Pacific white-sided dolphins, Lagenorhynchus obliqiudens, can be found throughout the temperate waters of the northern Pacific Ocean. This pelagic species is endemic to the cold regions of the Pacific, most commonly occurring between the latitudes of 38 degrees N and 47 degrees N. The species in not found in arctic and tropical waters.
They also range in the western Pacific Ocean from the South Bering Sea to southern Japan.
White-sided dolphins are found along the west coast of North America, and migrate seasonally in north-south (latitudinal) directions. These dolphins are most abundant in shelf waters off southern California during the winter and off Oregon and Washington during late spring. Historically, Pacific white-sided dolphins have been observed as far south as the Gulf of California. In recent years, Lagenorhynchus obliqiudens has declined in the Gulf of California as water temperatures have increased. (Salvadeo, et al., 2010; Stewart, et al., 2002)
Pacific white-sided dolphins are common in temperate seas. They are most abundant in deeper waters in the open ocean and can dive as deep as 1000 m. Pacific white-sided dolphins exploit a large habitat including open ocean and near-shore waters. ("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Black, 1994; Brown and Norris, 1956; Rechsteiner, et al., 2013; Ridgway and Harrison, 1998; Salvadeo, et al., 2010)
Pacific white-sided dolphins have a complex color pattern. They are black or dark gray with distinct light gray stripes on their sides, dorsal fin, and flippers. The stripes on their sides begin on the side of the face ahead of the eye and extend to the base of the tail. A large patch of light gray dominates the anterior of the dorsal fin. Their eyes and mouth have dark coloration. Distinguishing features of Pacific white-sided dolphins are their tall, hooked, bicolored dorsal fins, located at the center of their back. Pacific white-sided dolphins have pectoral fins that share the same coloration and are rounded.
White-sided dolphins are 1.7-2.5 m long, with an average of 2.0 m. Males can reach this length of 2.5 m while females can reach just 2.3 m. Adult white-sided dolphins typically weigh about 135-180 kg but males can weigh up to 200 kg. Newborn Pacific white-sided dolphins are 0.9-1.05 m long and weigh approximately 15 kg.
The bodies of Pacific white-side dolphins are robust, and torpedo-shaped. Pacific white-sided dolphins have 21 to 33 pairs of slightly-pointed teeth per jaw. Pacific white-sided dolphins have short beaks. Their skulls have an average length of 39 cm. ("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Brown and Norris, 1956; Marino, 1999; Nowak, 2003; Prevost, 1996; Rechsteiner, et al., 2013; Ridgway and Harrison, 1998; Stewart, et al., 2002)
Pacific white-sided dolphins breed seasonally from August to October. Although very little is known about their mating system, Connor (1994) suggests it is unlikely they are monogamous. (Black, 1994; Connor, 1994; Ferrero and Walker, 1996; Stewart, et al., 2002)
The gestation period of Pacific white-sided dolphins lasts for 9-12 months. Most calving occurs during late spring and summer, and just one offspring is born. Pacific white-sided dolphins are 0.9 m-1.5 m in length at birth. Calves weigh, on average, 15 kg (range 13-22 kg) when born, and nurse for up to 18 months after birth. Pacific white-sided dolphins give birth at a minimum of once every two years.
Female Pacific white-sided dolphins reach sexual maturity around a length of 1.7 m and between the ages of 8 and 10 years. Males reach sexual maturity at lengths around 1.7-1.8 m between the ages of 10 and 11 years. Like other mammals, fertilization occurs internally. Pacific white-sided dolphins give birth to relatively well-developed young. (Black, 1994; Ferrero and Walker, 1996; Mann, 2000; Nowak, 2003; Rechsteiner, et al., 2013; Salvadeo, et al., 2010; Stewart, et al., 2002)
A Pacific white-sided dolphin calf stays with its mother until it reach independence around 18 months. Males are not involved in parental care beyond the mating process. (Ferrero and Walker, 1996; Mann, 2000)
Weigl (2005) estimates Pacific white-sided dolphins can live up to 46 years in captivity. Wilson and Ruff (1999) reported a captive Pacific white-sided dolphin lived to be 36 years. It is unknown how long they can live in the wild. (Weigl, 2005; Wilson and Ruff, 1999)
Pacific white-sided dolphins are mobile creatures specialized for swimming. They can be found in groups ranging from just a few individuals to 100 individuals. These groups are sometimes separated into smaller subgroups or pods, which average about 15 members (typically 10 to 25). Pods consist of all ages and both sexes.
Pacific white-sided dolphins are social animals. They are often found in mixed-species aggregations with other cetaceans, pinnipeds, and sea birds. They associate most often with northern right whale dolphins (Lissodelphis borealis) and Risso’s dolphins (Grampus griseus).
Pacific white-sided dolphins are active at the water’s surface. They are known to ride the bow waves of ships. Pacific white-sided dolphins are also well known for their aerial displays. They leap clear of the water, and are the only dolphins of the eastern Pacific known to turn complete somersaults under natural conditions. (Black, 1994; Dahlheim, et al., 2009; Nowak, 2003; Ridgway and Harrison, 1998; Stewart, et al., 2002)
Generally, most pelagic mammals will not defend or use a home range. No home range has been reported and it's assumed Pacific white-sided dolphins do not have one.
("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Baird, 1998; Black, 1994; Henderson, 2010; Ridgway and Harrison, 1998; Yeater, et al., 2014)uses echolocation clicks that range primarily from 20 to over 100 kHz. A study performed on captive Pacific white-sided dolphins revealed they use echolocation clicks and touch to interpret their surroundings. Pacific white-sided dolphins also produce whistle vocalizations, similar to other dolphins, in order to communicate with one another. They communicate visually, acoustically, and through touch. According to Henderson (2010) Pacific white-sided dolphin vocalizations differ across behavioral states.
Pacific white-sided dolphins are versatile and opportunistic feeders. Their carnivorous diet consists of small fish found in large schools and squid (Loligo). They typically consume Pacific herring (Clupea pallasii), capelin (Mallotus villosus), market squid (Loligo opalescens), Pacific sardines (Sardinops sagax) and mackerel (Scomber japonicus) when available. An average-sized Pacific white-sided dolphin needs to consume around 12.5-15.8 kg of fish per day or approximately 16-20% of its body mass daily.
("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Black, 1994; Brown and Norris, 1956; Dailey, et al., 1993; Rechsteiner, et al., 2013; Ridgway and Harrison, 1998; Stewart, et al., 2002)has been observed feeding in groups averaging in size from 11-50 individuals. They forage while simultaneously milling. They are not considered deep divers and typically feed close to the shelf in shallow depths.
Due to their harmful effects on fisheries, humans (Homo sapiens) kill Pacific white-sided dolphins. In regions of Japan, they are hunted for their meat. Killer whales (Orchinus orca) are also known predators of . Both humans and killer whales are predators of adult and young Pacific white-sided dolphins.
The coloration of Pacific white-sided dolphins allows them to be camouflaged. By having a light colored underside and a dark colored back, Pacific white-sided dolphins can blend in with their surroundings when being viewed by a predator from both above and below. (Black, 1994; Nowak, 2003; Stewart, et al., 2002)
Pacific white-sided dolphins have a vital ecosystem role as consumers of fish. Seabirds often follow Pacific white-sided dolphins and consume fish the dolphins do not eat.
They are hosts for internal parasites including: nematodes (Anisakis simplex and Crassicauda), trematodes (Nasitrema globicephalae), and cestodes (Phyllobothrium delphini, Monorygma grimaldii, and Strobilocephalus triangularus). They are also hosts for external parasites called cirripedes (Xenobalanus). (Dailey and Walker, 1978; Martin, et al., 1970; Nowak, 2003; Stewart, et al., 2002)
Pacific white-sided dolphins are hunted for their meat by Japanese fishermen. They are important in the entertainment and tourism industry. For example, these dolphins are trained in marine mammal parks to perform tricks and are used to educate attendees about dolphins. It is also common for Pacific white-sided dolphins to be spotted during whale-watching expeditions. (Nowak, 2003; Stewart, et al., 2002)
The greatest threat to Pacific white-sided dolphins is high-seas driftnets used by commercial fisheries. The United Nations’ prohibition of high-seas driftnet fishing is the most significant attempt to conserve Pacific white-sided dolphins internationally. The United States requires fisheries in the Pacific to have acoustic warning signals to help prevent dolphins from being caught in driftnets. Although these signals have decreased the number of dolphins killed by driftnets, an average of 5.9 Pacific white-sided dolphins are caught and killed annually. Still, this is an improvement from historical deaths; Hobbs and Jones (1993) reported approximately 100,000 Pacific white-sided dolphins were killed between 1970 and 1990 by high-seas driftnet.
Pacific white-sided dolphins are harpooned in areas of Japan for human consumption. Although specific numbers are unknown, it is likely impact on Pacific white-sided dolphins due to Japanese harpooning is nominal.
Pacific white-sided dolphins are an Appendix II species, according to CITES. Per this Appendix, permits are required to trade Pacific white-sided dolphins internationally. Permits are only granted if the trade will not be detrimental to the survival of the species. Pacific white-sided dolphins are not threatened, but if current trade policies remain they could become endangered. The IUCN Red List lists Pacific white-sided dolphins as a species of “least concern.” (Hammond, et al., 2012; Hobbs and Jones, 1993)has no special status according to the US Federal List and the State of Michigan list.
Taylor Layton (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
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.
uses sound to communicate
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.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
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.
parental care is carried out by females
A substance that provides both nutrients and energy to a living thing.
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
mainly lives in oceans, seas, or other bodies of salt water.
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
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
National Oceanic and Atmospheric Administration. Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters. 86137. Seattle, Washington: NOAA, NMFS. 1980.
Baird, R. 1998. An interaction between Pacific white-sided dolphins and a neonatal harbor porpoise. Mammalia, 62/1: 129-133.
Black, N. 1994. Behavior and Ecology of Pacific White-Sided Dolphins (Lagenorhynchus obliquidens) in Monterey Bay, California (Thesis). San Francisco, California: San Francisco State University.
Brown, D., K. Norris. 1956. Observations of captive and wild cetaceans. Journal of Mammalogy, 37/3: 311-326.
Connor, R. 1994. The Lives of Whales and Dolphins. New York: Henry Holt and Company.
Dahlheim, M., P. White, J. Waite, G. Eckert. 2009. Cetaceans of southeast Alaska: Distributional and seasonal occurrence. Journal of Biogeography, 36/3: 410-426.
Dailey, M., D. Reish, J. Anderson. 1993. Ecology of the Southern California Blight: A Synthesis and Interpretation. Oakland, CA: University of California Press.
Dailey, M., W. Walker. 1978. Parasitism as a factor (?) in single strandings of southern California cetaceans. The Journal of Parasitology, 64/4: 593-596.
Ferrero, R., W. Walker. 1996. Age, growth, and reproductive patterns of the Pacific white-sided dolphin (Lagenorhynchus obliquidens) taken in high seas drift nets in the central North Pacific Ocean. Canadian Journal of Zoology, 74/9: 1673-1687.
Gibbons, E., B. Durrant, J. Demarest. 1995. Conservation of Endangered Species in Captivity: An Interdisciplinary Approach. New York: SUNY Press.
Hammond, P., G. Bearzi, A. Bjørge, K. Forney, L. Karkzmarski, T. Kasuya, W. Perrin, M. Scott, J. Wang, R. Wells, B. Wilson. 2012. "Lagenorhynchus obliquidens" (On-line). The IUCN Red List of Threatened Species. Accessed March 27, 2015 at http://www.iucnredlist.org/details/11145/0.
Hayssen, V., A. Tienhoven. 1993. Asdell's Patterns of Mammalian Reproduction: A Compendium of Species-specific Data. New York: Cornell University Press.
Henderson, E. 2010. Cetaceans in the Southern California Bight: Behavioral, Acoustic, and Spatio-temporal Modeling (Thesis). San Diego, CA: University of California.
Hobbs, R., L. Jones. 1993. Impacts of high seas driftnet fisheries on marine mammal populations in the North Pacific. International North Pacific Fisheries Commission Bulletin, 53/3: 409-434.
Mann, J. 2000. Cetacean Societies: Field Studies of Dolphins and Whales. Chicago, Illinois: University of Chicago Press.
Marino, L. 1999. Brain growth in the harbor porpoise and Pacific white-sided dolphin. Journal of Mammalogy, 80/4: 1353-1360.
Martin, W., C. Haun, H. Barrows, H. Cravioto. 1970. Nematode damage to brain of striped dolphin, Lagenorhynchus obliquidens. Transactions of the American Microscopical Society, 89/2: 200-205.
Nowak, R. 2003. Walker's Marine Mammals of the World. Maryland: The Johns Hopkins University Press.
Prevost, J. 1996. White-Sided Dolphins. Minnesota: ABDO Publishing Company.
Rechsteiner, E., D. Rosen, A. Trites. 2013. Energy requirements of Pacific white-sided dolphins (Lagenorhynchus obliquidens) as predicted by a bioenergetic model. Journal of Mammalogy, 94/4: 820-832.
Ridgway, S., R. Harrison. 1998. Handbook of Marine Mammals: The Second Book of Dolphins and the Porpoises. Amsterdam, the Netherlands: Elsevier BV.
Salvadeo, C., D. Lluch-Belda, A. Gomez-Gallardo, J. Urban-Ramirez, C. MacLeod. 2010. Climate change and a poleward shift in the distribution of the Pacific white-sided dolphin in the northeastern Pacific. Endangered Species Research, 11/1: 13-19.
Stewart, B., P. Clapham, J. Powell, R. Reeves. 2002. Guide to Marine Mammals of the World. New York: Knopf Doubleday Publishing.
Weigl, R. 2005. Longevity of Mammals in Captivity: from the Living Collections of the World: A List of Mammalian Longevity in Captivity. Stuttgart, Germany: E. Schweizerbart'sche.
Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Canada: UBC Press.
Yeater, D., H. Hill, N. Baus, H. Farnell, S. Kuczaj. 2014. Visual laterality in belugas (Delphinapterus leucas) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) when viewing familiar and unfamiliar humans. Animal Cognition, 17/6: 1245-1259.