Fraser’s dolphin (Lagenodelphis hosei)
|Also known as:||Sarawak dolphin|
|French:||Dauphin De Fraser|
|Spanish:||Delfín De Borneo|
|Size||Male length: up to 2.7 m (2)|
Female length: up to 2.6 m (2)
|Weight||up to 209 kg (3)|
Classified as Least Concern (LC) on the IUCN Red List (1), and listed on Appendix II of CITES (4).
This tropical dolphin was scientifically described in 1956 from an individual washed up on a beach in Borneo (2), but was not actually recorded alive until the 1970s (5). Fraser’s dolphin can be identified by its stocky body and short beak, and by its small flippers, tail fin and triangular or slightly curved dorsal fin. The body bears a striking colour pattern, but one that varies with both age and sex. The back is brownish-grey, the lower sides of the body cream-coloured, and the belly is white or pink. A prominent black stripe runs along the side of the body from the eye to the anus; in adult males this is thick, while in adult females it is variable and in young dolphins the stripe is faint or completely absent. The same pattern occurs with a black stripe on the face; this is absent in calves and variable in females, while on adult males it is extensive and merges with the body stripe to form a ‘bandit mask’ (2).
Fraser’s dolphin is a tropical species distributed in oceans between latitudes of 30°N and 30°S (2).
Inhabits deep, oceanic waters except in places where deep water approaches the coast, such as in the Philippines and Indonesia (2).
The preference of Fraser’s dolphin for deep waters is due to the prey on which it feeds; fish, squid and crustacean species that inhabit the deeper waters of the oceans. Feeding on such food requires Fraser’s dolphin to dive down to depths of at least 250 to 500 metres to hunt. It is thought that Fraser’s dolphin itself may be occasional prey for killer whales, false killer whales and large sharks, and circular wounds caused by the peculiar cookie-cutter shark (Isistius brasiliensis) have been found on this species (2) (3).
Fraser’s dolphins are highly sociable mammals that swim around in tightly-bonded schools of 100 to 1,000 individuals (2) (6), often together with schools of melon-headed whales (Peponocephala electra), other dolphin species (2) (3), or in some areas, such as the Sulu Sea, with short-finned pilot whales (Globicephala macrorhynchus) (7). A school of Fraser’s dolphins moves quickly, on very rare occasions riding the bow waves of boats, and with members of the school frequently porpoising; the term used to describe a dolphin leaping clear of the water when surfacing to breathe (2) (3).
Mating in Fraser’s dolphin is believed to be promiscuous, and mature females give birth approximately every two years to a metre-long calf, after a gestation period of 12.5 months. Males reach sexual maturity at an age of seven to ten years, while females are able to reproduce at five to eight years of age (2).
While poorly-known, Fraser’s dolphin is believed to be reasonably abundant due to the incredibly large schools that have been observed (1). In certain areas, however, it remains vulnerable to the threat of hunting and by-catch. In the lower Antilles, Indonesia and (before its protection) the Philippines, this species has been killed by harpoon and its meat consumed or sold in local markets. Some are also taken in fisheries in Taiwan and Japan, and in many areas Fraser’s dolphin is caught unintentionally in fishing gear (2) (8).
The south-east Asian populations of Fraser’s dolphin are listed on Appendix II of the Convention on Migratory Species (CMS), meaning that this species would significantly benefit from international cooperation. CMS encourages the range states to develop agreements that will benefit the conservation of this species (9). In 1992, the Department of Agriculture of the Philippines banned the ‘taking or catching, selling, purchasing, possessing, transporting and exporting of dolphins'. This order has not stopped dolphin hunting, but seems to have decreased the sale of dolphin meat openly in the market (8). The distribution, migratory behaviour, abundance and by-catch rates of Fraser’s dolphin are poorly known (8), and thus further research into this sociable dolphin is likely to be the first step in the development of any conservation measures.
For further information on dolphins and their conservation see:
Whale and Dolphin Conservation Society:
Authenticated (19/03/08) by Dr Louella Dolar, Biologist, Tropical Marine Research for Conservation (TMRC), LLC.
- By-catch: in the fishing industry, the part of the catch made up of non-target species.
- Crustacean: belonging to a diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Gestation: the state of being pregnant; the period from conception to birth.
- Promiscuous: mating with more than one individual without forming any permanent bonds.
IUCN Red List (November, 2008)
- Dolar, M.L.L. (2002) Fraser’s dolphin. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds) Encyclopedia of Marine Mammals. Academic Press, London.
- Jefferson, T.A. and Leatherwood, S. (1994) Lagenodelphis hosei. Mammalian Species, 470: 1 - 5.
CITES (December, 2007)
- Perrin, W.F., Best, P.B., Dawbin, W.H., Balcomb, K.C., Gambell, R. and Ross, G.J.B. (1973) Rediscovery of Fraser's Dolphin Lagenodelphis hosei. Nature, 241: 345 - 350.
- Ross, G.J.B. (2006) Review of the Conservation Status of Australia’s Smaller Whales and Dolphins. Department of the Environment and Heritage, Canberra, Australia.
- Dolar, L. (2008) Pers. comm.
CMS Species Factsheet (January, 2008)
CMS (January, 2008)