Pair of harbor seals (Phoca vitulina) hauled out on rocks, Southeast Alaska, USA.
Harbor seals (Phoca vitulina), are “true seals” of the Phocidae family, also sometimes called “common” or “hair” seals. They are covered with short, stiff, bristle-like hair. Coloration varies, but two basic patterns occur: light gray sides and belly with dark blotches or spots, or a dark background with light rings. They can be distinguished from other pinnipeds, such as fur seals and sea lions, by the absence of external ear flaps; only a small hole (the external pinnae, or opening to the ear canal) is visible on either side of their head. When on land, harbor seals move awkwardly by undulating in a caterpillar-like motion because their pelvic bones are fused, preventing them from moving their hind flippers under their pelvis to walk. In the water they are graceful and efficient swimmers, using their fore flippers as rudders and their hind flippers for propulsion by clasping both hind flippers together, splaying webbed toes and moving the large hind flippers side to side.
Harbor seals weigh about 24 pounds (11 kg) at birth and gain weight rapidly during a month-long suckling period; perhaps doubling their weight. They can reach five to six feet (1.5-1.8 meters) in length. Average weight for adults is about 180 pounds (82 kg); males are somewhat larger than females and can weigh up to 285 pounds (129 kg).