Blue whale (Balaenoptera musculus)

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



The blue whale Balaenoptera musculus is a baleen whale and can be recognised as such by the plates of baleen (rather than teeth) suspended from the upper jaw and the two blowholes on the upper body. The blue whale is slender bodied and, being the largest whale species, can reach up to 33 m in length. It is a member of the rorqual family with the characteristic ventral pleats of skin under the eye and the relatively flat and broad jaw. The ventral pleats extend beyond the navel. The small flippers are less than one-fifth of the body length. It has only one prominent ridge on the snout. The head is broad and U-shaped, and the head colouration is symmetrical. The dorsal fin is very small and set far back on the body. The blue whale has a mottled dorsal and lateral colouration with white under the flippers.

Recorded distribution in Britain and Ireland

Occasionally seen off the western coasts of Ireland and possibly further north.

Global distribution



The blue whale is an open ocean whale, not often seen near the coast in north-west Europe. It can be found at the surface or diving down to 150 metres.

Depth range


Identifying features

  • Up to 33 m in length.
  • Uniform mottled grey dorsal and lateral colouration; white under the flippers.
  • Broad tail flukes from tip to tip.
  • Very small dorsal fin set far back on the body.
  • Up to 88 ventral pleats ending past the navel.

Additional information

The blue whale can be confused with the fin whale Balaenoptera physalus but is recognised by its broad and U-shaped head, a very small dorsal fin that is set far back on the body, and symmetrical head colouration. Blue whales are usually found alone or in pairs, although in feeding areas up to a dozen have been seen together. It rarely breeches, and when diving, it will often show the tail flukes. Dives may last up to 30 minutes long (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.

  6. Smith, T.D. (ed.), 2008. World Whaling Database: Individual Whale Catches, North Atlantic. In: M.G Barnard & J.H Nicholls, HMAP Data Pages., 2008-03-13


  1. Glasgow Museums BRC, 2017. Mammal records for Clyde Faunal Area, 1850 to 2007. Occurrence dataset: accessed via on 2018-09-27.

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

  3. North East Scotland Biological Records Centre, 2017. NE Scotland marine mammal records 1800-2010. Occurrence dataset: accessed via on 2018-10-01.

  4. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-05-21


This review can be cited as:

Barnes, M.K.S. 2008. Balaenoptera musculus Blue 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 21-05-2024]. Available from:

Last Updated: 24/06/2008