The Pacific white-sided dolphin (scientific name: Lagenorhynchus obliquidens) is a marine mamal within the porpoise family of Cetaceans found in the northen Pacific Ocean.  This cetacean is also known by the common names Pacific white-striped dolphin, Pacific striped dolphin, Pacific white-sided dolphin, Striped porpoise, Hookfin porpoise, Lag, and Striped dolphin.

. Pacific white-sided dolphins (Lagenorhynchus obliquidens). Source NOAA National Marine Fisheries Service

Size comparison of an average human and a Pacific white-sided dolphin (Lagenorhynchus obliquidens). Source: Chris Huh

Conservation Status Least Concern

Scientific Classification Kingdom: Anamalia (Animals) Phylum:--- Chordata Class:------ Mammalia (Mammals) Order:-------- Cetacea (Cetaceans) Family:-------- Delphinidae (Porpoise) Genus:----------Lagenodelphis Species:----------- Lagenorhynchus obliquidens Gill, 1865

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 centimeters. Their coloration is one of the species 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. 

Reproduction

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. 

Lifespan

Maximum longevity in captivity has been recorded as 46 years (captivity); furthermore, one wild born specimen was about 36-37 years old when it died in captivity.

Behavior

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

Members of this species are often seen swimming with seals and sea lions, and sometimes with other cetaceans, especially the Northern right whale dolphin, perhaps because they are all pursuing the same prey.

Distribution

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. 

Habitat

Lagenorhynchus obliquidens is usually found in deep waters up to 160 kilometers (100 miles ) offshore. There appear to be local migrations inshore in the winter months. 

Predation

Before the United Nations established a moratorium on the use of high seas drift nets in 1993, Pacific white-sided dolphins were frequently caught in the nets of Japanese and Korean squid fisheries. Today the species is better protected, and the total North Pacific population is estimated to approach one million.

Food habits

Pacific white-sided dolphins consume fish that live in large schools, such as anchovies, herring, smelt, capelin and mackerel. This cetacean feeds in groups of ten to twenty dolphins, each adult eating about nine kilograms (20 lbs ) of food each day. 

Conservation status

IUCN Red list: Least concern.

References and Further reading

• Encyclopedia of Life. 2010. Contributors: Katie Kiehl, Animal Diversity Web, Smithsonian
• IUCN Red List: Lagenorhynchus obliquidens
• Banks, R. C., R. W. McDiarmid, A. L. Gardner, and W. C. Starnes. 2003. Checklist of Vertebrates of the United States, the U.S. Territories, and Canada
• Banks, R. C., R. W. McDiarmid, and A. L. Gardner. 1987. Checklist of Vertebrates of the United States, the U.S. Territories, and Canada. Resource Publication, no. 166. 79
• Don Wilson and Sue Ruff (1999) The Smithsonian Book of North American Mammals. Smithsonian Books: Washington.
• Foster, L. 1948. The World's Whales. London: Hart-Davis and MacGibbon.
• Gill, 1865. Proceedings of the Academy of Natural Sciences of Philadelphia, 17:177.
• IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
• Leatherwood, S., R. Reeves. 1983. Whales and Dolphins. San Francisco: Sierra Club Books.
• Mead, James G., and Robert L. Brownell, Jr. / Wilson, Don E., and DeeAnn M. Reeder, eds. 2005. Order Cetacea. Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vol. 1. 723-743
• Perrin, W. (2010). Lagenorhynchus obliquidens Gill, 1865. In: Perrin, W.F. World Cetacea Database. Accessed through: Perrin, W.F. World Cetacea Database
• Rice, Dale W. 1998. Marine Mammals of the World: Systematics and Distribution. Special Publications of the Society for Marine Mammals, no. 4. ix + 231
• Richard Weigl (2005) Longevity of Mammals in Captivity; from the Living Collections of the World. Kleine Senckenberg-Reihe 48: Stuttgart.
• UNESCO-IOC Register of Marine Organisms
• Watson, L. 1981. Sea Guide to Whales of the World. London: Hutchinson.
• Wilson, Don E., and DeeAnn M. Reeder, eds. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference, 2nd ed., 3rd printing. xviii + 1207
• Wilson, Don E., and F. Russell Cole. 2000. Common Names of Mammals of the World. xiv + 204
• Wilson, Don E., and Sue Ruff, eds. 1999. The Smithsonian Book of North American Mammals. xxv + 750