Harbor seals can be up to 6 feet long and weigh up to 375 pounds, males characteristically being slightly larger than females. The rounded, fusiform body is covered by a coat made of thick, short hairs that range from nearly white with dark spots to black or dark brown with white rings. The dorsal surface is usually more densely covered with spots or rings than the ventral surface.
The limbs of the harbor seal have been modified into flippers. The foreflippers (pectoral flippers) are composed of 5 digits of similar length and webbed together. Claws on the foreflippers are used for scratching, grooming, and defense. The hind flippers also have 5 digits; however, the first and fifth digits are long and stout, while the middle digits are shorter and thinner. The hind flippers propel the seal forward by moving side to side. On land, the harbor seal moves by undulating in a caterpillar-like motion.
Range mass: 50 to 170 kg.
Range length: 2 (high) m.
Sexual Dimorphism: male larger
Average basal metabolic rate: 73.29 W.