Harbor Seals

There are five subspecies of Harbor Seal (Phoca vitulina) generally recognized, and the estimated total worldwide population is between 350,000 and 500,000. 

Harbor Seals have the largest geographical range of any pinniped, encompassing coastal areas of the east and west Pacific and Atlantic Oceans in the Northern Hemisphere.

In the U.S. Harbor Seals were once commercially harvested for their skin and meat, which caused a rapid decline in their population throughout the nineteenth century. Another decline occurred, along the west coast of the U.S. during the 1940’s and 1950’s, due to bounty hunting. 

Today Harbor Seals, just like all marine mammals in the United States, are protected by the Marine Mammal Protection Act (MMPA) which was passed in 1972. The MMPA prohibits, with certain exceptions, the take of marine mammals in U.S. waters and by U.S. citizens on the high seas, and the importation of marine mammal and marine mammal products into the U.S. 

Harbor Seals are still hunted to a small extent by Native peoples which results in minimal impact to the arctic populations. Since the MMPA was enacted, Harbor Seal populations have rebounded and are now stable in most areas throughout its North American range.   

Did you know? Their scientific name translates to sea calf or sea dog.

Harbor Seal pic 1

Description

Harbor Seals have spotted coats in a variety of shades from white to silver-gray to black or dark brown. They are quite stocky and can grow to be 6 feet long and weigh up to 300 pounds, with males being slightly larger than females.    

Harbor Seals are phocid seals or “true seals” meaning they do not have external ear flaps and their front limbs are shortened, which limits their movements on land.

In the water they use their hind flippers for propulsion, while on land their method of locomotion is caterpillar-like movement utilizing their fore flippers for momentum.         

Did you know? They have large eyes to see in dark, deep water and they have long necks which can shoot out quickly to catch fish while swimming.

Harbor Seal pic 2

Ecology

Habitat:
Harbor Seals are non-migratory; they breed and feed in the same area throughout the year. They live in temperate coastal habitats.  

Haul Outs:
Unlike other marine mammals that are completely dependent on being in water, Harbor Seals spend time on land.

Harbor seals use rocks, reefs, beaches, mudflats, sand bars, log-booms, docks and drifting glacial ice as haul outs. Although, they prefer gently sloped beaches and low lying flat spots. They use these haul outs to rest, molt, thermal regulate, socialize, give birth and avoid predators.        

Development and Family Structure

Harbor Seals give birth to one pup during the spring and summer. The pupping season varies with latitude, and along the Washington coast Harbor Seals pup between mid-April and October. 

Females nurse their pups for an average of 24 days and during that time pups gain between 1.1 and 1.3 pounds per day. Pups are able to swim minutes after birth and stick very close to mom in the water.

Harbor Seal females fast during the first week of lactation but will then leave their pup during feeding bouts. 

Foraging

Harbor Seals are opportunistic foragers and will switch prey according to annual and seasonal variability. They feed on a variety of prey items including fish, shrimp, small squid and mollusks.   

Did you know? A seal’s whiskers help it hunt and navigate by sensing pressure waves from fish and underwater objects.

Harbor Seal Haul Out pic

Behavior

Harbor Seals tend to haul out in groups of 30 to 80 individuals, although larger groups have been recorded. Some haul out groups may be dominated by one age or sex class. Some groups are mainly mothers and pups while others are adult males or mainly juveniles.

While Harbor Seals are hauled out there is little social interaction, however when they are in the water they often play and roll in the waves together as well as follow each other to feeding sites. 

Harbor Seals are very wary of people while on land and will rush into the water if they are approached too closely. They have also been known to abandon haul outs and pups if disturbed too often.

Did you know? They can dive for three minutes at a time typically, but they can stay under water for as long as 30 minutes and dive as deep as 600 feet.

Harbor Seal pic 4

Living with Harbor Seals

It is quite common to see Harbor Seals hauled out on beaches along the Washington coast. If you happen to see some, do not touch. It is illegal to touch any marine mammal as they are protected by the Marine Mammal Protection Act. However, you may observe seals from more than 100 yards away with binoculars. 

Injured/orphaned seal pups:
If you believe you have found an injured adult, or a pup that has been unattended by its mother for more than 48 hours, contact Sno-King Marine Mammal Response at 206.695.2277 or the NOAA Seal Hotline at 1.866.767.6114.

Harassment:
If you witness anyone harassing a seal or other marine mammal, or allowing their pets to do so, call the NOAA Fisheries Enforcement Hotline at 1.800.853.1964.

References

Department of Ecology, State of Washington. March 9, 2015. Puget Sound Shorelines: Harbor Seal.

Feldhamer G.A., Thompson B.C. & Chapman J.A. (Eds). (2003). Wild Mammals of North America, Biology, Management, and Conservation (2nd ed.). Baltimore MD: The Johns Hopkins University Press. 

The Marine Mammal Center. March 9, 2015. Pacific Harbor Seal.

NOAA Fisheries. March 9, 2015. Harbor Seal.

SEADOC Society. March 9, 2015. Harbor Seal Facts.

Seal Conservation Society. March 9, 2015. Seal Information: Harbor Seal.

Washington Department of Fish and Wildlife. March 9, 2015. WildlifeWatchcams: Harbor Seal. 

Images: Copyright PAWS 2015