Orcaella brevirostris

– Data Deficient

Taxonomy

Kingdom:	ANIMALIA
Phylum:	CHORDATA
Class:	MAMMALIA
Order:	CETACEA
Family:	DELPHINIDAE
Scientific Name:	Orcaella brevirostris
Species Authority:	(Owen in Gray, 1866)
Infra-specific Taxa Assessed:	See Orcaella brevirostris (Ayeyarwady River subpopulation) See Orcaella brevirostris (Mahakam subpopulation) See Orcaella brevirostris (Malampaya Sound subpopulation) See Orcaella brevirostris (Mekong River subpopulation) See Orcaella brevirostris (Songkhla Lake subpopulation)
Common Name/s:	IRRAWADDY DOLPHIN (Eng) SNUBFIN DOLPHIN (Eng) ORCELLE (Fre) DELFÍN DEL IRRAWADDY (Spa)
Taxonomic Notes:	This assessment currently includes the Australasian subpopulation which has been split off as a new species.

Assessment Information

Red List Category & Criteria:

DD ver 2.3 (1994)

Year Assessed:

1996

Annotations:

Needs updating

Assessor/s:

Cetacean Specialist Group

Justification:

Extract from Reeves et al. (2003, pp. 43): "The distribution of Irrawaddy Dolphins overlaps areas of intensive use by humans. For example, in the Mekong delta, rows of netting stretch across many channels, providing a likely explanation for the lack of recent dolphin sightings in the area even though several skulls are preserved in local "whale temples" (Smith et al. 1997a). The species apparently has been seriously depleted in parts of Thailand (Andersen and Kinze in IWC 1994, p.110). Incidental mortality in fisheries (e.g., gillnets, explosives) is likely the principal cause of depletion, although the degradation of river and lake systems caused by damming, forestry practices, and mining could also play an important role (Baird and Mounsouphom 1997, Smith et al. 1997b, Kreb 1999, Smith and Hobbs 2002). Live-capture for captive display poses an additional pressure on small, localized [sub]populations such as those in the Mahakam River and possibly the Ayeyarwady River. In Australia, Irrawaddy dolphins are killed in anti-shark nets and gillnets (Parra et al. 2002).

Recent surveys indicate dramatic declines in range and abundance of the Mekong and Mahakam freshwater [sub]populations (IWC 2001). The latter was classified as Critically Endangered in the Red List in 2000 after surveys found only a few tens of dolphins, confined to an approximately 300km segment of river (Kreb 1999, 2002). Another small group of animals living at the head of Malampaya Sound in Palawan, Philippines, appears to be geographically isolated (Dolar et al. 2002). If this proves to be the case, the Malampaya population should also be classified as Critically Endangered simply by virtue of its low numbers. Surveys in 2001 resulted in an estimate of 77 individuals (CV 27.4%) confined to a 133km² area of the inner sound (B.D. Smith, unpublished data)."

History:

1988	-	Insufficiently Known (IUCN Conservation Monitoring Centre 1988)
1990	-	Insufficiently Known (IUCN 1990)
1994	-	Insufficiently Known (Groombridge 1994)

Geographic Range

Range Description:

Extract from Reeves et al. (2003, pp. 43): "Irrawaddy Dolphins are patchily distributed in shallow, near-shore tropical and subtropical marine waters of the Indo-Pacific, from northern Australia in the south, north to the Philippines (Dollar et al. 2002) and west to northeastern India (Stacey and Leatherwood 1997, Stacey and Arnold 1999). Their distribution is centered in estuaries and mangrove areas. Freshwater subpopulations occur in three river systems; the Mahakam of Indonesia, the Ayeyarwady (formerly Irrawaddy) of Myanmar (formerly Burma), and the Mekong of Laos, Cambodia, and Viet Nam. Irrawaddy Dolphins also occur in completely or partially isolated brackish water bodies, including Chilka Lake in India and Songkhla Lake in Thailand. The animals in northern Australian waters are morphologically distinct from those in Asia (Beasley et al. 2002)."

Countries:

Native:

Australia; Bangladesh; Cambodia; India; Indonesia; Lao People's Democratic Republic; Malaysia; Myanmar; Papua New Guinea; Philippines; Thailand; Timor-Leste; Viet Nam

Uncertain presence and origin:

Brunei Darussalam; Singapore

FAO Marine Fishing Areas:

Native:

Indian Ocean-eastern; Pacific-western central

Habitat and Ecology

System:

Freshwater; Marine

List of Habitats:

1.7	Forest - Subtropical/Tropical Mangrove Vegetation Above High Tide Level
5.1	Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
5.14	Wetlands (inland) - Permanent Saline, Brackish or Alkaline Lakes
9.1	Marine Neritic - Pelagic
9.10	Marine Neritic - Estuaries

Threats

List of Threats:

1.1.2.2	Habitat Loss/Degradation - Agriculture - Wood plantations - Large-scale (ongoing)
1.3.1	Habitat Loss/Degradation - Extraction - Mining (ongoing)
1.3.2.2	Habitat Loss/Degradation - Extraction - Fisheries - Artisinal/small-scale (ongoing)
1.4.6	Habitat Loss/Degradation - Infrastructure development - Dams (ongoing)
3.5.3	Harvesting (hunting/gathering) - Cultural/scientific/leisure activities - Regional/international trade (ongoing)
4.1.1.2	Accidental mortality - Bycatch - Fisheries-related - Netting (ongoing)
4.1.1.4	Accidental mortality - Bycatch - Fisheries-related - Dynamite (ongoing)

Bibliography

Bibliography:

Baird, I.G. and Mounsouphom, B. 1997. Distribution, mortality, diet and conservation of Irrawaddy Dolphins (Orcaella brevirostris Gray) in Lao PDR. Asian Marine Biology 14: 41–48.

Beasley, I., Arnold, P. and Heinsohn, G. 2002. Geographical variation in skull morphology of the Irrawaddy Dolphins, Orcaella brevirostris (Owen in Gray, 1866). Raffles Bulletin of Zoology, Supplement: 15–34.

Dolar, M.L.L., Perrin, W.F., Gaudiano, J.P., Yaptinchay, A.A.S.P. and Tan, J.M.L. 2002. Preliminary report on a small estuarine population of Irrawaddy Dolphins Orcaella brevirostris in the Philippines. Raffles Bulletin of Zoology, Supplement: 155–160.

Groombridge, B. (ed.) 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland.

IUCN Conservation Monitoring Centre. 1988. 1988 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 1990. 1990 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IWC. 1994. Report of the scientific committee. Report of the International Whaling Commission 44: 41–201.

IWC. 2001. Annex K. Report of the standing sub-committee on small cetaceans. Journal of Cetacean Research and Management 3 (Supplement): 263–291.

Kreb, D. 1999. Observations on the occurrence of Irrawaddy Dolphin, Orcaella brevirostris, in the Mahakam River, East Kalimantan, Indonesia. Zeitschrift für Säugetierkunde 64: 54-58.

Kreb, D. 2002. Density and abundance estimates of the Irrawaddy Dolphin, Orcaella brevirostris, in the Mahakam River of East Kalimantan, Indonesia: a comparison of survey techniques. Raffles Bulletin of Zoology, Supplement: 85–95.

Parra, G.J., Azuma, C., Preen, A.R., Corkeron, P.J. and Marsh, H. 2002. Distribution of Irrawaddy Dolphins, Orcaella brevirostris, in Australian waters. Raffles Bulletin of Zoology, Supplement: 141–154.

Reeves, R.R., Smith, B.D., Crespo, E.A. and di Sciara, G.N. (compilers) 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.

Smith, B.D. and Hobbs, L. 2002. Status of Irrawaddy Dolphins Orcaella brevirostris in the upper reaches of the Ayeyarwady River, Myanmar. Raffles Bulletin of Zoology, Supplement: 67–73.

Smith, B.D., Jefferson, T.A., Leatherwood, S., Ho, D.T., Thuoc, C.V.,and Quang, L.H. 1997a. Investigations of marine mammals in Vietnam. Asian Marine Biology 4: 145–172.

Smith, B.D., Thant, U.H., Lwin, J.M. and Shaw, C.D.1997b. Investigation of cetaceans in the Ayeyarwady River and northern coastal waters of Myanmar. Asian Marine Biology 14: 173–194.

Stacey, P. J. and Leatherwood, S. 1997. The Irrawaddy Dolphin, Orcaella brevirostris: a summary of current knowledge and recommendations for conservation action. Asian Marine Biology 14: 195–214.

Stacey, P.J. and Arnold, P.W. 1999. Orcaella brevirostris. Mammalian Species (American Society of Mammalogists) 616: 1-8.

Citation:	Cetacean Specialist Group 1996. Orcaella brevirostris. In: IUCN 2007. 2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 06 July 2008.
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