Indus river dolphin
| Indus River Dolphin | |
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| Family: | Platanistidae Gray, 1846
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| Genus: | Platanista Wagler, 1830
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| Species: | P. minor
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| Binomial name | |
| Platanista minor (Lebeck, 1801); (Roxburgh, 1801)
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Platanista minor | |
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| Ranges of the Ganges River Dolphin and of the Indus River Dolphin | |
The Indus River Dolphin (Platanista minor) is a sub-species of freshwater or river dolphin found in the Indus River (and its Beas and Sutlej tributaries) of Pakistan. From the 1970s until 1998, the Ganges River Dolphin and the Indus dolphin were regarded as separate species; however, in 1998, their classification was changed from two separate species to subspecies of a single species (see taxonomy below).
Other names
- Both subspecies: South Asian River Dolphin, Blind River Dolphin, Side-swimming Dolphin
- Ganges subspecies: Gangetic Dolphin, Ganges Susu,[2] Shushuk
- Indus subspecies: Bhulan, Indus Dolphin, Indus blind dolphin
Taxonomy
The species was described by two separate authors Lebeck and Roxburgh in the year 1801 and it is unclear to whom the original description should be ascribed.[3] Until the 1970s the Indus and Ganges River Dolphins were regarded as a single species. The two populations are geographically separate and have not interbred for many hundreds if not thousands of years. Based on differences in skull structure, vertebrae and lipid composition scientists declared the two populations as separate species in the early 1970s.[4] In 1998 the results of these studies were questioned and the classification reverted to the pre-1970 consensus of a single species containing two subspecies until the taxonomy could be resolved using modern techniques such as molecular sequencing. Thus, at present, there are two subspecies recognized in the genus Platanista, Platanista minor (the Indus dolphin) and Platanista gangetica (the Ganges River dolphin).[5]
Physical description
The Indus dolphin has the long, pointed nose characteristic of all river dolphins. The teeth are visible in both the upper and lower jaws even when the mouth is closed. The teeth of young animals are almost an inch long, thin and curved; however, as animals age the teeth undergo considerable changes and in mature adults become square, bony, flat disks. The snout thickens towards its end. The species does not have a crystalline eye lens, rendering it effectively blind, although it may still be able to detect the intensity and direction of light. Navigation and hunting are carried out using echolocation. The body is a brownish colour and stocky at the middle. The species has only a small triangular lump in the place of a dorsal fin. The flippers and tail are thin and large in relation to the body size, which is about 2-2.2 metres in males and 2.4-2.6 m in females. The oldest recorded animal was a 28 year old male 199 centimetres in length.[6] Mature adult females are larger than males. Sexual dimorphism is expressed after females reach about 150 cm; the female rostrum continues to grow after the male rostrum stops growing, eventually reaching approximately 20 cm longer. Calves have been observed between January and May and do not appear to stay with the mother for more than a few months. Gestation is thought to be approximately 9–10 months.
The species feeds on a variety of shrimp and fish, including carp and catfish. Dolphins are usually encountered on their own or in loose aggregations; they do not form tight, obviously interacting groups.
Human interaction
The Indus river dolphin has been very adversely affected by human use of the river systems in the sub-continent. Entanglement in fishing nets can cause significant damage to local population numbers. Some individuals are still taken each year and their oil and meat used as a liniment, as an aphrodisiac and as bait for catfish. Irrigation has lowered water levels throughout their ranges. Poisoning of the water supply from industrial and agricultural chemicals may have also contributed to population decline. Perhaps the most significant issue is the building of dozens of dams along many rivers, causing the segregation of populations and a narrowed gene pool in which dolphins can breed. There are currently three sub-populations of Indus Dolphins considered capable of long-term survival if protected.[7]
The Indus river dolphin is listed by the IUCN as endangered on their Red List of Threatened Species [1] and also by the U.S. government National Marine Fisheries Service under the U.S. Endangered Species Act.
See also
References
- ^ a b Template:IUCN2008 Database entry includes justification for why this species is endangered
- ^ "Susu, the blind purpoise ... in the Ganges River, blind porpoise of Asia". The New Book of Knowledge, Grolier Incorporated. 1977., page 451 [letter A] and page 568 [letter S].
- ^ Kinze, C.C. (2000). "Rehabilitation of Platanista gangetica (Lebeck, 1801) as the valid scientific name of the Ganges dolphin". Zoologische Mededelingen Leiden. 74. [1]: 193–203.
{{cite journal}}: External link in|publisher= - ^ Pilleri, G., G. Marcuzzi and O. Pilleri (1982). "Speciation in the Platanistoidea, systematic, zoogeographical and ecological observations on recent species". Investigations on Cetacea. 14: 15–46.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Rice, DW (1998). Marine mammals of the world: Systematics and distribution. Society for Marine Mammalogy. ISBN 978-1891276033.
- ^ Kasuya, T., 1972. Some information on the growth of the Ganges dolphin with a comment on the Indus dolphin. Sci. Rep. Whales Res. Inst., 24: 87-108
- ^ Braulik, G. T. (2006). "Status assessment of the Indus River dolphin, Platanista gangetica minor, March–April 2001". Biological Conservation. 129: 579–590. doi:10.1016/j.biocon.2005.11.026.
- General references
- Randall R. Reeves; Brent S. Stewart; Phillip J. Clapham; James A. Powell (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf, Inc. ISBN 0-375-41141-0.
External links
- US National Marine Fisheries Service Indus River Dolphin web page
- Video of 10 Dolphin Sitings by Humbal
- ARKive - images and movies of the ganges river dolphin (Platanista gangetica)
- Convention on Migratory Species page on the Ganges River Dolphin
- Walker's Mammals of the World Online - Ganges River Dolphin
- World Wide Fund for Nature (WWF) - species profile for the Ganges River dolphin
- WDCS: dolphins and whales of west indi ocean