Taxonomy & Nomenclature
Physical Description / Field Identification
Sowerby’s beaked whales have the typical Mesoplodon body shape, but tend to have a very long (for mesoplodonts) beak and a bulge on the forehead. The two teeth of adult males erupt from the middle of the lower jaw, and are visible outside the closed mouth, although they are not particularly large.
Coloration is not well known, but generally appears charcoal gray, with a lighter belly. White or light gray spots are common on the body of adults; however, young animals have less spotting. Males reach lengths of at least 5.5 m and females, 5.1 m. Newborns average 2.4 m.
Can be Confused With
Sowerby’s beaked whales can be easily confused with other species of Mesoplodon; even bulls would be difficult to distinguish from related species at sea. The limited distribution will help narrow the choices.
These beaked whales are known only from the colder waters of the North Atlantic, from at least Massachusetts to Labrador in the west, and from Iceland to Norway in the east. The range is known to include the Baltic Sea, but not the Mediterranean. The North Sea appears to be the center of abundance. There is a single record from the Gulf of Mexico, but this may represent an extralimital wandering.
Ecology and Behavior
Almost nothing is known of the natural history of this species beyond what has been learned from strandings, which have involved singles and pairs. However, in several groups observed at sea off Nova Scotia, groups ranged in size from 3-10, and dives lasted 12-28 minutes. The breeding season appears to be late winter to spring.
Feeding and Prey
Sowerby’s beaked whales feed on squid and small fish.
Threats and Status
There is little specific information on the status or threats of this species; however, some are known to have been killed by hunters in Newfoundland. Sowerby’s beaked whales are currently ‘Data Deficient’ (IUCN) and ‘Not Listed’ (ESA).
Dalebout, M. L. 2002. Species identity, genetic diversity, and molecular systematic relationships among the Ziphiidae (beaked whales). Ph.D. dissertation, University of Auckland, New Zealand.
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. 1989. Beaked whales of the genus Mesoplodon. pp. 349-430 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic Press.
Pitman, R.L. 2002. Mesoplodont whales Mesoplodon spp. pp. 738-742 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.