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Lissodelphis borealisnorthern right whale dolphin

By Deborah Ciszek

Geographic Range

These cetaceans are found only in the northern Pacific Ocean, between the latitudes 35 degrees North and 51 degrees North.

Habitat

These animals live in deep continental shelf and offshore waters where the temperatures vary between 8 and 24 degrees C. They approach shore only where very deep water can be found near the coast.

Physical Description

Northern right whale dolphins have an unusually slender body shape, and they do not have a dorsal fin or ridge. They have small, curved flippers, and small flukes. They are mostly black, but they have a well defined white band on their belly. Males and females have the same body shape and color pattern, the only sexually dimorphism being that males can attain greater length (up to 3 meters) and weight than females.

  • Range mass
    90 to 113 kg
    198.24 to 248.90 lb

Reproduction

Virtually nothing is known about reproduction or mating in this species.

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

Behavior

Northern right whale dolphins usually travel in large groups of up to 2,000 individuals. Average herd size is about 200. Groups sometimes swim in various geometric configurations, such as a V-shape. These dolphins can swim quickly, over 40 km/hr. They can swim near the surface without greatly disturbing the water surface, probably because they do not have a dorsal fin. They are known to occasionally perform fluke slaps and breaches. The maximum dive time that has been recorded for them is 6.25 minutes. They often travel with other species of marine mammals, most commonly the Pacific white-sided dolphin. Click and whistle vocalizations have been reported in northern right whale dolphins, but these have not yet been studied.

Communication and Perception

Food Habits

Northern right whale dolphins feed mainly on squid and lanternfish, but they also eat other kinds of fish.

  • Animal Foods
  • fish
  • mollusks

Economic Importance for Humans

Economic Importance for Humans: Positive

The blubber from these animals is used to make oil.

Conservation Status

The North Pacific squid driftnet fishery operated out of Japan, Korea, and Taiwan targets northern right whale dolphins. It is estimated that between 1985 and 1990 this fishery took 15,000 to 20,000 dolphins per year. The population has been depleted to anywhere from 24 to 73 percent of its pre-exploitation size. A moratorium on high seas driftnets could allow population levels to increase to previous levels. This species is listed on CITES Appendix II.

Contributors

Deborah Ciszek (author), University of Michigan-Ann Arbor.

Glossary

Pacific Ocean

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.

World Map

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

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.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

References

Jefferson, T.A. and M.W. Newcomer. 1993. Lissodelphis borealis. Mammalian Species No. 425, The American Society of Mammalogists.

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