True's beaked whale - Mesoplodon mirus

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In morphology and coloration, True’s beaked whales are not known to differ substantially from other mesoplodonts, although they have a slightly bulging forehead and prominent beak.

These beaked whales are characterized by the position of the mandibular teeth at the very tip of the lower jaw. The teeth are oval in cross-section, lean forward, and are visible outside the closed mouth of adult males.

Both sexes are known to reach lengths of slightly over 5 m. Newborns are probably between 2 and 2.5 m. Weights of up to 1400 kg have been recorded.

At sea, True’s beaked whales are difficult to distinguish from other mesoplodonts. The only other species in which males have oval teeth at the tip of the lower jaw is Longman's beaked whale. However, the latter species is generally much larger and the forehead is more steeply-rising than in True’s beaked whale.

True’s beaked whales are known only from strandings in Great Britain, from Florida, United States to Nova Scotia, Canada in the North Atlantic, and from southeast Africa in the Indian Ocean.

There is almost no information available on the natural history of this species of beaked whale.

Stranded animals have had squid (Loligo sp.) in their stomachs.

Almost no information is available on the threats and status of this species; True’s beaked whales are currently ‘Data Deficient’ (IUCN) and ‘Not Listed’ (ESA).

• iOBIS
• World Register of Marine Species (WoRMS)
• Encyclopedia of Life
• Catalog of Life
• Integrated Taxonomic Information System (ITIS)
• Barcode of Life

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.

Houston, J. 1990. Status of True’s beaked whale, Mesoplodon mirus, in Canada. Canadian Field-Naturalist 104:135-137.

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.