Marine Mammal Species Description

Sowerby's Beaked Whale

Mesoplodon bidens

(Sowerby, 1804)

Classification

Order: Cetacea
Family: Ziphiidae
Alternate Common Names: North Sea beaked whale, cowfish.

Status: protected under MMPA

Description:

   Length: 14.8-18 ft (4.5-5.5 m)
   Weight: no known weights

Sowerby's beaked whales have a long rostrum, beak, and a small falcate dorsal fin located on the back half of their body. They have a single pair of teeth that on females and young do not project out of the gums. On males, these teeth or tusks are visible because they project above the gums 2-3 cm about a third to half way back on their jaw. They are dark gray or bluish over most of their body, with paler sides and a white belly. They generally have some scarring on their body, either lines or circular scars likely caused by cookie cutter sharks.

Habitat:

Sowerby's beaked whales occur in cold, temperate waters. Sightings of this species are rare, but some records document it in deep ocean waters of a depth about 1,804-4,921 ft (550-1,500 m). Based on sightings and stranding records these whales occur in very small schools, less than 10 individuals, pairs, or alone. Many documented pairs in stranding records are females and calves.

Feeding:

These beaked whales eat mostly fish and some squid. Most feeding by members of the genus Mesoplodon likely occurs in deep waters (>656 ft / 200 m).

Reproduction:

Females likely give birth to a single calf at a time. Gestation period is about 12 months.

Other:

Most information about this species comes from a few sightings of this species at sea and stranding records. This is the most commonly stranded species in the genus Mesoplodon. One sighting recorded dive lengths for this species to be between 12 and 28 minutes. When at the surface recorded swim speeds were documented at 1-2 knots (1.7-3.4 feet per second; 0.5-1.0 meters per second).

Distribution / Range:

Sowerby's beaked whales occur in the temperate North Atlantic Ocean. Off the coast of North America, it is typically reported from the coast of Massachusetts northward. Occasional stranding records farther south along the east coast, including Florida have been documented.

Similar species:

This species is most likely confused with other members of the beaked whale genus Mesoplodon. In the genus Mesoplodon, females of different species are hard to tell apart. Males can be distinguished by their tooth placement and beak and mouth shape.

Notes:

References:

Culik, B. 2010. Odontocetes. The toothed whales: "Mesoplodon bidens". UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm. Accessed January 2012.

Gannon D.P., J.E. Craddock, and A.J. Read. 1998. Food habits of beaked whales (Mesoplodon bidens and Ziphius cavirostris) from the northeastern U.S. In: Abstracts of the World Marine Mammal Science Conference. Monaco, 20-24th January 1998, pp 49.

Hooker S.K. and R.W. Baird. 1999. Observations of Sowerby's beaked whales, Mesoplodon bidens, in the Gully, Nova Scotia. Canadian Field Naturalist 113: 273-277.

Mead, J.G. 1999. Sowerby?s beaked whale, Mesoplodon bidens. In The Smithsonian Book of North American Mammals. Wilson, D.E. and S. Ruff, eds., 308. Smithsonian Institution in association with the American Society of Mammologists, Washington DC.

Ostrom P.H., J. Lien, and S.A Macko. 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: 858-861.

Pereira, J.N., V.C. Neves, R. Prieto, M.A. Silva, I. Cascão, C. Oliveira, M.J. Cruz, J.V. Medeiros, J.P. Barreiros, F.M. Porteiro, and D. Clarke. 2011. Diet of mid-Atlantic Sowerby's beaked whales, Mesoplondon bidens. Deep Sea Research Part I: Oceanographic Research Papers 58: 1084-1090.

Pitman, R. 2009. Mesoplodont Whales - Mesoplodon spp. In: Encyclopedia of Marine Mammals 2nd Ed. Perrin W.F., B. Würsig, and J.G.M. Thewissen, eds. Academic Press, New York, pp. 721-726.

Smithsonian Institution. 2007. Beaked Whale Identification Guide. Mesoplodon bidens. http://vertebrates.si.edu/mammals/beaked_whales/pages/mbi/mbi_sp_pg1.htm. Accessed January 2012.

Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. 2008. Mesoplodon bidens. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. www.iucnredlist.org. Downloaded on 09 January 2012.