Pacific white-sided dolphins are medium sized dolphins reaching up to 8 feet (2.5 m) in length. They are considered robust animals, with a large and strongly falcate (curved or hooked) dorsal fin. They have a small and unnoticeable beak, unlike bottlenose or common dolphins. Pacific white-sided dolphins have a distinct color pattern: they are dark gray or black on their back, sides and belly but have a striking large gray or off-white patch on both sides.
Pacific white-sided dolphins are found in cold, temperate waters of the North Pacific Ocean from North America to Asia. They become most abundant in shallow, shelf waters off southern California from November to April and then off Oregon and Washington in May. This change in geographic distribution leads scientists to suspect the population is migrating seasonally from the south to the north in the eastern North Pacific.
Although not much is known, it is thought that female Pacific white-sided dolphins give birth every other year and gestation lasts about twelve months. Newborn calves are about 3 feet (0.9 m) in length. Calves nurse at least six months and most births occur from April to August.
Pacific white-sided dolphins are gregarious and often found in large groups of tens, hundreds and sometimes thousands. They are fast, acrobatic and playful and are one of the species commonly found bow-riding off boats. These dolphins are often seen with other cetaceans, including Northern right whale dolphins and Risso's dolphins.
Scientists do not have a good estimate for the entire population, but estimates for the eastern North Pacific range from 26,000 to 100,000 individuals.
At The Marine Mammal Center
Volunteers from The Marine Mammal Center rescued a 4-to-5 foot-long Pacific white-sided dolphin that had stranded at Rockaway Beach in Pacifica, California on February 16, 2011. Named "Pacifica" by her rescuers, the juvenile female cetacean is in good body condition with minor traumatic lesions. She is under 24-hour medical care at The Marine Mammal Center and will undergo diagnostic tests to determine her health and possibility of survival. Typically, stranded cetaceans do not survive even though The Marine Mammal Center gives them the best care possible.