Lagenorhynchus obliquidensPacific white-sided dolphin

Geographic Range

Pacific white-sided dolphins have a primarily temperate distribution, remaining north of the tropics and south of the colder waters caused by arctic currents. Their range is from the Aleutian Islands through the Gulf of Alaska to the tip of Baja California in the eastern Pacific; and from Japan to the Kuril Islnads in the western Pacific.


They are usually seen in deep waters up to 160 km (100 miles ) offshore. There seem to be local migrations inshore in the winter months.

Physical Description

Pacific white-sided dolphins have torpedo-shaped bodies which help them move quickly through water. Body length of Pacific white-sided dolphins ranges from 150 to 310 cm. Their coloration is one of their most distinguishing features, they are black or dark gray on the dorsal surface with a white underside, and have bicolored fins and flippers. This coloration is believed to act as a form of camouflage in their aquatic environment.

  • Range mass
    82 to 124 kg
    180.62 to 273.13 lb


Pods are made up of one dominant male and a number of other males and females. The dominant male mates with reproductively available females.

Female Pacific white-sided dolphins reach sexual maturity around 5-6 years of age, males are sexually mature at 8-10 years. Generally breeding occurs in the summer or fall, and gestation lasts approximately 11-12 months. Females give brith to a single calf, which is almost 3 feet long and can weigh up to 14 pounds.

  • Breeding season
    Generally breeding occurs in the summer or fall.
  • Average number of offspring
  • Average number of offspring
  • Range gestation period
    11 to 12 months
  • Range age at sexual or reproductive maturity (female)
    5 to 6 years
  • Range age at sexual or reproductive maturity (male)
    8 to 10 years



Pacific white-sided dolphins are highly gregarious, sometimes seen in schools of 1000 or more. It is more common to find them in groups of 50. When a group member is ill or hurt, other members of the group will seldom leave their side.

Communication and Perception

Food Habits

Pacific white-sided dolphins eat fish that live in large schools, such as anchovies, herring, smelt, capelin, and mackerel. They feed in groups of 10-20 dolphins, each adult eating about 9 kilograms (20 lbs ) of food each day.

  • Animal Foods
  • fish

Conservation Status

Pacific white-sided dolphins are not considered to be endangered. A recent estimate of the population of these mammals in the central North Pacific ranged between a minimum of about 500,000, to a maximum of 930,000. Therefore there is not any immediate danger for the extiction of these animals. They are hunted by Japanese coastal fishermen in the East China and Japan seas and taken accidentally in the North Pacific purse-seine fishery.


Katie Kiehl (author), Michigan State University, Cynthia Sims Parr (editor), University of Michigan-Ann Arbor.


Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


an animal that mainly eats fish


having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Foster, L. 1948. The World's Whales. London: Hart-Davis and MacGibbon.

Leatherwood, S., R. Reeves. 1983. Whales and Dolphins. San Francisco: Sierra Club Books.

Watson, L. 1981. Sea Guide to Whales of the World. London: Hutchinson.