Harbor seals do not appear to make long annual migrations like some species of marine mammals. However, considerable local movements occur. As more seals are being satellite-tagged, much more information is becoming available about winter and summer movements. They are covered with short, stiff, bristle-like hair. Harbor seals molt annually, usually in late summer.
Harbor seals are well adapted to life in the sea.
Harbor seals are graceful and efficient swimmers as they use their hind flippers for propulsion and foreflippers as rudders. Movement on land, however, is slow and laborious. The young pups are able to swim almost immediately after birth. They normally remain with their mothers about one month, after which they are weaned and separate from their mother. At that time over half their body weight may consist of fat, providing them a head start on self-sufficiency.