 per cent fat. Mother polar bears fast while in the den – all her energy and fat stores are used to feed and raise her cubs.

The family will emerge from the den between the end of February and early April, but will stay near it for a few weeks to exercise and get used to the cold. They will then begin their trek toward the sea and ice edge, where the mother can finally feed and teach her cubs how to hunt. Cubs will continue to nurse for about two years, while also eating meat provided by their mother. Polar bears feed primarily on ringed seals, but they also eat bearded seals, harp seals, hooded seals and harbour seals, and will occasionally hunt smaller walruses, beluga whales and narwhals. Polar bears are dependent on sea ice to catch seals as they are most efficient as ambush hunters. They catch seals by waiting for them to surface at their breathing holes, stalking them sunbathing on the sea ice and by breaking into the birthing chambers of ringed seals.