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Marine Mammals
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 Harbor Seal

Image Credit: NOAA

 Harbor Seal
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 National Marine Sanctuaries Where Harbor Seals Can Be Found:
  Olympic Coast
Cordell Bank
Gulf of the Farallones
Monterey Bay
Stellwagen Bank
Gray's Reef

 Related Environmental Issues:
  Point Source - Oil Spills
Non-Point Source - Runoff
Habitat Loss
Climate Change

 Activities Related to Harbor Seals:

 Other Resources Related to Harbor Seals:

Scientific Name: Phoca vitulina

Category: Pinnipeds

The harbor seal is also called the "common seal" and lives in the waters off the coast of North America in the Atlantic and Pacific Oceans. Off the coast of Europe, they are also found in the Baltic and North Sea. Seals in the Pacific Ocean, especially those in Alaskan waters, are usually larger than those found in the Atlantic Ocean. The population worldwide is estimated at about a half a million. The female harbor seals live until 30-35 years of age, but the males only live 20-25 years. Scientists say this might be because there is stress and fighting among the males during mating season. Most often the seals live alone, but they sometimes form groups. The Harbor Seal is part of the "true seal" family, as it has no external ears and has short flippers. These short flippers are great for swimming, but make movement on land slow and awkward. The seals may swim short distances for food, but they do not migrate. Scientists have tagged the seals and are tracking them to learn more about their feeding habits. The seals spend about one half of their time on land and one half in the water. They are even known to sleep in the water.

The males usually weigh 170 kg (350 lbs) and can grow up to 2m (6 feet) in length. The females are smaller than the males. The harbor seal body is shaped like a cylinder and covered with short bristle-like hairs that are silver, gray, black or brown. Each seal has a pattern of unique spots covering the top of its body that is darker or lighter than the rest of its fur. They have short tails, flippers, and a V-shaped nostril that is unique to the Harbor Seal. The flippers have claws that can be used for defense or scratching themselves. They have no ears, but do have ear slits behind their eyes. They can swim up to 15 miles per hour.

As the breeding season approaches in the spring and the summer, males fight over the females. During mating season, many males are seen with neck wounds. The strongest of the males mate with the females underwater and 11 months later the mothers give birth to one pup. A few hours after the pups are born, they can swim and even dive. They weigh about 16kg (30 lbs) at birth and already have a layer of blubber to keep themselves warm. The Harbor Seal pups feed on their mothers milk and grow rapidly. After about 4-6 weeks, they have doubled in size and are ready to be on their own. After the pup is weaned, the female mates again. After breeding, usually in late summer, the seals shed their fur. This process is called molting. They live on shore while molting, and then return to the ocean. The seals return to the same breeding grounds every year.

Harbor seals look for places to feed that are near rocks, where they can be protected from predators like the great white shark and the killer whale. The pups are vulnerable, even on shore where they are often attacked by coyotes and bobcats. The seals feed along rocky coasts, rivers, and beaches, in both fresh and salt water. There have been recent sightings of them in the harbors of New York and Boston. The seals tend to hug the coast and are rarely found more than 20km from shore. The harbor seal eats fish such as cod, sea bass, whiting, herring, and anchovies. Sometimes they also eat shrimp and squid. The seals tear their food into chunks or swallow the food whole instead of chewing it. In pursuit of food, they can dive for as long as ten minutes and go down as far as 450m (1500 feet). They have very hard molars which they use to crush the shells of their food. Many times after eating, large groups leave the water together to sit on rocks and this is called a "haul out". The harbor seal usually do a daily haul out. Sometimes it is for sunning themselves, resting, social activity or giving birth. If they stayed in cold water all the time, they would die. Their blubber is not thick enough to maintain their body temperature in the cold water. Haul outs usually occur at low tide. Resting on rocks is also a way to escape predators. When the seals are threatened, they growl and snort, wave a flipper and sometimes headbutt. Then they slip back into the ocean. They only make sounds when they are threatened.

The life cycle of the harbor seal is being challenged in many different ways. The seals are found in the bycatch of commercial fishing nets. Boats sometimes run them over. Oil spills and pesticides kill significant number of seals, and humans also interfere with them. This happens when people find Harbor Seal pups alone on beaches and bring them to rehabilitation centers. The pups have not been abandoned as the people think. Their mother is merely swimming offshore and the pup should be left on the beach. If they are left alone, the mother returns and feeds the pups. At rehabilitation centers, the pups are cared for, but they miss out on their mothers milk. Many times this threatens their survival.

In the United States, the Marine Mammal Protection Act of 1972 makes it illegal to kill any marine mammal including seals. However, the native people, especially in Alaska, are allowed by law to hunt small numbers of them for their subsistence living. The native culture is built on the use of seal fur, meat and oil. For the last several decades, the seal population in the Alaskan waters has been decreasing due to illegal hunting and native catch. In warmer climates, aquariums keep harbor seals as they are popular with tourists. In San Francisco, the harbor seals have taken up residence on Pier 39 at Fishermans Wharf where they accommodate tourists by hauling out every day so the tourists can watch them.

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