Porpoise Phocoenoides dalli
Length: 1.8 meters
Weight: 123 kg
Food: squid and school fish
Social Status: Commonly found
in groups of 10 - 20
Sexually mature at about 2 years
annually to 1 calf
Gestation: 10-11 months
Newborn: 95-100 cm long
life expectancy: about 10 years, oldest 22 years.
IUCN Red List Status: Lower
Porpoises have flattened spade-shaped teeth and their forehead is
convex at the tip of the upper jaw. Dolphins have sharp conical
teeth and their forehead is concave at the upper jaw.
Dallís porpoise is a widespread and numerous species in the North
Pacific, and yet much is to be learned about the species. It lives
along the coast and in the open ocean from California to Japan. It
prefers deep canyons in coastal areas and where water is cold. It is
likely that these places have the greatest prey abundance.
porpoises are mostly black in colour with white flanks and white
tipped fins. Young porpoises are grey with white flanks. Reeves et
al.ís (2002) book has excellent illustrations of age classes. Two
types of Dallís porpoise occur - the truei type is found in
the western Pacific off Japan and the dalli type along the
Pacific Coast of North America. The western Pacific form has a white
lateral patch extending to the pectoral fins whereas the white
lateral line on the dalli type reaches only to the mid line
of the dorsal fin.
Estimating the number of Dallís porpoises is difficult because of
their wide ocean going range. Estimates range from several hundred
thousand to 1 million animals but there is not much certainty in
these estimates. Dallís porpoise is often attracted to moving boats
to ride the bow wave and schools of 2 to 12 animals are most common.
are born in June and July, and mating occurs soon after the calves
are born. Calves stay with their mothers until the next calf is
born. They then gather with other immature porpoises and adult males
in the southern part of the range. Dallís porpoises eat deepwater
fish and squid probably at night, and schooling fish such as
herring, anchovy, hake and juvenile rockfish during the day. Orcas
and sharks prey on porpoises. There are excellent photographs of
orcas hunting porpoises on page 19 in Ford et al. (2000) and page
473 in Reeves et al. (2002). Baird et al. (1998) reported the first
hybridization for the species. They found a 60-cm female fetus in a
dead Dall's porpoise in southern British Columbia that was fathered
by a harbour porpoise (Phocoena
Baird, R. W. Pamela M. Willis, Tamara J. Guenther,
Paul J. Wilson and Bradley N. White. 1998.
intergeneric hybrid in the family phocoenidae. Canadian Journal of
Ford, J. K. B., G. M. Ellis and K. C. Balcomb. 2000.
Killer whales. Second ed. University of British Columbia Press,
Murayama, T. and others. 1992. Histological
characteristics and distribution of ganaglion cells in the retinae
of the Dallís porpoise and minke whale. Pp. 137-145 in Marine Mammal
Sensor Systems (JA Thomas et al. eds.). Plenum, New York.
Reeves, R. R., B. Stewart, P. Clapham and J. Powell.
2002. Guide to marine mammals of the world. Alfred A. Knopf, New
Walker, W. A. 1996. Summer feeding habits of Dallís
porpoise Phcoenoides dalli, in the southern Sea of Okhotsk. Marien
Mammal Science 12:167-181.
Wilson, D. E. and S. Ruff (eds). 1999. The
Smithsonian book of mammals. Smithsonian Institution, Washington DC.
(written March 2005)