Indo-Pacific humpbacked dolphin
| Indo-Pacific humpbacked dolphin[1] | |
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Scientific classification  |
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Delphinidae |
| Genus: | Sousa |
| Species: | S. chinensis |
| Binomial name | |
| Sousa chinensis (Osbeck, 1765)
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| Chinensis-type range | |
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| Plumbea-type range | |
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The Indo-Pacific humpbacked dolphin (Sousa chinensis) is a species of humpback dolphin that is found in coastal waters ranging from southern Africa in the west to northern Australia and southeast Asia to the east.[2] The Indo-Pacific humpback dolphin is regarded as near threatened by the International Union for Conservation of Nature (IUCN).[2]
Contents
Range and habitat
There are two varieties, regarded by some biologists as separate subspecies:
- Chinensis-type (Chinese white dolphin) is the eastern variety, found in Southeast Asia and northern Australia
- Plumbea-type is found in western variety, found along the eastern coast of Africa and the northern Indian Ocean along the southern coast of the Middle East through India.[2]
However, DNA testing has indicated that the Chinensis-type dolphins from Southeast Asia are more closely related to the Plumbea-type dolphins than they are to the Chinensis-type dolphins from Australia.[2]
The Indo-Pacific humpbacked dolphin is a coastal species, generally staying within a few miles of the shore and preferring water less than 20 metres (66 ft) deep.[3][4] Sometimes it enter rivers, but usually does not swim far upstream.[3]
Description
The Indo-Pacific humpbacked dolphin is a medium-sized dolphin that ranges in length from 2 to 2.8 metres (6.6 to 9.2 ft) and in weight from 150 to 200 kilograms (330 to 440 lb).[3] Plumbea-type dolphins have a fatty hump on the back, while Chinensis-type dolphins have a more prominent dorsal fin, but no hump.[3]
Different varieties have different coloration, although young dolphins are generally gray, with darker gray above than below.[4] Plumbea-type adults are generally dark gray.[4] Chinensis-type adults from Australia are generally light gray above and lighter, possibly with some spotting, below, and as the dolphins age the rostrum, melon and dorsal fin get lighter.[4] Chinensis-type adults from South China are generally white with dark spots on the sides, although the white portions appear to be pink because of blood flow beneath the skin.[4]
Indo-Pacific humpbacked dolphins can appear similar to conspecific Indo-Pacific bottlenose dolphins, but the bottlenose dolphins lack the hump of Plumbea-type humpbacked dolphins.[3] And all humpbacked dolphins have a distinctive motion when surfacing, in that it surfaces at a 30 to 45 degree angle with the rostrum, and sometimes the full head, showing before arching its back and sometimes showing its flukes.[3]
Life history
The Indo-Pacific humpbacked dolphin is most often found in schools of less than 10 dolphins.[4] It eats a wide variety of fish and, in some areas, cephalopods, but it rarely eats crustaceans.[2]
For the Hong Kong population, births mostly occur between January and August.[4] Newborn calves are about 1 metre (3.3 ft) long.[3] Females become sexual mature at about 10 years old.[4]
Interactions with other cetaceans
The Indo-Pacific humpbacked dolphin coexists over much of its range with the Indo-Pacific bottlenose dolphin, which also lives in coastal areas.[3][4] It has been known to associate with the Indo-Pacific bottlenose dolphin.[3][4] It sometimes forms mixed schools with the Indo-Pacific bottlenose dolphin, at times the Indo-Pacific bottlenose dolphin is aggressive towards the humpbacked dolphin, and is able to dominate the humpbacked dolphin.[4] The Indo-Pacific humpbacked dolphin has been occasionally observed associating with the snubfin dolphin and in these interactions the humpbacked dolphin tends to be the aggressor.[4] Interactions may also occur with the long-snouted spinner dolphin and the finless porpoise.[3]
Interactions with humans
The Indo-Pacific humpbacked dolphin has occasionally been kept in captivity.[4] Currently, Indo-Pacific humpacked dolphins perform at Underwater World, Singapore.[5] Dolphin watching trips to see these dolphins occur in Hong Kong and Australia.[6]
The Indo-Pacific humpbacked dolphin is listed as near threatened by the IUCN.[2][4] The Taiwan population is considered critically endangered.[4] The Indo-Pacific humpbacked dolphin sometimes gets caught in fishing nets.[4]
Conservation
China has launched the largest sanctuary in the world designed for this species on Taiwanese coasts. Dolphins are also protected in other areas such as Gulf of Kutch.[7]
References
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- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ Perrin F.W., Koch C.C., 2007. Wursig B., Thewissen G.M.J, Encyclopedia of Marine Mammals. pp609. Academic Press. retrieved on 13-05-2014
