White Sided Dolphin

 

Common Name: White-sided Dolphins

Class: Mammalia

Order: Cetacea

Family: Delphinidae

Genus: Lagenorhynchus

Species: Six species:

     Atlantic white-sided dolphin L. acutus

     White-beaked dolphin L. albirostris

     Peale's dolphin L. australis

     Hourglass dolphin L. cruciger

     Pacific white-sided dolphin L. obliquidens

     Dusky dolphin L. obscurus

Pacific white-sided dolphin Lagenorhynchus obliquidens

Taxonomy/Description

Pacific white-sided dolphins belong to the Mammalian Order Cetacea, in the suborder Odontoceti.  All toothed whales belong to the suborder Odontoceti, which is Latin for "toothed whales".  This dolphin belongs to the oceanic dolphin family, Delphinidae.  Other members of this family include the killer whale, long-beaked common dolphin, and pilot whale.  The Pacific white-sided dolphin's scientific name is Lagenorhynchus obliquidens.  The generic name, Lagenorhynchus means "flagon nosed", referring to the genus' stubby rostrum.

Pacific white-sided dolphin Lagenorhynchus obliquidens

Dolphin species of the genus Lagenorhynchus have tiny, less prominent rostrums.  They do not have a defined forehead like the commonly seen bottle-nosed dolphins of marine parks and aquaria.  The dorsal and pectoral fins are pointed.  Most species are colored dark gray dorsally, with lateral stripes of light gray and white.  White-sided dolphins range in size from 6-8ft in length and 300lbs in weight.

Atlantic white-sided dolphin Lagenorhynchus acutus

White-sided dolphins are commonly observed in large pods of over one hundred animals.  Occasionally pods of over a thousand are observed.  However, they usually form small groups of 6-15 individuals.  They are very fast swimmers, as well as acrobatic.  Acrobatics may be used as a form of communication, possibly to alert other dolphins of large food sources. Their diet consists mainly of squid and small fish species.  Fish species include herring, hake, sardines, and anchovies.  It is not uncommon to see this species bow riding on boats or large baleen whales.  Association with other marine mammals is also common.  Breeding occurs throughout the summer.  Gestation is estimated at 12 months.  Newborn calves are 3-4ft in length.  Calves are weaned at 1.5 years.

Peale's dolphin Lagenorhynchus australis

 

Atlantic white-sided dolphin Lagenorhynchus acutus

The specific name, acutus, is Latin for "pointed", referring to this species' short, evident beak.  Atlantic white-sided dolphins are native to the coastal temperate waters of the North Atlantic Ocean.  They are dark gray or black dorsally, striped lighter gray laterally, and light gray or white ventrally.  A white stripe within the lighter gray area extends from the middle torso to the tailstock.

Atlantic white-sided dolphin Lagenorhynchus acutus

 

White-beaked dolphin Lagenorhynchus albirostris

The specific name, albirostris, is derived from the Latin albus, meaning "white", and rostrum, meaning "snout".  This refers to the species' prominent white beak.  The white-beaked dolphin is predominantly dark gray with a whitish "saddle patch" across its back and torso, eventually extending onto its tailstock.  The white snout is very evident as well.  White-beaked dolphins inhabit the temperate and sub-arctic waters of the North Atlantic Ocean.

Peale's dolphin Lagenorhynchus australis

The specific name, australis, is Latin for "southern".  This refers to the range of the species, which is primarily the temperate waters off the coast of South America.  Peale's dolphin is black or dark gray dorsally, with lateral lighter gray striping on the tailstock and torso, with a white underside.

Peale's dolphin Lagenorhynchus australis

 

Hourglass dolphin Lagenorhynchus cruciger

The specific name, cruciger, is derived from the Latin crucis, meaning "cross", and gero, meaning "to bear".  This may refer to the distinctive hourglass pattern present on the torso.  Hourglass dolphins are black or dark gray with white undersides and a very distinctive white striping pattern resembling an hourglass.  The striping begins near the dolphin's eye, then tapers just below the dorsal fin, and continues down along the remainder of the body as it widens once again.  Hourglass dolphins prefer the cool temperate and Antarctic waters of the Southern Hemisphere.

Pacific white-sided dolphin Lagenorhynchus obliquidens

The specific name, obliquidens,The Pacific white-sided dolphin lives in temperate waters of the Pacific Ocean.  This range includes the northern coast of the United States and Canada, and the coast of Japan.  These animals prefer deep waters, and are often observed in the open ocean, far from the shallow shoreline waters.  More inshore sightings have recently been recorded.

Pacific white-sided dolphin Lagenorhynchus obliquidens

 

Dusky dolphin Lagenorhynchus obscurus

The specific name, obscurus, is Latin for "dark or indistinct".  This may refer to this species' coloration.  Dusky dolphins are dark gray or black dorsally, including their beak, with a lighter gray and white torso and pectoral fins.  Lighter stripes also mark their tailstock.  The dusky dolphin is native to the offshore temperate waters of the Southern Hemisphere.

Dusky dolphin Lagenorhynchus obscurus

Conservation

These species are not listed as endangered, nor are most threatened by commercial hunting.  Fishing nets may accidentally drown thousands each year, but this has little effect on the species' overall survival.  The estimate for the total Pacific white-sided dolphin population is 931,000 individuals.  The worldwide population of hourglass dolphins is estimated at 144,000.  Estimates for other species range in the tens of thousands, and none are thought to face immediate danger of extinction.\

Atlantic white-sided dolphin Lagenorhynchus acutus

Peale's dolphin Lagenorhynchus australis

Content provided by Canisius College students under the direction of Michael Noonan, PhD.