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.

In the northeast Pacific, they range from Alaska to Baja California, Mexico.

They favor near-shore coastal waters and are often seen at sandy beaches, mudflats, bays, and estuaries.

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.

They are opportunistic feeders, eating sole, flounder, sculpin, hake, cod, herring, octopus, and squid.

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 25 to 30 years.

They are usually found in small groups, but sometimes occur in numbers of up to 500.