True's beaked whale

Content Cover Image

True's beaked whale. Source: Wurtz-Artescienza

True's beaked whale (Mesoplodon mirus) is one of 21 species of beaked whales (Hyperoodontidae or Ziphiidae), medium-sized whales with distinctive, long narrow beaks and dorsal fins which are set far toward the posterior. They are marine mammals within the order of cetaceans.

caption True's beaked whale. Source: FAO
caption Size comparison of an average human against True's beaked whale. Source: Chris Huh

Conservation Status:
Data Deficient

Scientific Classification

Kingdom: Animalia
Phylum:--- Chordata
Class:------ Mammalia
Order:-------- Cetacea
Family:-------- Hyperoodontidae
Genus:--------- Mesoplodon
Species:-------- Mesoplodon mirus (True, 1913)

Common Names:

True's beaked whale

True's beaked whale is a toothed whale and can be recognised as such by the single blowhole as well as the presence of teeth (rather than baleen). 

Because of the highly disjunctive distribution patches of True's beaked whale, it is possible that the northern and southern hemisphere temperate ocean populations are actually distinct species or subspecies. Threats to the species include bycatch and underwater noise pollution.

Physical Description

This species 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 meters 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.

True's beaked whale may be confused with Sowerby's beaked whale 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 Sowerby's beaked whale (Kinze, 2002). Very few True's individuals have been weighed or measured. The longest male on record measured 5.3 m; the longest female, which had body mass of 1394 kilograms, and was 5.1 m long.

Distribution and Movements

Found along the North American coastline from Nova Scotia to the Bahamas, True’s beaked whale also inhabits temperate waters off the coast of Europe, and there are records of the species from near Australia and South Africa.

The IUCN Red List adds:

True's beaked whales appear to have a disjunct, anti-tropical distribution (Mead 1989, MacLeod et al. 2006). In the Northern Hemisphere, they are known only in the North Atlantic, from records in eastern North America (Nova Scotia to Florida), Bermuda, Europe to the Canary Islands, the Bay of Biscay, and the Azores. They also occur at least in the southern Indian Ocean, from South Africa, Madagascar, southern Australia and the Atlantic coast of Brazil (MacLeod et al. 2006). The species does not generally occur within 30° north or south of the equator, which may indicate that the northern and the southern subpopulations are isolated from one another. This is supported by morphological and colouration differences (Ross 1969, Ross 1984).


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.

Feeding Habits

Squid beaks have been found in the stomachs of stranded animals, but no fish have been found in one control study.

Threats and Conservation Status

The IUCN Red List reports:

Almost no information is available on the threats and status of this species. It appears never to have been hunted. Entanglement in fishing gear, especially gillnets in deep water (e.g., for billfish and tuna), is probably the most significant threat.

This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006)

As a temperate water species, the strap-toothed whale may be vulnerable to the effects of climate change as ocean warming may result in a shift or contraction of the species range as it tracks the occurrence of its preferred water temperatures (Learmonth et al. 2006). The effect of such changes in range size or position on this species is unknown.

Evidence from stranded individuals of Mesoplodon mirus indicates that they have swallowed discarded plastic items. This may eventually lead to death (e.g. Scott et al. 2001).

Further Reading

  1. 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 2010. IUCN Red List of Threatened Species. Version 2010.4. . Downloaded on 15 May 2011.
  2. Balcomb, K. C. and Claridge, D. E. 2001. A mass stranding of cetaceans caused by naval sonar in the Bahamas. Bahamas Journal of Science 8(2): 2-12.
  3. Bruyns, W.F.J.M., (1971). Field guide of whales and dolphins. Amsterdam: Publishing Company Tors.
  4. Banks, R. C., R. W. McDiarmid, A. L. Gardner, and W. C. Starnes. 2003. Checklist of Vertebrates of the United States, the U.S. Territories, and Canada
  5. Banks, R. C., R. W. McDiarmid, and A. L. Gardner. 1987. Checklist of Vertebrates of the United States, the U.S. Territories, and Canada. Resource Publication, no. 166. 79
  6. Borges, P.A.V., Costa, A., Cunha, R., Gabriel, R., Gonçalves, V., Martins, A.F., Melo, I., Parente, M., Raposeiro, P., Rodrigues, P., Santos, R.S., Silva, L., Vieira, P. & Vieira, V. (Eds.) (2010). A list of the terrestrial and marine biota from the Azores. Princípia, Oeiras, 432 pp.
  7. Cox, T. M., Ragen, T. J., Read, A. J., Vos, E., Baird, R. W., Balcomb, K., Barlow, J., Caldwell, J., Cranford, T., Crum, L., D'Amico, A., D'Spain, A., Fernández, J., Finneran, J., Gentry, R., Gerth, W., Gulland, F., Hildebrand, J., Houser, D., Hullar, T., Jepson, P. D., Ketten, D., Macleod, C. D., Miller, P., Moore, S., Mountain, D., Palka, D., Ponganis, P., Rommel, S., Rowles, T., Taylor, B., Tyack, P., Wartzok, D., Gisiner, R., Mead, J. and Benner, L. 2006. Understanding the impacts of anthropogenic sound on beaked whales. Journal of Cetacean Research and Management 7(3): 177-187.
  8. Fernández, A., Edwards, J. F., Rodriguez, F., Espinosa, A., De Los Monteros, Herraez, P., Castro, P., Jaber, J. R., Martin, V. and Arebelo, M. 2005. "Gas and fat embolic syndrome" involving a mass stranding of beaked whales (family Ziphiidae) exposed to anthropogenic sonar signals. Veterinary Pathology 42: 446-457.
  9. Gomercic, H., Gomercic, M. D., Gomericic, T., Lucic, H., Dalebout, M., Galov, A., Skrtic, D., Curkovic, S., Vukovic, S. and Huber, D. 2006. Biological aspects of Cuvier's beaked whale (Ziphius cavirostris) recorded in the Croatian part of the Adriatic Sea. European Journal of Wildlife Research 52(3): 182-187.
  10. Guiry, M.D. & Guiry, G.M. (2011). Species.ie version 1.0 World-wide electronic publication, National University of Ireland, Galway (version of 15 March 2010).
  11. Houston, J. 1990. Status of True's beaked whale, Mesoplodon mirus, in Canada. Canadian Field-Naturalist 104: 135-137.
  12. Howson, C.M. & Picton, B.E. (ed.), (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.]
  13. 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.
  14. Jepson, P. D., Arebelo, M., Deaville, R., Patterson, I. A. P., Castro, P., Baker, J. R., Degollada, E., Ross, H. M., Herraez, P., Pocknell, A. M., Rodriguez, F., Howie, F. E., Espinosa, A., Reid, R. J., Jaber, J. R., Martin, V., Cunningham, A. A. and Fernandez, A. 2003. Gas-bubble lesions in stranded cetaceans. Nature 425: 575-576.
  15. Kinze, C. C., (2002). Photographic Guide to the Marine Mammals of the North Atlantic. Oxford: Oxford University Press.
  16. Learmonth, J. A., Macleod, C. D., Santos, M. B., Pierce, G. J., Crick, H. Q. P. and Robinson, R. A. 2006. Potential effects of climate change on marine mammals. Oceanography and Marine Biology: An Annual Review 44: 431-464.
  17. MEDIN (2011). UK checklist of marine species derived from the applications Marine Recorder and UNICORN, version 1.0.
  18. Macleod, C. D., Perrin, W. F., Pitman, R. L., Barlow, J., Balance, L., D'amico, A., Gerrodette, T., Joyce, G., Mullin, K. D., Palka, D. L. and Waring, G. T. 2006. Known and inferred distributions of beaked whale species (Ziphiidae: Cetacea). Journal of Cetacean Research and Management 7(3): 271-286.
  19. MacLeod, C. D., Santos, M. B., Lopez, A. and Pierce, G. J. 2005. Relative prey size consumption in toothed whales: implications for prey selection and level of specialization. Marine Ecology Progress Series 326: 295-307.
  20. Malakoff, D. 2002. Suit ties whale deaths to research cruise. Science 298: 722-723.
  21. Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed whales, pp. 349-430. Academic Press.
  22. Mead, James G., and Robert L. Brownell, Jr. / Wilson, Don E., and DeeAnn M. Reeder, eds. 2005. Order Cetacea. Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vol. 1. 723-743
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  25. 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.
  26. Perrin, W. (2011). Mesoplodon mirus True, 1913. In: Perrin, W.F. World Cetacea Database. Accessed through: Perrin, W.F. World Cetacea Database on 2011-05-05
  27. Ramos, M. (ed.). 2010. IBERFAUNA. The Iberian Fauna Databank
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  29. Ross, G. J. B. 1969. Evidence for a Southern Breeding Population of True's Beaked Whale. Nature 222: 585.
  30. Ross, G. J. B. 1984. The smaller cetaceans of the south east coast of southern Africa. Annals of the Cape Provincial Museums (Natural History) 15: 173-410.
  31. Scott, M. D., Hohn, A. A., Westgate, A. J., Nicolas, J. R., Whitaker, B. R. and Campbell, W. B. 2001. A note on the release and tracking of a rehabilitated pygmy sperm whale (Kogia breviceps). Journal of Cetacean Research and Management 3(1): 87-94.
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  34. Wang, J. Y. and Yang, S. C. 2006. Unusual cetacean stranding events of Taiwan in 2004 and 2005. Journal of Cetacean Research and Management 8: 283-292.
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  38. van der Land, J. (2001). Tetrapoda, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 375-376
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Life, E. (2011). True's beaked whale. Retrieved from http://www.eoearth.org/view/article/165909


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