Lagenorhynchus albirostriswhite-beaked dolphin

Last updated:

Geographic Range

North Atlantic and adjacent waters from Davis Strait and Cape Cod to Barents Sea, the Baltic Sea, Portugal and possibly Turkey (Nowak 1999).

Habitat

Lagenorhynchus albirostris generally occurs in cool waters. This species moves north into Davis Strait during the spring and summer, then moves back in the autumn and spends the winter as far south as Cape Cod (Nowak 1999).

Physical Description

The white-beaked dolphin has a robust body, with a short, thick beak about 5-8 cm long in adults. The beak is distinctly set off from the melon. The dorsal fin is at mid-body. It is proportionally large (up to 15% of body length), often rounded at the peak, and strongly recurved. Both the dorsal fin and the flukes apparently decrease in size relative to other body dimensions as the dolphin ages. The pointed flippers can be up to 19% of the total adult length. The thickened tail stock tapers gradually, in marked contrast to that of the Atlantic white-sided dolphin (Reeves 1999).

The coloration of this species shows considerable variability. The beak of most white-beaked dolphins is white, often mottled with light grey or with greyish or blackish spots, but in some, it is almost entirely grey (though paler than the head). The dark dorsal field anterior to the dorsal fin is sometimes separated from the dark melon by a transverse light grey stripe, a brownish-grey patch or a bold whitish "chevron" around and behind the blowhole. It may extend downwards from the melon to encircle the eye. In front of the dark grey zones on the sides, there is a paler grey, rather ill-defined thoracic patch. Above and behind this patch, between the dark grey dorsal and lateral fields, the body is varying shades of light grey to nearly white. The whitish or light grey flank pigmentation extends dorsally onto the back behind the dorsal fin. The underside is white, with the white central part of the abdomen forming a narrow band between two pale grey patches. The flukes, the tail stock immediately in front of the flukes, and the flippers, are generally dark, but often spotted or marbled with white near the insertions of the flippers and on the undersides of the flukes. Four to six hair follicles are present on each side of the upper jaw. Hairs are present on the upper lip of young individuals (Reeves et al. 1999).

  • Average mass
    200 kg
    440.53 lb

Reproduction

Calves are born between June and September. At birth they are about 115 cm long and weigh 40 kg. They reach sexual maturity at a length of 1.95 m ( http://ourworld.compuserve.com/homepages/jaap/lag-albi.htm).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual

Behavior

Group size is generally 1-35 individuals, with occasional herds of several hundred, although a group as large as 1500 has been reported. Such large groups are exceptional, however, and probably consists of many smaller subgroups. White-beaked dolphins frequently ride the bow and stern waves of vessels. They are acrobatic at the surface, often leaping vertically from the water. They seem attracted to small boats, and this can bias the results of vessel surveys (Reeves et al. 1999).

Communication and Perception

Food Habits

The principle prey of the white-beaked dolphin includes clupeids, gadids and hake. Other fish, squid, octopus and benthic crustaceans are also eaten (Reeves et al. 1999).

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Conservation Status

White-beaked dolphins are hunted along the coasts of several Northern Atlantic countries including Norway, Iceland and Newfoundland. Like other North Atlantic marine mammals, white-beaked dolphins are poisoned by organochlorides, other anthropogenic compounds, and heavy metals. The impact of these factors on the population are unknown. Some populations have apparently grown in the last thirty years or so, while others (including those in the Gulf of Maine) have declined (Reeves 1999).

Other Comments

Observers frequently confuse Atlantic white-sided dolphins with white-beaked dolphins since the latter also have conspicuous areas of white on their flanks. It has been reported that the white-beaked dolphin is by far the commonest dolphin in Shetland coastal waters, as exemplified by ferry crossings between Grutness and Fair Isle and research cruises that have been conducted east of Shetland (Shetland Wildlife 1999).

Contributors

Barbara Lundrigan (author), Michigan State University, Diana Tarr (author), Michigan State University.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

piscivore

an animal that mainly eats fish

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

References

1999. "White-beaked dolphin" (On-line). Accessed December 10, 1999 at http://ourworld.compuserve.com/homepages/jaap/lag-albi.htm.

Nishiwaki, M. 1972. General Biology. Pp. 3-204 in S Ridgway, ed. Mammals of the Sea: Biology and Medicine. Springfield, IL: Thomas Books.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore and London: The John Hopkins University Press.

Reeves, R., C. Smeenk, C. Kinze, R. Brownell, Jr., J. Lien. 1999. White-beaked Dolphin. Pp. 1-30 in S Ridgway, R Harrison, eds. Handbook of Marine Mammals, Vol 6. London: Academic Press.

Shetland Wildlife, 1999. "Shetland Wildlife-News & Information on the Wildlife of Shetland" (On-line). Accessed December 10, 1999 at http://www.wildlife.shetland.co.uk/.