MARINE MAMMAL RESEARCH UNIT - UBC

Pacific white-sided dolphin biology

Pacific White-Sided Dolphin Biology Fast Facts

Common Name:

Pacific white-sided dolphin

Scientific Name:

Lagenorhynchus obliquidens


Habitat/distribution:

Pacific white-sided dolphin are found in both the open-ocean and coastal waters, and are primarily observed in temperate waters of the North Pacific Ocean. In North America, they are seen off the west-coast ranging from California to Alaska and worldwide their habitat includes the southern Bering Sea, the Sea of Japan and the Sea of Okhotsk.


Body size:

Pacific white-sided dolphins weight is estimated to be approximately 300-400 lbs (140-180kg) and their length ranges from 2-2.4m. Males are generally slightly larger than females.


Physical Characteristics:

Pacific white-sided dolphins are very distinct in that their backs are dark grey, their underside is white, and their sides are striped with white or light grey, which gives them their unique name! Their dorsal fin in the middle of their back is quite curved and is bicoloured with dark grey and white/light grey.


Life expectancy:

Pacific white-sided dolphin life expectancy is estimated to be 40 years old.


Behaviour (e.g. sounds, foraging):

This species moves quickly, frequently leaping out of the air and is often seen in large groups. Pacific white-sided dolphins have been observed in groups of thousands of individuals, but average group size ranges from 10 to 100 individuals. In addition to seeing them leap out of the air doing somersaults and flips, they’re also known to approach boats to bow ride or ride in the boat wake.

Pacific white-sided dolphin forage cooperatively as they are known to work as a group to herd fish together. They are also known to frequently interact with other species including resident killer whales, Steller sea lions and porpoise. However, much is still being discovered as to why they interact with these species.


Diet:

Pacific white-sided dolphin are opportunistic feeders, which means that they prey on a diverse number of species, depending on what’s most available! In B.C. waters this species primarily feeds on various salmon species, shrimp, squid and other small schooling fish.


Predators:

Transient killer whales, which eat marine mammals, are Pacific white-sided dolphins largest predator. However, in some parts of their range they are preyed on by large shark species.


Reproduction:

Female Pacific white-sided dolphin reach sexual maturity at approximately 8 years old while males become sexually mature at approximately 10 years old. Mating generally occurs in the spring and fall with births happening in the spring and summer season after a 9-12 month gestation period. Females reproduce on average every 3-5 years.


Population:

There are no current population estimates for Pacific white-sided dolphins. In the early 1990s it was estimated that their entire population consisted of 1,000,000 individuals and the most recent survey in BC, which was published in 2007, estimated that 25,000 individuals live in BC waters.


Conservation status:

COSEWIC currently lists Pacific white-sided dolphin as ‘not at risk’. However, the most current report was produced in 1990. In British Columbia the species is ranked as yellow which is the least risk of being lost. Up until 1993, Pacific white-sided dolphin were severely threatened by fishing gear as thousands were being caught accidentally in large-scale driftnets. However, in 1993 the United Nations banned the use of this type