Sousa chinensis

Common Name: Indo-Pacific Hump-Backed Dolphin

Humpback Dolphin
Humpback dolphins size.svg

Size comparison against an average human

Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Mammalia
Subclass Eutheria
Order Cetacea
Suborder Odontoceti
Family Delphinidae
Genus Sousa
Species

See text
Humpback Dolphin Cetacea range map

Pacific Humpback Dolphin (Chinese White Dolphin) range


Humpback Dolphin Cetacea range map Indian

Indian Humpback Dolphin range


Humpback Dolphin Cetacea range map Atlantic

Atlantic Humpback Dolphin range

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.

humpbackdolphin

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.

humpbackdolphin1

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.