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Mesoplodon stejnegeriStejneger's beaked whale

By Rebecca Ann Csomos

Geographic Range

Mesoplodon stejnegeri ranges from the Bering Sea to California and Japan, inhabiting only the cool temperate waters of the Northern Pacific Ocean. (Nowak, 1999)

Habitat

Stejneger's beaked whales, Mesoplodon stejnegeri, inhabit the deep waters of the ocean far from the shorelines. These animals are rarely seen at sea. They prefer a habitat with cool water. Mesoplodon stejnegeri has been observed living sympatrically with Hubb's beaked whales where the ranges of the two species overlap off the coast of northern Japan to Oregon and British Columbia. (Loughlin and Perez, 13 December 1985)

Physical Description

Mesoplodon stejnegeri ranges in length from 3 to 7 m, although they are generally longer than 5.3 m. Females are normally longer than males, and the crania of females are larger than those of males.

Both sexes are uniformly gray to black, with light pale countershading ventrally, although males tend to be more uniformly dark.

Mesoplodon stejnegeri is distinguished from other Mesoplodons by tooth shape and position. Members of this species have two large, exposed, tusk-like teeth on the lower jaw (Nowak 1999). These teeth are also distinctively larger in males.

Scarring, which is present on most M. stejnegeri, results from intraspecific fighting over mates, and is inflicted by the teeth while the mouth is closed (Ridgway and Harrison 1989). (Nowak, 1999; Ridgway and Harrison, 1989)

  • Sexual Dimorphism
  • female larger
  • male more colorful
  • ornamentation
  • Range length
    3 to 7 m
    9.84 to 22.97 ft

Reproduction

Nothing is known about the reproduction of M. stejnegeri, although it is speculated that litter size is one and parturition occurs in the spring and summer. (Loughlin and Perez, 13 December 1985)

  • Range number of offspring
    1 (low)
  • Average number of offspring
    1

Although parental investment in this species has not been documented, because these animals are mammals we can infer that females provide a great deal of parental care. They are likely to provide their young with protection as well as food, in the form of milk, until the calves are able to care for themselves.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Behavior

These beaked whales are deep divers. They swim at 3 to 4 knots on average, with maximum speeds reaching 6 knots. This species usually swims in pods containing 2 to 6 individuals, although groups of 5 to 15 individuals have been observed. Within these social pods, individual whales vary in size, sex, and age. They swim abreast in the pods, touching one another, and they surface and submerge simultaneously. A common pattern of several shallow dives followed by a longer dive of about 10 to 15 minutes has been noted. Also while in these pods, members of this species take 2 to 3 low blows in unison, which are proceeded by sounds described as "roars, lowing and sobbing groans." (Loughlin and Perez, 13 December 1985)

Communication and Perception

Food Habits

Mesoplodon stejnegeri feeds primarily on deep-water squid. The diet includes both cephalopods and fish. A school of salmon was observed being chased by M. stejnegeri off the coast of Japan, and this species is sometimes trapped in salmon driftnets. (Loughlin and Perez, 13 December 1985)

  • Animal Foods
  • fish
  • mollusks

Economic Importance for Humans: Positive

The meat of M. stejnegeri is considered palatable when cooked, but the Makah Indians of Washington reported cases of diarrhea after eating the blubber and flesh. Commercial fisheries, primarily in Japan, take a small number of M. stejnegeri yearly. (Loughlin and Perez, 13 December 1985)

  • Positive Impacts
  • food

Conservation Status

These whales are a conservation concern. They are listed as Appendix II by CITES, and Data deficient by IUCN.

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Rebecca Ann Csomos (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, 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

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

diurnal
  1. active during the day, 2. lasting for one day.
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.

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

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.

nomadic

generally wanders from place to place, usually within a well-defined range.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

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

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

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).

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Jefferson, T., S. Leatherwood, M. Webber. 1993. Marine Mammals of the World. Rome: United Nations Environment Programme.

Loughlin, T., M. Perez. 13 December 1985. Mesoplodon stejnegeri. Mammalian Species, No. 250: pp. 1-6.

Nowak, R. 1999. Walker's Mammals of the World, 6th Edition. Baltimore and London: The Johns Hopkins University Press.

Ridgway, S., S. Harrison. 1989. Handbook of Marine Mammals, Volume 4: River Dolphins and the Larger Toothed Whales. New York: Academic Press.

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