Marine Mammal Stranding Database

Marine Mammal Species Description

True's Beaked Whale

Mesoplodon mirus

True, 1913


Order: Cetacea
Family: Ziphiidae
Alternate Common Names:

Status: protected under MMPA


   Length: 15.7-17.4 ft (4.8-5.3 m)
   Weight: around 3,100 lbs (1,400 kg)

All True's beaked whales have a small slightly falcate dorsal fin on the back half of their body, and a long rostrum. Males also have a pair of teeth that are exposed and visible close to the tip of their lower jaw. True's beaked whales are dark or medium-gray on their backs and a dark ring around their eyes. In the Northern Hemisphere, they are white underneath. In the Southern Hemisphere, the dark back only extends to around their dorsal fin. These individuals are white or light-gray from their tail to around their dorsal fin. Older individuals generally have some scarring on their body, either double parallel lines, single lines or round scars.


True's beaked whales occur in the warm temperate, deep, pelagic waters. Some observations occurred in water depths 7,218-13,451 ft (2,200-4,100 m).


True's beaked whales feed on squid and fish. Most feeding by members of the genus Mesoplodon likely occurs in deep waters (>656 ft / 200 m).


Females likely give birth to a single calf at a time.


Most information about this species comes from stranding records and a few records at sea.

Distribution / Range:

True's beaked whales occur in temperate waters of the Northern Atlantic Ocean and temperate areas of the South Atlantic and Indian Oceans of the Southern Hemisphere from South America to Australia. Along the coast of the North America, they occur from Nova Scotia, Canada, south to Florida, United States.

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.



Culik, B. 2010. Odontocetes. The toothed whales: "Mesoplodon mirus". UNEP/CMS Secretariat, Bonn, Germany. Accessed January 2012

Mead, J.G. 1999. True's beaked whale, Mesoplodon mirus. In The Smithsonian Book of North American Mammals. Wilson, D.E. and S. Ruff, eds., 313-314. Smithsonian Institution in association with the American Society of Mammologists, Washington DC.

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.

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 mirus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. Downloaded on 09 January 2012.

Weir, C.R., J. Stokes, C. Martin, and P. Carmeño. 2004. Three sightings of Mesoplodon species in the Bay of Biscay: first confirmed True's beaked whales (M. mirus) for the north-east Atlantic? Journal of the Marine Biological Association of the UK 84: 1095-1099.