The first few weeks of life the cubs depend on three things for survival. Their den is for protection and the den also provides a means of conservation of the mother’s heat and slows her metabolism to reserve her milk supply. Their mother's warmth sense the cubs are born with little insulation. The female has crevices that the cubs can get the warmth. Of course, their mother's rich milk has the consistency of cream. The milk has a taste of cod liver and smells of seals or fish. The milk of a polar bear is richer then whale milk and has more protein then seal milk.
The birth weight of cub polar bear is less than a pound and can fit into the front paw of their mother. It takes about ninety days for a cub to weigh about twenty-five pounds. At this time, the mother polar bear will break the den providing the weather conditions are right and the cubs are healthy. Cubs remain in the den for about a week after it is opened however; their mother will enjoy the outside. She will sun herself, sniff for grass or flowers, and roll in fresh snow. Once the cubs do venture out, they are unable to travel for several weeks. Cubs will lie on there mothers belly to nurse while their mother sits back and puts her head back and seems to slightly move back and forth as if to rock the cubs. Being out of the den makes this an easy position for the mother to be in while the cub's nurse.
The mother polar bear will take a nap during the day during their travel to the ocean for their food supply. This trip may only be a day in travel or can be as far as a week away from the ocean. While mother rests, the cubs will play. They will grab snow and toss it; grab blocks of ice and move them about, or wrestle each other in the snow. Their playfulness is a way they develop many skills they will need when they are old enough to leave the den. The skills that are learned are communications and socialization, and they develop their strength and coordination. This play/learning technique will go on for as long as two years.
When the cubs reach a beginning point of their strength and coordination, and when they are able to walk well and respond to their mother's motion and sound commands such as stay or come, they are ready to leave their mother and den. A new life will be started for the cubs as young adult polar bears and they will be on their own.