Long-beaked common dolphin (Delphinus capensis)

French: Dauphin Commun A Bec Large
Spanish: Delfín Común A Pico Largo
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderCetartiodactyla
FamilyDelphinidae
GenusDelphinus (1)
SizeMale length: 2 - 2.6 m (2)
Female length: 1.9 - 2.3 m (2)

Classified as Data Deficient (DD) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

Since the mid-1990s, the common dolphin has been split into two species, the long-beaked common dolphin and the short-beaked common dolphin (2) (4). As implied by their respective names, beak length is important for distinguishing between the two species, but is not the only defining feature (2). Based on specimens from California, both species have a bold, light and dark hour-glass pattern on the side of the body, forming a V below the dorsal fin, but the colouration of the long-beaked species is noticeably muted. A slightly curved dorsal fin is equally characteristic of both species but the body of the long-beaked common dolphin is more slender and the head is less rounded (2) (5). The long-beaked dolphin has more teeth than any other dolphin with 47 to 67 pairs lining each jaw (6).

Although an exceptionally long-beaked form occurring in parts of the Indo-Pacific is sometimes considered to be a separate species, the most recent evidence indicates that it is a subspecies of the long-beaked common dolphin, Delphinus capensis tropicalis (1) (4) (7).

There is growing evidence that several scattered populations, currently labelled as long-beaked common dolphins, may have actually evolved independently of each other in response to similar ecological conditions. The implications of this convergent theory are that these populations potentially represent different subspecies of the short-beaked common dolphin, or even unique species. Supporters of this alternative taxonomic view point to the fact that, in parts of the long-beaked common dolphin’s described range, it is very difficult to separate the two species of common dolphin on either morphological or genetic grounds (8). Needless to say, more research is needed before the true taxonomic status of this species will be revealed (9).

As the long-beaked common dolphin was only given distinct species status in 1994, its exact distribution in the three major oceans is yet to be fully identified (1) (5). The nominate subspecies, D. c. capensis is known from disjunctive populations on the east and west coast of South America, southern Mexico, central California, West Africa, South Africa, southern Japan, Korea, northern Taiwan and possibly China (1). The less widespread subspecies, D. c. tropicalis, is known only from the northern Indian Ocean and Southeast Asia (5).

The long beaked common dolphin is generally found within 180 km of the coast in warm temperate and tropical waters. It rarely occurs near islands that are far from mainland coasts (1) (5).

Besides what is known about common dolphins in general, little is yet known about the specific behaviour of the long-beaked dolphin (2). Common dolphins are amongst the most gregarious mammals and are sometimes seen in groups of more than 1,000 individuals (4) (6). These large schools may comprise smaller social units of 10 to 30 closely related dolphins (5). At the surface, common dolphins are extremely energetic, moving in and out of the water in a series of high speed jumps, known as porpoising, or leaping vertically to create a dramatic splash on landing (5) (6). Speeds in excess of 40 kilometres per hour can be reached and these dolphins will often ride the bow waves of ships (4) (5).

Common dolphins typically dive for two to three minutes in the pursuit of food and can reach depths of up to 280 metres (4). A large geographic range accounts for a diverse mix of prey, that includes various species of small schooling fish and squid (4) (5) (6).

Breeding usually takes place between spring and summer, with a sexually mature female giving birth every two or three years. The calf is born following a gestation period of nine to eleven months and is weaned after around six months. The age at which sexual maturity is reached appears to vary with region such that males may take two to seven years and females may take between three and twelve years. The maximum life expectancy is estimated to be around 22 years (4) (5).

Despite having a smaller distribution than the short-beaked dolphin and probably a far smaller overall population, the long-beaked dolphin is thought to still have a relatively widespread population in the high tens of thousands or even low hundreds of thousands (1) (7). However, in some regions, such as West Africa, East Asia and the east and west coasts of South America, undetermined numbers of long-beaked dolphin are being directly exploited, or taken as incidental bycatch in other fisheries (1). In Peru and West Africa in particular, there is increasing concern about the number of long-beaked dolphin being caught and used for human food and shark-bait (1) (6) (7). Given the lack of data quantifying these impacts, the long-beaked dolphin is currently listed as Data Deficient on the IUCN Red List (1).

The long-beaked common dolphin benefits from The Pacific Offshore Cetacean Reduction Plan which was implemented in 1997 to reduce the number of cetaceans killed or injured incidentally in driftnets. Amongst other obligations, the plan requires that vessels use ‘pingers’ which send out an acoustic pulse to deter marine mammals such as the long-beaked common dolphin (6).

In West Africa, WWF are working to develop an action plan for the conservation of small cetaceans in the region. This plan is to be built around formulating and implementing protective policies and laws, and improving scientific knowledge and public awareness (10).

For further information on the conservation of cetaceans see: 

Authenticated (24/02/09) by William F. Perrin, Senior Scientist for Marine Mammals, National Marine Fisheries Service, Southwest Fisheries Science Center.


http://swfsc.noaa.gov

  1. IUCN Red List (December, 2008)
    http://www.iucnredlist.org/
  2. Carwardine, M., Hoyt, E., Fordyce, R.E. and Gill, P. (1998) Whales and Dolphins. HarperCollins Publishers, London.
  3. CITES (September, 2008)
    http://www.cites.org
  4. Nowak, R.M. (1999) Walker's Mammals of the World. Johns Hopkins University Press, Baltimore, Maryland.
  5. Perrin, W.F. (2008) Common dolphins. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds) Encyclopedia of marine mammals. Second Edition. Academic press, Amsterdam.
  6. NOAA Fisheries Service (December, 2008)
    http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/commondolphin_longbeaked.htm
  7. Reeves, R.R., Smith, B.D., Crespo, E.A. and Notarbartolo di Sciara, G. (2003) Dolphins, Whales and Porpoises: 2002–2010 Conservation Action Plan for the World's Cetaceans. IUCN/SSC Cetacean Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK.
  8. Natoli, A., Cañadas, A., Peddemors, V.M., Aguilar, A., Vaquero, C., Fernández- Piqueras, P. and Hoelzel, A.R. (2006) Phylogeography and alpha taxonomy of the common dolphin (Delphinus sp.). Journal of Evolutionary Biology, 19: 953 - 954.
  9. Perrin, W.F. (2009) Pers. comm.
  10. WWF (December, 2008)
    http://www.panda.org/about_wwf/where_we_work/africa/where/cape_verde/index.cfm?uProjectID=9F0781