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Irrawaddy Dolphin
Size comparison with an average human
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Orcaella
Species: O. brevirostris
Binomial name
Orcaella brevirostris
Owen in Gray, 1866[2]
Orcaella genus range map
See: Irrawaddy Dolphin
Geographic Range Map

The Irrawaddy Dolphin (Orcaella brevirostris) is a euryhaline species of Oceanic dolphin found in discontinuous sub-populations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia.


Etymology and Taxonomic History

The Irrawaddy Dolphin was first described by Sir Richard Owen in 1866 based on a specimen found in 1852, in the harbour of Visakhapatnam on the east coast of India.[3] It is one of two species in its genus. It has sometimes been listed variously in a family containing just itself and in Monodontidae and in Delphinapteridae. There is now widespread agreement to list it in the Delphinidae family.

Genetically the Irrawaddy Dolphin is closely related to the Orca. The species name brevirostris comes from the Latin meaning short-beaked. In 2005, genetic analysis showed that the Australian Snubfin Dolphin found at the coast of northern Australia forms a second species in the Orcaella genus.

Overall grey to dark slate blue, paler underneath. No distinctive pattern. Dorsal fin small and rounded behind middle of back. Forehead high and rounded; beak lacking. Broad rounded flippers. The similar species that can be found in Borneo is the Finless Porpoise, Neophocaena phocaenoides, is similar and has no back fin: the Humpback Dolphin, Sausa chinensis, is larger, has longer beak and larger dorsal fin.[3]

The several common names for Orcaella brevirostris (Latin) include: English: Irrawaddy dolphin, Local Chilika dialect: Baslnyya Magar or Bhuasuni Magar (oil yielding dolphin), Oriya: Khem and Khera[3], French: Orcelle, Spanish: Delfín del Irrawaddy, German: Irrawadi Delphin, Burmese: Labai, Indonesia: Pesut, Malay: Lumbalumba, Khmer: Ph’sout, Lao: Pha’ka and Filipino: Lampasut.[4] In Thai, one of its names is pía loma hooa baht, because its rounded head is thought to resemble the shape of a Buddhist monk's bowl, a hooa baht.[5]


Irrawaddy dolphins are similar to the Beluga in appearance, though most closely related to the Orca. They have a large melon and a blunt, rounded head, and the beak is indistinct. The dorsal fin, located about two-thirds posterior along the back, is short, blunt and triangular. The flippers are long and broad. It is lightly coloured all over, but slightly more white on the underside than the back. Adult weight exceeds 130 kg (287 lb) kg and length is 2.3 m (8 ft) m at full maturity. Maximum recorded length is 2.75 m (9 ft) of a male from Thailand.[5]



These dolphins are thought to reach sexual maturity at 7 to 9 yrs. In the Northern Hemisphere, mating is reported from December to June. Its gestation period is 14 months, giving birth to a single calf every 2 to 3 years. Length is about 1 m (3 ft) at birth. Birth weight is about 10 kg (22 lb). Weaning is after two years. Lifespan is about 30 years.


Irrawaddy dolphins communicate with clicks, creaks and buzzes at a dominant frequency of about 60 kilohertz which is thought to be used for echolocation. Bony fish and fish eggs, cephalopods, and crustaceans are taken as food. Observations of captive animals indicate that food may be taken into the mouth by suction. Irrawaddy Dolphins sometimes spit streams of water, sometimes while spyhopping, during feeding, apparently to expel water ingested during fish capture or possibly to herd fish. Some Irrawaddy Dolphins kept in captivity have been trained to do spyhopping on command. The Irrawaddy Dolphin is a slow swimmer, but swimming speed of 20–25 km/hour was reported when dolphins were being chased in a boat.[6]

It surfaces in a rolling fashion and lifts its tail fluke clear of the water only for a deep dive. Deep dive times range from 70–150 seconds to 12min. When 277 group dives were timed (time of dis-appearance of last dolphin in group to emergence of first dolphinin the group) in Laos, mean duration was 115.3 s with a range of 19 s to 7.18 min.[5] They make only occasional low leaps and never bow-ride. Groups of fewer than 6 individuals are most common, but sometimes up to 15 dolphins are seen together. [6] [7]

Interspecific competition has been observed when Orcaella was forced inshore and excluded by more specialised dolphins. It is also reported that when captive Humpback Dolphins (Sonsa chinensis) and Irrawaddy Dolphins were held together, the Irrawaddy Dolphins were frequently chased and confined to a small portion of the tank by the dominant Humpbacks. In Chilika Lake, local fishers say that when Irrawaddy Dolphins and Bottlenose Dolphins meet in the outer channel, the former get frightened and are forced to return toward the lake.[3]

Habitat and sub-populations

Irrawaddy Dolphin on Mekong River at Kratié, Cambodia

Although sometimes called the Irrawaddy River Dolphin, it is not a true river dolphin but an oceanic dolphin that lives in brackish water near coasts, river mouths and in estuaries. It has established sub-populations in freshwater rivers, including the Ganges and the Mekong as well as the Irrawaddy River from which it takes its name. Its range extends from the Bay of Bengal to New Guinea and the Philippines.

It is often seen in estuaries and bays in Borneo Island. With sightings from Sandakan in Sabah, Malaysia, to most parts of Brunei and Sarawak, Malaysia. A specimen was collected at Mahakam River in East Kalimantan.[1]

No range-wide survey has been conducted for this vulnerable species, however it appears that the worldwide population is over 7,000, with over 90% occurring in Bangladesh. Populations outside Bangladesh and India are classified as critically endangered. Known sub-populations of Irrawaddy Dolphins are found in eight places, listed here in order of population, including conservation status.

Chilka Lake, Orissa, India, habitat of Irrawaddy Dolphins
  1. Bangladesh; 5,832 (VU) in coastal waters of the Bay of Bengal[8]
  2. and 451 (VU) in the brackish Sundarbans mangrove forest[9][10]
  3. India; 138 (VU) in the brackish water Chilka Lake[11]
  4. Laos and Cambodia; 66-86 (CR) in a 190 km (118.1 mi) freshwater stretch of the Mekong River[12]
  5. Indonesia; (CR), in a 420 km (261.0 mi) stretch of the freshwater Mahakam River
  6. Philippines; about 77 (CR) in the brackish inner Malampaya Sound
  7. Myanmar; about 58-72 (CR) in a 370 km (229.9 mi) freshwater stretch of the Ayeyarwady River
  8. Thailand: less than 50 (CR) in the brackish Songkhla Lake.[1]

Interaction with Humans

Irrawaddy dolphins have a seemingly mutualistic relationship of co-operative fishing with traditional fishers. Fishers in India recall when they would call out to the dolphins, to drive fish into their nets. [13] In Myanmar, in the upper reaches of the Ayeyawady River, Irrawaddy dolphins drive fish towards fishers using cast nets in response to acoustic signals from them. In return, the Dolphins are rewarded with some of the fishers' by-catch.[14] Historically, Irrawaddy River fishers claimed that particular dolphins were associated with individual fishing villages and chased fish into their nets. A 1879 report indicates that legal claims were frequently brought into native courts by fishers to recover a share of the fish from the nets of a rival fisher which the plaintiffs dolphin was claimed to have helped fill.[5]


Fishers with fishnets in Bangladesh

Irrawaddy Dolphins are more susceptible to human conflict than most other dolphins who live farther out in the ocean. Drowning in gillnets is the main threat to Irrawaddy dolphins throughout their range. The majority of reported dolphin deaths in all subpopulations is due to accidental capture and drowning in gillnets and dragnets, and in the Philippines, bottom-set crabnets. In Myanmar, electrofishing and gold mining are also a serious and continuing threat. Though most fishers are sympathetic to the dolphins plight, it is difficult for them to abandon their traditional means of livelihood.[1]

In several Asian countries, Irrawaddys have been captured and trained to perform in public aquariums. The charismatic appearance and unique behaviors of Irrawaddy dolphins, including spitting water, spyhopping and fluke-slapping, make them very popular for shows in dolphinariums. The commercial motivation for using this dolphin species is high because it can live in freshwater tanks and the high cost of marine aquarium systems is avoided. The region within and nearby the species’ range has developed economically and theme parks, casinos and other entertainment venues that include dolphin shows has increased. In 2002 there were more than 80 dolphinariums in at least nine Asian countries[15]

Collateral deaths of dolphins due to blast fishing were once common in Vietnam and Thailand. In the past, the most direct threat was the killing of Irrawaddys for their oil.

The IUCN lists five of the seven subpopulations as critically endangered, primarily due to drowning in fish nets.[1] For example, the Malampaya population was first discovered and described in 1986, at the time consisting of 77 individuals. Due to anthropogenic activities, this number dwindled to 47 dolphins in 2007.[16]


Entanglement in fishnets and degradation of habitats are the primary threats to Irrawaddy Dolphins. Multiple conservation efforts are being made at international and national levels to alleviate these threats.

International efforts
Listed as Critically Endangered in Laos, Malaysia, Myanmar, Philippines, and Thailand

International protection against hunting and trade is provided by the International Union for Conservation of Nature (IUCN) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). However enforcement is the responsibility of individual countries.[1]

These dolphins are classified by the IUCN as a critically endangered species in Laos, Malaysia, Myanmar, Philippines, and Thailand and a vulnerable species in Bangladesh and India. They are thus are legally protected from hunting; however, enforcement may be poor along thousands of miles of coast line.[1] In 2004, CITES transferred the Irrawaddy dolphin from Appendix II to Appendix I, which forbids all commercial trade in species that are threatened with extinction.[17]

The UNEP-CMS Action Plan for the Conservation of Freshwater Populations of Irrawaddy Dolphins notes that multiple-use protected areas will play a key role for conserving freshwater populations of Irrawaddy dolphins. Protected areas in fresh water could be a particularly effective conservation tool and can facilitate management, due to the fidelity of the species to relatively circumscribed areas. The Action Plan provides details on strategies for mitigating by-catch that includes:

-establishing core conservation areas where gillnetting is banned or severely restricted
-promoting net attendance rules and providing training on the safe release of entangled dolphins
-initiating programs to compensate fishers for damage caused to their nets
by entangled dolphins that are safely released
-providing alternative or diversified employment options for gillnet fishers
-encouraging the use of fishing gears that do not harm dolphins,
by altering or establishing fee structures for fishing permits to make gillnetting more expensive while decreasing the fees for non-destructive gear
-experimenting with acoustical deterrents and reflective nets.[18]
National efforts

Several national efforts are resulting in the reduction of threats to local Irrawaddy Dolphin sub-populations:

Satellite image of the Sundarbans

Portions of Irrawaddy dolphin habitat in the Sundarbans mangrove forest of Bangladesh are included within 139,699 ha (539 sq mi) of 3 Wildlife sanctuaries which are part of the Sunderbans World Heritage Site. The Wildlife Conservation Society is working with the Bangladesh Ministry of Environment and Forests to create protected areas for the 6000 remaining dolphins[4][19]


The Cambodian Department of Fisheries has drafted a Royal Decree for protection of Irrawaddy dolphins in the Mekong River, which includes the designation of eight protected areas, totaling 5,721 ha (22.09 sq mi), in a 190 km (118 mi) segment of the river above Kratie.[4] The establishment of community-managed deep water Fish Conservation Zones with government support may represent the best opportunity for reducing dry season dolphin mortality from large-meshed gillnet entanglement. Efforts to establish protected areas for dolphins are currently underway.[20] in 2005 the The World Wildlife Fund (WWF) established the Cambodian Mekong Dolphin Conservation Project with support from government and local communities. The aim is to support the survival of the remaining population through targeted conservation activities, research and education.[21]


The Irrawady Dolphin (under the common name of Snubfin Dolphin, with the scientific name misspelled as Oreaella brevezastris) is included the Indian Wildlife Protection Act[22], Schedule I[23], which bans their killing, transport and sale of products.[4] A major restoration effort to open a new mouth between Chilika lake and the Bay of Bengal in 2000 was successful in restoring the lake ecology and regulating the salinity gradient in the lake waters. This has resulted in increases in the population of Irrawaddy dolphin due to increase of prey species of fish, prawn and crabs.[24]


At East Kalimantan Island, the Semayang National Park has been proposed as a Irrawaddy Dolphin Sanctuary.[4] Local conservationists have also been pressing for protection of the lake and its watershed, the Berambai Forest.[25]


Canadian conservationist Ian Baird set up the Lao Community Fisheries and Dolphin Protection Project to study the Irrawaddy dolphins in the Lao part of the Mekong. Part of this project compensated fishers for the loss of nets damaged to free entangled dolphins. This project was expanded to include Cambodia, after it was determined that the majority of the dolphin population had been killed or migrated to Laos' southern neighbour.[26] The Si Phan Don Wetlands Project has successfully encouraged river communities to set aside conservation zones and establish laws to regulate how and when fish are caught.[27]


In 2005, the Department of Fisheries established a protected area for Irrawaddy dolphins in a 74 km (46 mi)-km segment of the Ayeyarwady River between Mingun and Kyaukmyaung. Protective measures in the area include mandatory release of entangled dolphins, prohibition of the catching or killing of dolphins and trade in whole or parts of them and the prohibition of electro-fishing and gill nets more than 300 feet (91 m) long, or spaced less than 600 feet (180 m). apart.[4] Mercury poisoning and habitat loss from gold mining dregding operations in the river have been eliminated[28]


In 2000, Malampaya Sound was proclaimed a protected seascape. This is the lowest possible prioritization given to a protected area.[18] Malampaya Sound Ecological Studies Project was initiated by the WWF. With technical support provided by the project, the municipality of Taytay and the Malampaya park management developed fishery policies to minimize the threats to the Irrawaddy dolphin from by-catch capture. Gear studies and gear modification to conserve the dolphin species were implemented. The project was completed in 2007.[29] In 2007, the Coral Triangle Initiative, a new multilateral partnership to help safeguard the marine and coastal resources of the Coral Triangle, including the Irrawaddy dolphin sub-population in Malampaya Sound, was launched.[30][31]


In 2002 the Marine and Coastal Resources Department was assigned to protect rare aquatic animals such as dolphins, whales and turtles in Thai territorial waters. To protect the dolphins, patrol vessels ensure that boats stay at least 30 m (98 ft) away from dolphins and that there is no chasing of or running through schools of dolphins. Many fishers on the Bang Pakong River have been persuaded by authorities to stop shrimp fishing that area, and 30 to 40 fishing boats have been modified so they can offer dolphin sightseeing tours.[32]


In 2008, the Department of Forestry and Sarawak Forestry Cooperative in Sarawak established a protected area for Irrawaddy Dolphins in Santubong and Damai (Kuching Wetland).[4] And they are also plan to established more beach in Miri as a protected area for Irrawaddy dolphins. The protected measures in the area include prohibition of the catching or killing of dolphins and trade in whole or parts of them and the prohibition of gill nets. The government may also start small and medium research of this species at Sarawak Malaysia University with sponsorship from Sarawak Shell.


Serious students of the Irrawaddy dolphin are encouraged to pursue the many details in these references that were not included in the article above.

  1. ^ a b c d e f g Reeves, R.R., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K. (2008). Orcaella brevirostris. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 March 2009. Database entry includes a brief justification of why this species is of vulnerable.
  2. ^ "Orcaella brevirostris (Owen in Gray, 1866)". ITIS Report. Integrated Taxonomic Information System. pp. Taxonomic Serial No.: 180471. Retrieved 2008-12-27.  
  3. ^ a b c d Sinha, R.K. (May–August 2004). "The Irrawaddy Dolphins Orcaella of Chilika Lagoon, India". Journal of the Bombay Natural History Society (Mumbai, India: online edition: Environmental Information System (ENVIS), Annamalai University, Centre of Advanced Study in Marine Biology, Parangipettai - 608 502, Tamil Nadu, India) 101 ((2)): 244–251.ía+loma&hl=en&ct=clnk&cd=4&gl=us&client=safari.  
  4. ^ a b c d e f g "Proposal for inclusion of species on the appendices of the convention on the conservation of migratory species of wild animals". PROPOSALS. ENEP/CMS. 2008-08-27. Retrieved 2008-12-26.  
  5. ^ a b c d Stacey, Pam J.; Peter W. Arnold (1999-05-05). "Orcaella brevirostris". Mammalian Species (American Society of Mammalogists) (616): 1–8.  
  6. ^ a b "Irrawaddy dolphin (Orcaella brevirostris)". Arkive. Wildscreen. 2008. Retrieved 2008-12-26.  
  7. ^ Culik, Boris; Kiel, Germany (2000). "Orcaella brevirostris (Gray, 1866)". Review of small Cetaceans Distribution, Behaviour, Migration and Threats. UNEP/CMS Convention on Migratory Species. Retrieved 2008-12-26.  
  8. ^ "Large population of endangered dolphins found in Bangladesh". Times of India, Flora and Fauna (2008 Bennett Coleman & Co. Ltd.). 2008-10-11. Retrieved 2008-12-29.  
  9. ^ Smith, Brian D.; Graulik Gill (2) ; Strindberg Samantha (1) ; Ahmed Benazir (3) ; Mansur Rubaiyat (4) (2006). "Abundance of irrawaddy dolphins (Orcaella brevirostris) and ganges river dolphins (Platanista Gangetica gangetica) estimated using concurrent counts made by independent teams in waterways of the sundarbans mangrove forest in Bangladesh". Marine mammal science, Society for Marine Mammalogy (Oxford, UK: Blackwell) 22 (no3): 527–547. doi:10.1111/j.1748-7692.2006.00041.x. ISSN 0824-0469.  
  10. ^ Associated Press (2009-04-01). "Study: Bangladesh hosts 6,000 rare dolphins". Retrieved 2009-04-01.  
  11. ^ Das, Subrat (2008-02-28). "Dolphins better off in Chilika - Survey reveals dip in death toll of Irrawaddy School". The Telegraph (Calcutta): pp. Front page. Retrieved 2008-12-25.  
  12. ^ Dove, D.; Dove, V.; Trujillo, F.; Zanre, R. (2008). "Abundance estimation of the Mekong Irrawaddy dolphin Orcaella Brevirostris based on mark and recapture analysis of photoidentified individuals.". WWF Cambodia Technical Report.  
  13. ^ D’Lima, Coralie (2008). "Dolphin-human interactions, Chilika". Project summary. Whale and Dolphin Conservation Society. Retrieved 2008-12-21.  
  14. ^ Tun, Tint (2008). "Castnet Fishing with the Help of Irrawaddy Dolphins". Irrawaddy Dolphin. Yangon, Myanmar. Retrieved 2008-12-25.  
  15. ^ Vertefeuille, Jan (2004-10-08). "Irrawaddy Dolphins Gain Trade Protection Under CITES; WWF Urges Countries to Stop All Live Captures". Press release (World Wildlife Fund). Retrieved 2008-12-29.  
  16. ^ Yan, Gregg (2007-03-08). "Rare Palawan dolphins now down to 47 - WWF". Section A (Philippine Daily Inquirer): pp. 1, 6. Retrieved 2007-03-10.  
  17. ^ CITES (2004-10-14). "CITES takes action to promote sustainable wildlife". Press Release (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Retrieved 2008-12-29.  
  18. ^ a b Smith, Dr. Brian D.; submitted by Dr. William Perrin (2007-03-14). "Conservation status of Irrawaddy Dolphins". Convention on the Conservation Migratory Species of Wild Animals (Bonn, Germany: CMS/UNEP) 14th Meeting of the CMS Scientific Council.  
  19. ^
  20. ^ G. Baird, Ian; Isabel L. Beasley (2005). [The "Irrawaddy dolphin Orcaella brevirostris in the Cambodian Mekong River: an initial survey"]. Oryx (Cambridge University Press) 39: (3:): 301–310. doi:10.1017/S003060530500089X (inactive 2010-01-09). OCLC doi = 10.1017/S003060530500089X. The.  
  21. ^ WWF Greater Mekong Programme Offic (2008-10-21). "Cambodian Mekong Dolphin Conservation Project". Greater Mekong. WWF. Retrieved 2008-12-31.  
  22. ^ Parliament of India. The Indian Wildlife (Protection) Act, 1972 (Substituted by Act 44 of 1991 ed.). Ministry of Environment and Forests.  
  23. ^ The Wildlife (Protection) Act, 1972. "Schedule I". '33-A. Snubfin Dolphin (Oreaella brevezastris). Part I Mammals.  
  24. ^ USAID, ed (2007-03-15). Integrating Biodiversity and Hydrological Processes. Technical report from Phase 2 of the USAID GCP-funded initiative (FY07). Chilika, Orissa, India: Conservation International/.  
  25. ^ Kreb, Danielle (2007-01-26). "rotecting the rotecting the Mahakam Mahakam Lakes in East Kalimantan, Lakes in East Kalimantan,". 1st Wetland Link International 1st Wetland Link International –– Asia Symposium Asia Symposium, Hong Kong. Conservation Foundation for Rare Aquatic Conservation Foundation for Rare Aquatic. Retrieved 2008-12-30.  
  26. ^ Pandawutiyanon, Wiwat (2005). "Irrawaddy Dolphins Disappearing from the Mekong". Mekong Currents. IPS Asia-Pacific/Probe Media Foundation. Retrieved 2008-12-31.  
  27. ^ Cranmer, Jeff; Steven Martin, Kirby Coxon (2002). "The Far South". The Rough Guide to Laos. Rough Guides. pp. 309. ISBN 185828905X, 9781858289052.,M1.  
  28. ^ "Site Of Human-dolphin Partnership Becomes Protected Area". Science Daily (ScienceDaily LLC): pp. Science News. 2006-06-23. Retrieved 2008-12-30.  
  29. ^ WWF Philippines (2008-07-07). "Malampaya Sound Ecological Studies Project". ABOUT WWF PHILIPPINES. Retrieved 2008-12-31.  
  30. ^ Philippine information Agency (2008-06-22). "PGMA to push for sustainable management of Coral Triangle". Press release (Republic of the Philippines). Retrieved 2008-12-31.  
  31. ^ Hamann, Mark; Michelle Heupel, Vimoksalehi Lukoschek, Helene Marsh (2008-05-11). [ile "Marine Mammals"]. in ARC Centre of Excellence for Coral Reef Studies. Incorporating information about marine species of conservation concern and their habitats into a network of MPAs for the Coral Triangle region. 13. (HTML cache of [file Draft Version 2 (Word document)] ed.). Townsville, Australia: James Cook University. ile  
  32. ^ Svasti, Pichaya (2007-03-24). "The Irrawaddy dolphin". Bangkok Post (reprinted by ASEAN Biodiversity). Retrieved 2008-12-30.  


  • Encyclopedia of Marine Mammals ISBN 0-12-551340-2
  • National Audubon Society Guide to Marine Mammals of the World ISBN 0-375-41141-0
  • Whales, Dolphins and Porpoises, Mark Carwardine, ISBN 0-7513-2781-6

External links


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