ndangered Whales in the Southern California Planning Area
Five of the six endangered whales found in southern California waters are baleen
whales, which feed by filtering their food through fringed baleen plates. The sixth is the
sperm whale, the largest of the toothed whales. Populations of all these species were
sharply reduced by commercial whaling in the nineteenth and twentieth centuries, some to
the verge of extinction. As a result, in 1970, seven species were listed as endangered
under the Endangered Species Act.
The seventh species, the gray whale, has since recovered to what are believed to be
pre-whaling levels and has recently been removed from the List of Endangered and
Threatened Wildlife. The great whales are also protected throughout the world under a
moratorium on commercial whaling implemented by the International Whaling Commission in
1986.
Endangered baleen whales, including the blue, fin, sei, humpback, and right whales, are
distributed worldwide in polar and temperate waters and migrate between warmer waters used
for breeding and calving in winter and high-latitude feeding grounds where food is
plentiful in the summer. The sperm whale is an open-water species and is found mainly in
temperate to tropical waters in both hemispheres.
Although there is some variation among species, the typical baleen whale reproductive
cycle involves about one year of gestation, followed by a 6- to 9-month nursing period.
Females generally calve every 2 to 3 years.
Sperm whale calves are normally born in the summer or fall after a 14- to 15-month
gestation period and are weaned later, at about 2 years of age. Sperm whale females
generally give birth at 3- to 5-year intervals. Most baleen whales feed on a variety of
shrimplike invertebrates, and some species also take small schooling fishes and squid.
Sperm whales are deep divers and feed mainly on large squid and deepwater fishes.
Blue whales are the largest of all animals. They usually reach peak abundance off
southern California in June and are rarely sighted after October. The blue whale migration
pathway through this area generally appears as a broad band along the continental slope
west of the Channel Islands. Commercial whaling reduced the blue whale population
worldwide from an estimated 228,000 to less than 10,000. Currently, the blue whales that
feed off California are believed to number about 2,300, more than recent estimates for the
entire North Pacific population.
Fin Whales, like blue whales, migrate northward from subtropical calving and wintering
grounds to summer feeding grounds in Alaska. In southern California waters, most fin
whales are observed between March and October. The world population of fin whales may have
been as high as 500,000 animals before their exploitation by commercial whalers began. By
1976, when they were protected from commercial harvest, the world fin whale numbers had
declined to an estimated 120,000. Recent estimates for the eastern North Pacific range
between 8,000 and 11,000 animals.
Sei whales are primarily an open-ocean, temperate-water species. In the eastern North
Pacific, sei whales migrate northward from calving and wintering grounds in temperate and
subtropical waters to summer feeding grounds that extend from the Channel Islands to
Alaska. The winter range stretches from southern Mexico to central California, but sei
whales are uncommon in California waters. Sei whale numbers were reduced from an estimated
world population of 256,000 to about 50,000. The North Pacific population is currently
estimated at 7,000 to 13,000 whales.
Humpback whales in the eastern North Pacific range from arctic waters south to
California in the summer. Humpback whales winter and calve in three areas: waters off
Mexico; Hawaii; and the Marianas, Bonin, and Ryukyu Islands and Taiwan in the western
Pacific. In recent years, humpbacks have occurred in increasing numbers off southern
California. The pre-exploitation world population has been estimated at about 115,000
animals. The world population is presently estimated at 10,000 whales, and recent
estimates of the North Pacific population range from 1,200 to 2,100. About 900 humpback
whales forage in California waters.
Northern right whales are the rarest of the endangered whales. In the North Pacific,
the population is currently believed to number 100-200 animals, which is far below the
estimated pre-exploitation size of 15,000. Right whales apparently migrate from
high-latitude feeding grounds toward more temperate waters in the fall and winter. The
location of calving grounds is unknown; summer feeding grounds may generally stretch
across the North Pacific from the latitude of about British Columbia to the Bering Sea.
Sperm whales now number more than 1,000,000 worldwide, down from an estimated
pre-exploitation population of 2,400,000. The eastern North Pacific population is
currently estimated at 550,000 animals, and the species is under consideration for removal
from the List of Threatened and Endangered Species. Sperm whales are primarily a pelagic
species, and are generally in deep waters well offshore. In the North Pacific, females and
juveniles generally remain south of about central Oregon year-round, while adult males
range northward as far as the Bering Sea in summer. Off California, sperm whales are
present in offshore waters year-round.
Selected Reading
Bonnell, M.L., and M.D. Dailey. 1993. Marine mammals of the Southern California Bight.
Pp. 604-681, in, M.D. Dailey, D.J. Reish, and J.W. Anderson (eds.), Ecology of the
Southern California Bight: A Synthesis and Interpretation. University of California,
Berkeley/Los Angeles
Haley, D. (ed.). 1986. Marine mammals of the eastern North Pacific and Arctic waters
(2nd. ed. rev.). Pacific Search Press, Seattle, Washington.
Orr, R.T., and R.C. Helm. 1989. Marine Mammals of California. California Natural
History Guides: 29. University of California Press, Berkeley. 93 pp.
Leatherwood, S., R.R. Reeves, W.F. Perrin, and W.E. Evans. 1982. Whales, Dolphins, and
Porpoises of the Eastern North pacific and Adjacent Arctic Waters: A Guide to Their
Identification. U.S. Department of NOAA Technical Report, NMFS Circular 444. 245 pp.
Ridgway, S.H., and R.J. Harrison (eds.). 1985. Handbook of marine mammals, Vol. 3: The
sirenians and baleen whales. Academic Press, New York.
Watson, L. 1985. Whales of the world: a complete guide to the world's living whales,
dolphins, and porpoises. Hutchinson, London.
For more information
U.S. Department of the Interior
Minerals Management Service
770 Paseo Camarillo
Camarillo, CA 93010
(805) 389-7800
Web Master:
Nollie
Gildow-Owens
Page content last updated 09/20/2006
Page last published 09/20/2006