Common Name: Indo-Pacific humpback dolphin
Size comparison against an average human
Pacific Humpback Dolphin (Chinese White Dolphin) range
Indian Humpback Dolphin range
Atlantic Humpback Dolphin range
Humpback dolphins (Sousa sp.): Two genetic variations of humpback dolphins occur along the Indian coastline,the Indian Ocean humpback dolphin (Sousa plumbea) along the west coast and the Indo Pacific humpback dolphin (Sousa chinensis) by the east coast. As genetic studies provide newer results this might change further. We shall keep you updated!
The Indo Pacific humpback dolphin is a large cetacean with a slender beak and a slight melon on the forehead. It has rounded flippers. The small but prominent dorsal fin is placed on a small hump in the middle of the back. This platform for the fin is not as distinctive in the chinensis as it is in plumbea, and is almost absent in the animals in the South China Sea. There are marked keels above and below the tailstock. 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 east India are light grey with predominantly pink pigmentation on the skin surface. 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.
Indo-Pacific humpback dolphin (Sousa chinensis) from Orissa, east India, showing a small fin on a reduced hump and loss of pigmentation in adults. A robust body with pronounced beak, is a common coastal species in India. @ Dipani Sutaria
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.
Hump-backed Dolphin generally feeds on fish, molluscs and crustaceans.
Early Records from India: This species is common in the coastal waters of east India. It is frequently caught in fishermen's nets.
|[?]||Skull from Visakhapatnam in the British Museum, gifted by Sir Walter Elliot.||De Silva, 1987|
|[?]||Stranding at Waltair, Vizagapatam, reported by Blanford.||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|
|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|
|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|
|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|
|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|
|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|
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. However, individuals without conspicous hump could be confused with Indian Ocean humpback dolphin and 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. Pink pigmentation and light coloured body.
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.