During mating season, female harp seals form large colonies on floating ice and give birth to young. Older seals return annually to pack ice to molt. They lose their pelts and top layers of skin and grow a new fur coat every year.
Harp seals are sometimes called saddleback seals because of the dark, saddlelike marking on the back and sides of their light yellow or gray bodies of the adults.
Baby seals are born on pack ice floating in the North Atlantic and Arctic Oceans. Harp seal mothers are able to identify their babies by their smell. The pups don't have any blubber at birth, but quickly gain weight nursing on high-fat mother's milk. When the pups reach about 80 pounds (36 kilograms), their mothers stop nursing them. The pups go without food for about six weeks and can lose about half their body weight until they dive in and begin to hunt for themselves. The young seals are famous for their snowy white coats.