Animal Diversity Web

Ge­o­graphic Range

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)

• Biogeographic Regions
• pacific ocean
  • native

Habi­tat

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)

• Habitat Regions
• temperate
• saltwater or marine

• Aquatic Biomes
• pelagic
• coastal

• Range depth

  0 to 1000 m

  0.00 to 3280.84 ft

Phys­i­cal De­scrip­tion

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)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger

• Range mass

  78 to 200 kg

  171.81 to 440.53 lb

• Range length

  1.7 to 2.5 m

  5.58 to 8.20 ft

• Average length

  2.0 m

  6.56 ft

Re­pro­duc­tion

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)

• Key Reproductive Features
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

• Breeding interval

  Pacific white-sided dolphins breed once yearly

• Breeding season

  August-October

• Range number of offspring

  1 (high)

• Average number of offspring

  1

• Average number of offspring

  1

  AnAge

• Range gestation period

  9 to 12 months

• Range weaning age

  18 (high) months

• Average weaning age

  12 months

• Range time to independence

  18 (high) months

• Range age at sexual or reproductive maturity (female)

  8 to 11 years

• Range age at sexual or reproductive maturity (male)

  10 to 11 years

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)

• Parental Investment
• precocial
• female parental care
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifes­pan/Longevity

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)

• Range lifespan
  Status: captivity

  46 (high) years

• Typical lifespan
  Status: captivity

  36 (high) years

Be­hav­ior

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)

• Key Behaviors
• natatorial
• motile
• nomadic
• social
• colonial

Home Range

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.

Com­mu­ni­ca­tion and Per­cep­tion

Lagenorhynchus obliq­uidens 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. ("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)

• Communication Channels
• visual
• tactile
• acoustic

• Perception Channels
• tactile
• acoustic
• echolocation
• chemical

Food Habits

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.

Lagenorhynchus obliq­uidens 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. ("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)

• Primary Diet
• carnivore
  • piscivore
  • molluscivore

• Animal Foods
• fish
• mollusks

Pre­da­tion

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 Lagenorhynchus obliq­uidens. 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)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • humans (Homo sapiens)
  • killer whales (Orchinus orca)

Ecosys­tem Roles

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)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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)

• Positive Impacts
• food
• ecotourism
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Pa­cific white-sided dol­phins neg­a­tively af­fect com­mer­cial fish­eries. They com­pete with the fish­eries for fish and often be­come tan­gled in drift­nets. (Nowak, 2003; Stew­art, et al., 2002)

Con­ser­va­tion Sta­tus

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.” Lagenorhynchus obliq­uidens has no spe­cial sta­tus ac­cord­ing to the US Fed­eral List and the State of Michi­gan list. (Ham­mond, et al., 2012; Hobbs and Jones, 1993)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  Appendix II

• State of Michigan List

  No special status

Con­trib­u­tors

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.

Ref­er­ences

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