Irrawaddy Dolphin
| Scientific Name | Orcaella brevirostris / heinsohni |  | |
| English Common Name | Irrawaddy dolphin / Snubfin dolphin | ||
| Taxonomy | Class: Mammalia Order: Cetacea Sub-order: Odontoceti Family: Delphinidae Genus: Orcaella Species: brevirostris / heinsohni Irrawaddy dolphins were recently split into two species, with O. brevirostris occurring in five freshwater systems and the nearshore marine waters of Southeast Asia extending along the east coast of India, and the newly described Snubfin dolphin O. heinsohni occurring in the coastal waters of northern Australia and southern Papua New Guinea. | ||
| Behaviour | Irawaddy dolphins are slow swimmers, surfacing with a leisurely roll. They are not very active at the surface except when socialising. Known to swim on their sides (similar to some of the species of River dolphins) and to “spit” a stream of water when spy-hopping. The purpose of this is unknown however it is believed to be a mechanism employed to scare the fish. Several riverine populations are known to fish co-operatively with fishers by driving the fish into the nets. | ||
| World Distribution | The Irrawaddy dolphin is patchily distributed in shallow, near-shore tropical and subtropical marine waters of the Indo-Pacific, from north-eastern Australia in the south, north to the Philippines and west to north-eastern India. Its marine distribution is concentrated in estuaries and semi-enclosed water bodies (i.e. bays and sounds), generally adjacent to mangrove forests. Freshwater populations occur in three river systems - the Mahakam of Indonesia, the Ayeyarwady (formerly Irrawaddy – where they get their name from) of Myanmar (formerly Burma) and the Mekong of Laos, Cambodia and Vietnam. Irrawaddy dolphins also occur in partially isolated brackish or freshwater bodies, including Chilka Lake in India and Songkhla Lake in Thailand. | ||
| Morphology | Irrawaddy dolphins have distinctive characteristics that allow them to be easily identified – rounded head, all grey coloration, small triangular shaped dorsal fin with a blunt tip, large paddle-like flippers, and a U-shaped blowhole that is open toward the front. They can have up to 40 teeth on their upper jaw, and 36 teeth on the lower jaw. New born Irrawaddy Dolphins are about 1 m in length and weigh about 12 kg. Adults grow between 2.1 and 2.6 metres long and weigh between 90 and 150 kg. Their diet includes fish, crustaceans and squid. | ||
| Threats | The primary threat is incidental entanglement in gill-nets. Other threats include habitat loss and human disturbance, including vessel collision. | ||
| Status | No estimate of total abundance for the species is available. However, several geographically isolated populations survive only in very low numbers. | ||
| Conservation Activities | CITES Appendix I CMS Appendix II IUCN - Ayeyarwady, Mahakam, Mekong and Songkhla Lake freshwater populations are classified as Critically Endangered. All other populations are classified as Data Deficient. | ||
