True's beaked whale (Mesoplodon mirus)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



Mesoplodon mirus is a toothed whale and can be recognised as such by the single blowhole and the presence of teeth (rather than baleen). It is a member of the beaked whale family with the characteristic V-shaped crease on the throat and the short dorsal fin set relatively far back. True's beaked whale is a small beaked whale that can reach up to 5.3 m in length. The lower jaw has a single pair of teeth (exposed only in adult males). The smooth forehead rises at a shallow angle and is bulging in appearance. It has a distinct beak and the mouthline is curved down at rear. True's beaked whale has a grey dorsal and lateral colouration with a lighter belly and darker areas around the eyes. Adults are often covered with scratches and scars.

Recorded distribution in Britain and Ireland

Expected to occur west of the Outer Hebrides and west of Ireland.

Global distribution



True's beaked whale is an oceanic species that may be seen at the surface but little is known on what depth they may dive to.

Depth range


Identifying features

  • Up to 5.3 m in length.
  • Small dorsal fin two-thirds down the body.
  • Distinct, moderately long beak.
  • Small head with shallow rising and smoothly bulging forehead.
  • Pair of V-shaped throat grooves.
  • Mouthline curved down at the rear.
  • Dark marking around the eyes.
  • Teeth at front of the mouth.

Additional information

True's beaked whale may be confused with Sowerby's beaked whale Mesoplodon bidens but can be recognised by its bulging but smooth forehead and its slightly shorter beak. Little is known about the aggregational behaviour of True's beaked whales but it is not expected to differ from similar species such as Mesoplodon bidens (Kinze, 2002).


  1. Bruyns, W.F.J.M., 1971. Field guide of whales and dolphins. Amsterdam: Publishing Company Tors.

  2. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  3. Jefferson, T.A., Leatherwood, S. & Webber, M.A., 1994. FAO species identification guide. Marine mammals of the world. Rome: United Nations Environment Programme, Food and Agriculture Organization of the United Nations.

  4. Kinze, C. C., 2002. Photographic Guide to the Marine Mammals of the North Atlantic. Oxford: Oxford University Press.

  5. Reid. J.B., Evans. P.G.H., Northridge. S.P. (ed.), 2003. Atlas of Cetacean Distribution in North-west European Waters. Peterborough: Joint Nature Conservation Committee.


  1. NBN (National Biodiversity Network) Atlas. Available from:

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-07-14


This review can be cited as:

Barnes, M.K.S. 2008. Mesoplodon mirus True's beaked whale. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 14-07-2024]. Available from:

Last Updated: 02/06/2008