Harbor Seal
Phoca vitulina
Class:  Mammalia    Order:  Carnivora    Family:  Phocidae

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Marine Mammal Links
For a list of some of our favorite marine mammal (and California wildlife) sites, see below.

Harbor seals are widely distributed throughout temperate and subarctic waters of the northern hemisphere.  The San Francisco Bay harbor seals are taxonomically classified as Phoca vitulina richardii; P.v. richardii ranges along the Pacific coast of North America from Alaska to Baja California, Mexico ( Reeves et al., 1992 ).  In the United States, harbor seals (like all marine mammals) are protected under the Marine Mammal Protection Act of 1972.

There are variations in coat color in harbor seals. Coat color can range from nearly white with dark spots, to black or dark brown with white rings.  In the San Francisco Bay, "red coat" harbor seals are commonly seen.   This red coloration of the coat results from iron oxide precipitates deposited on the hair.  Allen et al. (1993) report a higher occurrence of red coats in the SF Bay than in any other harbor seal population in the world, ranging up to 40% of seals in the Bay.

Harbor seals are somewhat dimorphic, with adult males slightly larger (1.4 - 1.9 meters long, and weighing up to 140 kg); adult females range in size from 1.2 - 1.7 meters long, up to 80 kg in weight.  Seals are reported to live up to 30 years in the wild (Reeves et al., 1992; Le Boeuf and Bonnel, 1980 ).

Harbor seals are highly opportunistic feeders.  Their diet reflects regional and seasonal variations in prey availability, and include a variety of fishes, cephalopods, mollusks and crustaceans.  They generally feed close to shore or in shallow waters, and may forage at specific, preferred sites (Iverson et al., 1997 ).  Seals have been observed feeding during both the day and night ( Haaker et al., 1984 ).  In the S.F. Bay, an introduced species of fish (the yellowfin goby, Acanthogobius flavimanus) was found to constitute greater than 54% of the prey items found in the stomachs of South Bay seals ( Torok, 1994 ).  Pacific herring (Clupea pallasi) are also a favorite prey of S.F. Bay seals, at certain times of the year.  Analyses of stomach contents of seals living near a salmon fishery on the lower Klamath River, California, have shown that salmon comprise only a small percentage of the diet (Stanley and Shaffer, 1995) , and on the Russian River, there was evidence of seals feeding primarily on lamprey (Hansen 1995).
 

Seals haul out for a number of reasons, including resting, thermoregulating, giving birth, nursing, molting, and facilitating digestion. Haul out sites are generally characterized by environmental features such as easy access to the water, low profile substrate, low human disturbance, and proximity to abundant prey sources.  Site fidelity has been reported (Thompson et al., 1989 ; Yochem et al, 1987 ; Allen, 1988).

Diurnal cycles, tide state and height, and disturbance levels all appear to play a role in the number of seals present on the haul out.  Disturbance caused by human activity can have a major effect on haul out numbers (Pauli and Terhune, 1987 ); severe disturbance may ultimately lead to abandonment of a haul out site (Allen, 1991 ).

While some haul outs are used mainly for resting, certain haul outs are important rookeries for harbor seals.  In the S.F. Bay, the pupping season begins in late March and peaks in the first half of May.  Harbor seals mate in the water, but give birth in the intertidal zone, on land (Newby, 1973 ) and in water (Venables and Venables, 1955 ).  Newborn pups are able to vocalize and swim almost immediately after birth (Newby, 1966, 1973 ).  Nursing lasts about a month; mothers will remain fairly close to their pup during this time, unless disturbed.  Pup abandonment can occur if human disturbance levels are high in the area.
 
 
 

The Seal Conservation Society - This site has great pinniped species information pages, complete with photos, as well as an impressive compilation of links to marine web sites of every description.

The Ocean Conservancy   - This site (formerly the Center for Marine Conservation) will keep you up to date on a wide range of environmental issues involving marine species and the marine environment.  Check out the links to their member magazine, Blue Planet , and their " Get Involved " page for ideas on ways you can help.

The Marine Mammal Center - Located in Sausalito, CA, offers information on education programs, volunteer opportunities, and lots of information on and photos of marine mammal rescue work.  This site is also a good one to check for news and updates on recent marine mammal happenings, like the recent grey whale strandings along the coast of California, and more.  Great link for information on * what to do if you find a stranded marine mammal *

The Monterey Bay Aquarium - Behind the scenes at one of the world's top aquariums, includes info on education programs/teacher workshops and volunteer opportunities.

WhaleNet - This site is a great resource for students and teachers interested in learning more about marine ecosystems and research.  Their satellite tracking page is an excellent introduction to this type of research, complete with real data to explore!  Check out "Lucky's" page .

Romberg-Tiburon Center - SFSU - SFSU's San Francisco Bay (and beyond) research facility; includes description of various SF Bay research projects.

Scripps Institute of Oceanography - UCSD - Includes a description of this premier oceanographic institution, as well as information on publications, photos, research, and careers in the marine sciences.

NOAA Fisheries/The National Marine Fisheries Service - This is the agency to which we report our findings on the S.F. Bay seals; also check out the NOAA Education resources link for lots of educational and fun stuff...

NOAA Fisheries - Viewing Protected Marine Species in the Wild - NMFS has put together a helpful site for those of us interested in viewing marine life in the wild, discusses the guidelines involved and the potential consequences to the animals themselves.  This page also has a list of other marine sites, and sites that provide information on ways that you can help marine life.

The National Marine Fisheries Service - Southwest Region - This division of NMFS is responsible for management and conservation of living marine resources off the California coast (and over 1.3 millions miles of Pacific Ocean!)

NOAA Fisheries - Protected Resources Division -  Great source of information on protected and endangered marine species, including endangered marine mammals, policy issues, and more.

The Marine Mammal Commission - An independent agency of the U.S. Government, the Marine Mammal Commission was created "to provide independent oversight of the marine mammal conservation policies and programs being carried out by the federal regulatory agencies."  Great source for info on U.S. legislation involving marine mammals.

The Society for Marine Mammalogy - Promotes marine mammal science education through dissemination of information, scientific meetings, scholarships, etc.  Includes a link to "Marine Mammal Science," one of the premier publications about marine mammal research conducted in the U.S. and worldwide.

Long Marine Lab - UCSC - Includes description of various marine mammal research being done at the University of California, Santa Cruz, on marine mammal diving physiology, pinniped cognition, and more.  Also includes info and links on research on many marine species, including great white sharks.

Moss Landing Marine Labs - CSU - A marine research and education facility of the California State University system (which includes SFSU).

The National Park Service ~ Park Net - A great guide to the U.S. National Parks!  Includes "Nature Net," with information on and photos of wildlife and plants found in the parks.

U.S. Fish and Wildlife Service - Coastal Conservation Programs - Information on habitat conservation of coastal areas.  The San Francisco Bay is one of 11 high priority coastal ecosystems located in the U.S.

The Don Edwards San Francisco Bay National Wildlife Refuge  -  Located in Newark, CA, the refuge is a great place to visit to learn about Bay wetland ecology.  Their web page has many links to explore, listing a number of organizations that work to protect the marine ecosystem of the San Francisco Bay, and the wetlands that are found on the shoreline.

California Department of Fish and Game - Includes information on fishing, wildlife legislation, endangered species, etc. in California.  Check out "Just 4 Kids," a great page with lots of activities and links for kids!
 

References:
Allen, S.G. (1991) Harbor seal habitat restoration at Strawberry Spit, S.F. Bay. Point Reyes Bird Observatory Report PB91-212332/GAR. 47 pp.

Allen, S.G., Stephenson, M., Risebrough, R.W., Fancher, L., Schiller, A., and Smith, D. (1993)  Red-pelaged harbor seals of the San Francisco Bay region. J. Mammalogy 74(3):  588-593

Haaker, P.L., Parker, D.O., and Henderson, K.C. (1984) Observations of harbor seal, Phoca vitulina richardsii, feeding in southern California waters.  Bull. South Calif. Acad. Sci. 83(3): 152-153.

Iverson, S.J., Frost, K.J., and Lowry, LF.  (1997) Fatty acid signatures reveal fine scale structure of foraging distribution of harbor seals and their prey in Prince William Sound, Alaska.  Marine Ecology Progress Series 151 (1-3):  255-271.

Le Boeuf, B.J. and Bonnel, M.L. (1980) Pinnipeds of the California islands; abundance and distribution.  Pages 475-493 in Power, P.M. (ed) The California islands:  proceedings of a multidisciplinary symposium.  Santa Barbara, CA:  Haagan printing.

Newby, T.C. (1973) Observations on the breeding behavior of the harbour seal in the State of Washington.  J. Mammalogy. 54:  540-543.

Newby, T.C (1966) Viability of premature fetal harbor seal.  Murrelet 47: 46.

Pauli, B.D. and Terhune, J.M. (1987) Tidal and temporal interaction on harbour seal haulout patterns. Aquatic Mammals 13 (3): 93-95.

Reeves, R.S., Stewart, B.S., and Leatherwood, S. (1992) Sierra Club Handbook of Seals of Sirenians.  San Francisco, CA:  Sierra Club Books.

Stanley, W.T.  and Shaffer, K.E. (1995) Harbor seal (Phoca vitulina) predation on seined salmonids in the lower Klamath River, California.  Mar. Mamm. Sci. 11(3):  376-385.

Thompson, P.M., Fedak, M.A., McConnell, B.J., and Nicholas, K.S. (1989) Seasonal and sex-related variation in the activity patterns of common seals (Phoca vitulina).  J. Appl. Ecol. 26: 521-535.

Torok, M.L. (1994) Movements, daily activity patterns, dive behavior, and food habits of the harbor seals (Phoca vitulina richardsii ) in the San Francisco Bay, California.  M.S. Thesis, California State University, Stanislaus.  88 pp.

Venables, U.M. and Venables, L.S.V. (1955) Observations on a breeding colony of the seal Phoca vitulina in Shetland.  Proc. Zool. Soc. Lond. 125:  521-532.

Yochem, P.K., Stewart, B.S., DeLong, R.L., and DeMaster, D.P. (1987) Diel haul out patterns and site fidelity of harbor seals (Phoca vitulina richardsii) on San Miguel Island, California, in autumn.  Mar. Mamm. Sci.  3(4):  323-332.