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Mesoplodon bidensSowerby's beaked whale

By Rachel Mortensen

Geographic Range

Sowerby's beaked whales are found in temperate to sub arctic waters in the eastern and western North Atlantic. They are found around the British Isles and are known to occur from Newfoundland to Massachusetts. Sowerby's beaked whales occur as far north as Labrador in the west and in the Norwegian Sea in the east, southern limit is thought to be somewhere between 33ºN and 41ºN. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006a; ; Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003; Ruff and Wilson, 1999; "MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006a; Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003; Ruff and Wilson, 1999)

Habitat

Sowerby's beaked whales are found in cool to warm temperate offshore waters of the North Atlantic Ocean. They are usually observed in open water and most often seen in areas were depths range from 198 to 1524 m. (Carwardine, 2002; Clapham, et al., 2002; Mottet, 2003)

  • Range depth
    198 to 1524 m
    649.61 to 5000.00 ft

Physical Description

Mesoplodon bidens is bluish grey to slate grey in color, with a lighter underside, grey and white spots may be present on the body with limited scaring. Mesoplodon bidens have a long slender beak that contains a pair of teeth midway up the lower jaw. They have a long think body, long flippers for the Mesoplodon family, and no notch in the fluke. The dorsal fin is quite small with a rounded tip and may appear falcate. Young M. bidens have a light blusih grey to white underside, more prominant than in adults. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006b; ; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003)

  • Sexual Dimorphism
  • male larger
  • Range mass
    1000 to 1300 kg
    2202.64 to 2863.44 lb
  • Range length
    5 to 5.5 m
    16.40 to 18.04 ft

Reproduction

Nothing is known about the mating systems of M. bidens. (Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002)

Little in known about general reproductive behavior of M. bidens. Mating is thought to occur in late winter, with births late in spring and gestation lasting about 12 months. Young are about 2.4 to 2.7 meters in length and weigh about 185 kg. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006b; Barrett and Macdonald, 1993)

  • Breeding interval
    Breeding interval is not known for Sowerby's beaked whales.
  • Breeding season
    Mating is thought to occur in late winter.
  • Average number of offspring
    1
  • Average gestation period
    12 months

Sowerby's beaked whale females provide milk for their young and protect them. There is no other available information on parental investment. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006b; Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003; Ruff and Wilson, 1999)

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

Lifespan/Longevity

The is no data on the lifespan in M. bidens. ("MarineBio.org", 2006; Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002)

Behavior

When surfacing, Sowerby's beaked whales have been observed coming up at a steep angle with the head breaking the surface first. They then take a series of quick breaths (about 4 to 6) over a period of a minute. After a minute at the surface they take a longer dive for about ten to fifteen minutes, and may resurface up to 800 meters away. They have been recorded to dive up to 28 minutes. The blows of M. bidens are usually invisible or fairly inconspicuous. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006b; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003)

Sowerby's beaked whales are social animals, most often observed in pairs. Occasionally they are seen in pods ranging from 3 to 10 individuals. Sowerby's beaked whales stay clear of boats, so sightings are rare and most observations of these whales are from strandings. Sowerby's beaked whales often strand in pairs; sometimes as many as six individuals will stand together. They are the most commonly stranded species in the genus Mesoplodon. There are records of M. bidens strandings year round, except for the month of February. The highest density of strandings appears to occur between the months of July and September. (Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003)

Home Range

There is no information on the home range of M. bidens.

Communication and Perception

A young animal, that was kept in a dolphinarium for a few hours, was recorded using high frequency sound pulses to echolocate. (Barrett and Macdonald, 1993)

Food Habits

The diet of Sowerby's beaked whales consists mostly of squid, octopus, and fish. A necropsy of one individual showed stomach contents that included bottom-dwelling and deep water fish. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006b; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003)

  • Animal Foods
  • fish
  • mollusks

Predation

There is no information about predation on Sowerby's beaked whales. Once they reach their adult size it is likely that they are protected from much predation. Killer whales and large sharks may target Sowerby's beaked whales. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006a; Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002; Culik, 2003; Mottet, 2003; Ruff and Wilson, 1999)

Ecosystem Roles

Little is known about the role of Sowerby's beaked whales in the northern Atlantic ecosystem. They are undoubtedly predators of marine organisms. ("MarineBio.org", 2006; Carwardine, 2002; Clapham, et al., 2002)

Economic Importance for Humans: Positive

Sowerby's beaked whales were once infrequently harvested by Norwegian whalers. They are no longer hunted actively. (Clapham, et al., 2002)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Sowerby's beaked whales are occasionally caught in fishing gear, damaging nets in the process. Arguably this is more traumatic for the whales than fishing crews. (Clapham, et al., 2002; Culik, 2003)

Conservation Status

There is very little data on Sowerby's beaked whales. As a result there is little information on population sizes, current or historic, to determine conservation status. This species is rarely seen in the open ocean, most records are from strandings. ("MarineBio.org", 2006; Barrett and Macdonald, 1993; Carwardine, 2002; Clapham, et al., 2002; Ruff and Wilson, 1999)

Other Comments

As with all beaked whales (Ziphiidae) there is very little data on M. bidens. This species was the first of the beaked whales to be described. It was described by John Sowerby in 1804. ("MarineBio.org", 2006; "Whale and Dolphin Conservation Society", 2006b; Carwardine, 2002; Clapham, et al., 2002)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Rachel Mortensen (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

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.
echolocation

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.

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.

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).

piscivore

an animal that mainly eats fish

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

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).

visual

uses sight to communicate

viviparous

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

young precocial

young are relatively well-developed when born

References

2006. "MarineBio.org" (On-line). Mesoplodon bidens. Accessed October 22, 2006 at http://marinebio.org/species.asp?id=334.

2006. "Whale and Dolphin Conservation Society" (On-line). Accessed October 22, 2006 at http://www.wdcs.org/dan/publishing.nsf/allweb/BBA6AFE5C70302F7802569CF00406D58.

2006. "Whale and Dolphin Conservation Society" (On-line). Sowerby's Beaked Whale Distribution and Threats. Accessed October 22, 2006 at http://www.wdcs.org/dan/publishing.nsf/allweb/342DF2CCB12D2FD0802569CF00404FB9.

Barrett, P., D. Macdonald. 1993. Princeton Field Guides: Mammals of Europe. Princeton New Jersey: Princeton University Press.

Carwardine, M. 2002. Whales Dolphins and Porposies. New York City, New York: Dorling Kindersley.

Clapham, P., J. Powell, R. Reeves, B. Stewart. 2002. National Audubon Society Guide to Marine Mammals. New York: Alfred A. Knopf.

Culik, B. 2003. "Convention on Migratory Species" (On-line). Accessed October 22, 2006 at http://www.cms.int/reports/small_cetaceans/data/m_bidens/m_bidens.htm.

Mottet, C. 2003. "Texas Marine Mammal Standing Network" (On-line). Accessed October 22, 2006 at http://www.sci.tamucc.edu/tmmsn/29Species/sowerbysbeakedwhale.html.

Ruff, S., D. Wilson. 1999. The Smithsonian Book of North American Mammals. Washington D.C.: Smithsonian Institution Press.

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