Pacific harbor seals have spotted coats in a variety of shades from white or silver-gray to black or dark brown. They reach five to six feet (1.7-1.9 m) in length and weigh up to 300 pounds (140 kg). Males are slightly larger than females. They are true or crawling seals, having no external ear flaps. True seals have small flippers and must move on land by flopping along on their bellies. In San Francisco Bay, many harbor seals are fully or partially reddish in color. This may be caused by an accumulation of trace elements such as iron or selenium in the ocean or a change in the hair follicle.
Pacific harbor seals are found north of the equator in both the Atlantic and Pacific Oceans. In the northeast Pacific, they range from Alaska to Baja California, Mexico. They favor near-shore coastal waters and are often seen on rocky islands, sandy beaches, mudflats, bays, and estuaries.
In California, harbor seal pups are born between February and April and weigh about 20 to 24 pounds at birth. If born prematurely, harbor seals retain a whitish lanugo coat (which is usually lost before birth). A pup can swim at birth and will sometimes ride on its mother's back when tired. Pups make a bleating noise that sounds like "maaaa." After about four weeks, the pups are weaned. Adult females usually mate and give birth every year. They may live for 25 to 30 years.
Pacific harbor seals spend about half their time on land and half in water. They can dive to 1,500 feet (457 m) for up to 40 minutes, although their average dive lasts three to seven minutes and is typically shallow, and they sometimes sleep in the water. They are opportunistic feeders, eating sole, flounder, sculpin, hake, cod, herring, octopus, and squid. While harbor seals swim safely in the surf, they will often curiously watch humans walking on beaches. However, they are wary of people while on land and will rush into the water if approached too closely or disturbed. In fact, if disturbed too often, they have been known to abandon favorite haul-out sites or their pups.
The world wide harbor seal population is estimated to be 500,000 individuals. The portion of that number estimated to live in California was about 34,000 in 2009. They are usually found in small groups, but sometimes occur in numbers of up to 500.
At The Marine Mammal Center
Harbor seals are the third most common patient at The Marine Mammal Center. From mid-February through the end of June, the Center's rescue and rehabilitation work focuses on orphaned harbor seal and elephant seal pups. Spring brings harbor seal colonies to rookery beaches that are accessible to humans. Sometimes a pup and mother become separated due to disturbance by beachgoers. Unfortunately, this severely decreases the pup’s chance for survival. Harbor seal pups are highly susceptible to disease and stress, so they are kept quarantined from other patients and out of public view. Harbor seal colonies in the Bay Area are vulnerable to human disturbance, climate change and human-produced pollutants. Our scientists are involved in collaborative studies that examine health, disease, contaminant levels and post-release survival in this species.