Sousa chinensis
Common Name: Indo-Pacific Hump-Backed Dolphin
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See text Pacific Humpback Dolphin (Chinese White Dolphin) range 
Indian Humpback Dolphin range 
Atlantic Humpback Dolphin range |
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| Source: Wikipedia |
General Description: This is a large animal with a stout body. It has a long, slender beak, and a slight melon on the forehead. It has rounded flippers. The small but prominent dorsal fin is placed on a hump in the middle of the back. This platform for the fin is distinctive, but is not found on all animals outside the Indian region. There are marked keels above and below the tail stock. There is a distinct notch between the tail flukes, which are moderately concave along the rear edge.
The colour of the species is highly variable, but specimens off India are ‘solid lead grey’. Longitudinal blotches are found on the ventral side in larger specimens. The lower jaw may be cream coloured. Calves have a uniform pale cream colouration.
Size: Adults, Male Hump-backed Dolphins may be 3.2 m long, and females up to 2.5 m. They weigh up to 285 kg. Calves at birth, 90 cm long.
Appearance At Sea: Hump-backed Dolphins surface to breathe in a very distinctive way. The beak emerges from the water first, and then the melon and hump. As it breathes, the animal cruises with the beak just on the water surface. Sometimes the head is lifted clear of the water and the hump and fin are clearly visible then. Finally the dolphin rolls, its head going down and the hump emerging more, before sliding out of view.
The usual social unit consists of a group of 2-20 who move together in an orderly fashion.Small groups of Hump-backed Dolphins often associate with large groups of Bottlenose Dolphins.
This species is said to cooperate with Mauritanian fishermen in catching mullet. The men beat the water with a stick on seeing a school of these fish. This attracts Hump-backed Dolphins and other dolphins, which drive the fish towards shore and into the fishermen’s nets.
Hump-backed Dolphins can heave themselves over mudbanks to get from one channel of water to another.
Found In: The Indo-Pacific Hump-backed Dolphin prefers to feed close to shore and in tidal creeks. It may enter rivers and estuaries. It is usually found in sheltered coastal waters including mangrove swamps. It is said to be seen in shallow waters less than 20 m deep and rarely out of sight of land.
There have been reports that the Hump-backed Dolphin is a vegetarian, but it feeds only on fish, molluscs and crustaceans.
Records from India: This species is common in the coastal waters of India. It is frequently caught in fishermen's nets. There are many records of the Indo-Pacific Humpbacked Dolphin from the Indian coast, including the Andamans.
| Date | Details | Sources |
|---|---|---|
| [?] | Skull from Visakhapatnam in the British Museum, gifted by Sir Walter Elliot. | De Silva, 1987 |
| [?] | Stranding on the Malabar coast reported by Blanford. | De Silva, 1987 |
| [?] | Stranding at Alibag, Bombay reported by Blanford. | De Silva, 1987 |
| [?] | Stranding at Waltair, Vizagapatam, reported by Blanford. | De Silva, 1987 |
| 1827 | Two skulls collected from the Malabar coast by Dussumier. | De Silva, 1987 |
| [?] | Mounted specimen in the Museum d’Histoire Naturelle, Laboratoire d’Anatomie Comparee, France. | De Silva, 1987 |
| [?] | Two skulls in the Bombay Natural History Society | De Silva, 1987 |
| 1837 | Sightings off Malabar. | De Silva, 1987 |
| 18 September 1854 | Sightings off Visakhapatnam. | De Silva, 1987 |
| 1866 [?] | “Delphinus lentiginosus” described by Owen from Walter Elliot’s collections made on the East coast. | Jerdon, 1867 |
| [?] | One cast ashore near Dhanu, Tanna district. | Sinclair, 1895 |
| 31 March 1901 [?] | Young specimen “Sotalia fergusoni” measuring 1 m (3 feet 6 inches) cast ashore at Trivandrum beach. | Lydekker, 1904 |
| 1903 | “Sotalia lentiginosa” – an immature specimen obtained from Travancore. | Pillay, 1926 |
| August 1908 | “Sotalia lentiginosa” specimen measuring 2.15 m (7 feet, 2 inches) obtained from Travancore. | Pillay, 1926 |
| 16 December 1976 | One dolphin washed ashore on the coast of Devka, 20°25’N, 72°53’E, identified as Sotalia sp. | Joglekar et al., 1975 |
| 1976–1980 | Eleven animals caught in gillnets off Calicut coast. | Lal Mohan, 1985 |
| 2 September 1978 | Male 2.7 m long dolphin caught in gillnet off Calicut. | James & Lal Mohan, 1987 |
| 22 December 1980 | Four animals sighted at Calicut Harbour. | De Silva, 1987 |
| 12 February 1981 | One entangled in gillnet off Calicut. | Lal Mohan, 1983 |
| 15 September 1981 | Female with foetus landed at Calicut. | Lal Mohan, 1982 |
| April 1982 | Sightings northeast of the Andaman Islands. | De Silva, 1987 |
| January–March 1983 | Four specimens washed ashore at Gahirmatha Beach, Bhitarkanika Wildlife Sanctuary, Orissa | James et al., 1989 |
| July 1983–December 1986 | 5,245 kg of this dolphin landed at Fisheries Harbour, Cochin. | Jayaprakash et al., 1995 |
| January–March 1984 | Three specimens washed ashore at Gahirmatha Beach, Bhitarkanika Wildlife Sanctuary, Orissa. | James et al., 1989 |
| January–March 1985 | Two specimens washed ashore at Gahirmatha Beach, Bhitarkanika Wildlife Sanctuary, Orissa. | James et al., 1989 |
| 5 February 1985 | One washed ashore near Mandapam, Palk Bay. | Krishna Pillai & Kasinathan, 1988 |
| January–March 1987 | Four specimens washed ashore at Gahirmatha Beach, Bhitarkanika. | James et al., 1989 |
| 1987 [?] | Live specimen caught in gillnet off Calicut. | Anonymous, 1987b |
| 18 June 1990 | One female washed ashore at Mandapam Camp, Gulf of Mannar. | Krishna Pillai et al., 1991 |
| 24 January 1991 | Female specimen landed at Tuticorin. | Arumugam et al., 1992 |
| [?] | “A few specimens” reported from Porto Novo. | Kumaran & Subramanian, 1993 |
| 11 July 1993 | Eight dolphins stranded at Tuticorin Major Harbour. | Mohamad Kasim et al., 1994 |
| 1993 [?] | Two females and three males entangled in gillnets at Calicut coast. | Lal Mohan, 1995 |
| 16 February 1994 | Female with foetus caught in drift gillnet off Tuticorin. | Arumugam et al., 1995 |
| 15 September 1994 | Carcass at Mandapam Camp, Gulf of Mannar. | Lipton et al., 1995 |
| 15 September 1995 [1994?] | Putrefied carcass at Seeniappa Dharga, Gulf of Mannar. | Lipton et al., 1995 |
| September 1996 [?] | Twelve dolphins observed in 25 km of coast from Elathur to Quilandy river, Kerala. | Lal Mohan, 1996c |
This species is recorded from Pakistan, Sri Lanka, Djibouti, the Gulf of Oman, the Gulf of Aden, the Arabian Gulf and the Red Sea.
World Distribution: The Hump-backed Dolphin is widely distributed in the warm temperate and tropical waters of the Indian and the western Pacific Oceans.
Could Be Confused With: Hump-backed Dolphins are very easy to identify because of the characteristic hump and distinctive way of breathing. Humpless Hump-backed Dolphins could be confused with Bottlenose Dolphins as they have a similar body shape.
Diagnostic Features: At sea, prominent dorsal fin placed on hump in the middle of the back; long, slender beak.
Stranded Specimens: A dead adult can be easily identified by its hump and number of teeth. There may be 29 to 38 pairs of peg-like teeth in each jaw. Bottlenose Dolphins with which Hump-backed Dolphins are sometimes confused have not more than 26 teeth in each side of both jaws.