Sowerby’s beaked whale (Mesoplodon bidens)

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Sowerby’s beaked whale fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Sowerby’s beaked whale description

Sowerby’s beaked whale is one of the more frequently sighted beaked whales in the North Atlantic Ocean, but like the rest of the Ziphiidae family very little is known about it ⁽⁴⁾. While most beaked whale species are extremely hard to differentiate from one another, Sowerby’s beaked whale can be recognised by its very long snout, or ‘beak’, which is proportionately the longest of all beaked whales in its range ^{(3) (4)}. This species also has a bulge on its forehead ⁽³⁾.

Like other beaked whales, Sowerby’s beaked whale has a torpedo-shaped body and relatively small flippers. It has a small, triangular dorsal fin, which is located about two-thirds of the way along its back ⁽⁴⁾, and its tail fin is unnotched ^{(2) (3)}. This species has a habit of raising its long beak at a steep angle as it surfaces from the water ⁽⁴⁾.

As in other beaked whales, two teeth are visible in the middle of the lower jaw of the male Sowerby’s beaked whale ^{(3) (4)}. It is presumed that these teeth are used in competition between males, an idea backed up by the significant scarring which can be seen on the flanks of adult males ^{(2) (3)}. Only male beaked whales possess these teeth, and they are the only teeth in the mouth ⁽⁴⁾.

Little is known about the colouration of Sowerby’s beaked whale, but it generally appears to be charcoal grey, with a lighter belly and often with lighter spots on the body. These spots are less common in juveniles ⁽³⁾. Male Sowerby’s beaked whales are thought to be slightly larger than the females ⁽³⁾, while juveniles have a relatively shorter beak than the adults ⁽⁴⁾.

Also known as

North Atlantic beaked whale, North Sea beaked whale.

French

Mésoplodon De Sowerby.

Spanish

Ballena De Pico De Sowerby, Zifio De Sowerby.

Size

Adult length: up to 5.5 m ^{(2) (3)}

Newborn calf length: 2.4 - 2.7 m ⁽²⁾

Adult weight: 1,000 - 1,300 kg ⁽⁴⁾

Newborn calf weight: 185 kg ⁽²⁾

Sowerby’s beaked whale biology

Sowerby’s beaked whale, like other beaked whales, is extremely hard to observe due to its deep offshore habitat, its long dive times, similarities in appearance with other beaked whales, and its inconspicuous blows at the surface ⁽⁸⁾. As a consequence, little is known about the social structure of Sowerby’s beaked whale, although it has been observed in groups of three to ten ^{(4) (8)}, with groups consisting of both males and females ⁽⁴⁾.

Knowledge of the diet of Sowerby’s beaked whale is limited, but studies have suggested that it may consist primarily of deep sea fish, including Atlantic cod (Gadus morhua), as well as squid ^{(1) (9)}. To reach the habitat of its prey, Sowerby’s beaked whale must make deep dives, and its dive time has been observed to be between 12 and 28 minutes long ^{(4) (8)}. Like other beaked whales, Sowerby’s beaked whale has a pair of external grooves on the throat which allow the mouth floor to be distended, creating a vacuum that sucks prey into the mouth. The prey is then swallowed whole ⁽²⁾.

As in other beaked whales, competition between males over mating rights is probably common, and male Sowerby’s beaked whales may use their teeth, or tusks, in confrontations. This would help explain observations of significant scarring down their bodies ⁽¹⁰⁾.

The breeding season of Sowerby’s beaked whale is thought to be late winter to spring ⁽³⁾. Like all cetaceans, Sowerby’s beaked whale gives birth to a single calf at a time, and this species is believed to have a 12-month gestation period ⁽²⁾.

Sowerby’s beaked whale range

Sowerby’s beaked whale occurs primarily in the cold, deep waters of the North Atlantic Ocean. In the west of its range, it has been sighted from Labrador and Newfoundland in Canada to Massachusetts in the United States, while in the east it occurs around the polar waters of Arctic Norway and the North Sea ^{(1) (3) (6) (7)}.

There have also been sightings, primarily strandings, of Sowerby’s beaked whale outside of its normal range, as far south as Madeira in the east, the Azores in the central Atlantic, and the Florida coast in the west ⁽⁷⁾.

Sowerby’s beaked whale habitat

Like the majority of beaked whale species, Sowerby’s beaked whale prefers deeper waters where most of its prey can be found. Sightings of this species have occurred primarily in waters between 550 and 1,500 metres in depth ^{(1) (8)}.

Sowerby’s beaked whale status

Sowerby’s beaked whale is classified as Data Deficient (DD) on the IUCN Red List ⁽¹⁾ and is listed on Appendix II of CITES ⁽⁵⁾.

Sowerby’s beaked whale threats

Information regarding the abundance and health of the Sowerby’s beaked whale population is rather limited. This species is, however, not believed to be too uncommon, although it is potentially vulnerable to low-level threats ⁽¹⁾.

Sowerby’s beaked whale was an observed bycatch of a small-scale fishery that used large drift nets along the Georges Bank, off the north-eastern coast of North America, but this fishery has now closed ^{(1) (7)}. This species has also occasionally been caught by whalers in Newfoundland, Iceland and the Barents Sea ⁽¹⁾.

Like other beaked whales, Sowerby’s beaked whale is believed to be at risk from man-made sounds, such as those created by large ocean-going ships, sonar and seismic exploration ⁽¹¹⁾. In addition, it may potentially be vulnerable to swallowing discarded plastic ⁽¹⁾.

The projected impacts of climate change are likely to have an effect on the environment on which Sowerby’s beaked whale depends, but the exact impacts this will have are currently unknown ⁽¹²⁾.

Sowerby’s beaked whale conservation

Sowerby’s beaked whale is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any international trade in this whale should be carefully controlled ⁽⁵⁾.

There are no other specific conservation measures currently known to be in place for Sowerby’s beaked whale. However, research has been recommended to determine the impacts of the potential threats to this species ⁽¹⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

The UK Biodiversity Action Plan for this species is available at UK BAP.

Find out more

Find out more about Sowerby’s beaked whale and its conservation:

• The Beaked Whale Resource - Sowerby’s beaked whale:
  http://www.beakedwhaleresource.com/bwsowerbys.htm
• Convention on Migratory Species - Mesoplodon bidens:
  http://www.cms.int/reports/small_cetaceans/data/m_bidens/m_bidens.htm

More information on whale conservation:

• Whale and Dolphin Conservation:
  http://www.wdcs.org/index2.php

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Glossary

Beak

In whales and dolphins, the elongated front part of the head, comprising the lower jaw and upper jaw.

Bycatch

In the fishing industry, the part of the catch made up of non-target species.

Cetacean

A whale, dolphin or porpoise.

Dorsal fin

The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans (whales, dolphins and porpoises).

Gestation

The state of being pregnant; the period from conception to birth.

References

1. IUCN Red List (October, 2012)
   http://www.iucnredlist.org/
2. Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (2009) Encyclopedia of Marine Mammals. Second Edition. Academic Press, London.
3. Jefferson, T.A., Leatherwood, S. and Webber, M.A. (1993) FAO Species Identification Guide. Marine Mammals of the World. FAO, Rome. Available at:
   ftp://ftp.fao.org/docrep/fao/009/t0725e/t0725e00.pdf
4. The Beaked Whale Resource - Sowerby’s beaked whale (October, 2012)
   http://www.beakedwhaleresource.com/bwsowerbys.htm
5. CITES (January, 2013)
   http://www.cites.org/
6. Carlström, J., Denkinger, J., Feddersen, P. and Øien, N. (1997) Record of a new northern range of Sowerby’s beaked whale (Mesoplodon bidens). Polar Biology, 17: 459-461.
7. MacLeod, C.D. et al. (2006) Known and inferred distributions of beaked whale species (Cetacea: Ziphiidae). Journal of Cetacean Research and Management, 7(3): 271-286.
8. Hooker, S. and Baird, R.W. (1999) Observations of Sowerby’s beaked whales, Mesoplodon bidens, in the Gully, Nova Scotia. The Canadian Field-Naturalist, 113(2): 273-277.
9. Ostrom, P.H., Lien, J. and Macko, S.A. (1993) Evaluation of the diet of Sowerby’s beaked whale, Mesoplodon bidens, based on isotopic comparisons among northwestern Atlantic cetaceans. Canadian Journal of Zoology, 71(4): 858-861.
10. MacLeod, C.D. (1998) Intraspecific scarring in odontocete cetaceans: an indicator of male ‘quality’ in aggressive social interactions? Journal of Zoology, 244: 71-77.
11. Cox, T.M. et al. (2006) Understanding the impacts of anthropogenic sound on beaked whales. Journal of Cetacean Research and Management, 7(3): 177-187.
12. Learmonth, J.A., MacLeod, C.D., Santos, M.B., Pierce, G.J., Crick, H.Q.P. and Robinson, R.A. (2006) Potential effects of climate change on marine mammals. Oceanography and Marine Biology: An Annual Review, 44: 431-464.