Indo-Pacific humpbacked dolphin

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Indo-Pacific humpbacked dolphin[1]
Conservation status
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Sousa
Species: S. chinensis
Binomial name
Sousa chinensis
(Osbeck, 1765)
Chinensus-type range
Plumbea-type range

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]

Range and habitat[edit]

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[edit]

The Indo-Pacific humpbacked dolpin 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[edit]

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[edit]

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[edit]

Indo-Pacific humpbacked dolphin performing at Underwater World, Singapore

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 the 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]

References[edit]

  1. ^ Mead, J. G.; Brownell, R. L., Jr. (2005). "Order Cetacea". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 732. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ a b c d e f g Reeves, R.R., Dalebout, M.L., 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). "Sousa chinensis". IUCN Red List of Threatened Species. Version 2013.1. International Union for Conservation of Nature. Retrieved 10 October 2013. 
  3. ^ a b c d e f g h i j Carwardine, M. (1995). Whales, Dolphins and Porpoises: The Visual Guide to All the World's Cetaceans. DK Publishing. pp. 174–175. ISBN 1564586200. 
  4. ^ a b c d e f g h i j k l m n o p Wells, R. and Scott, M. (2002). "Humpback Dolphins". In Para, G.J. and Ross, G.J.B. Encyclopedia of Marine Mammals. Academic Press. pp. 576–581. ISBN 0-12-551340-2. 
  5. ^ "Underwater World Singapore and Dolphin Lagoon". Sentosa. Retrieved 2013-10-11. 
  6. ^ "Hong Kong Dolphin Watch". Hong Kong Dolphin Watch Limited. Retrieved 2013-10-11.