Indian Humpback Dolphin

The Indian Ocean humpback dolphin is a medium-sized dolphin of coastal waters from southern Africa to western Indochina, including East Africa, the Middle East and India. It was once lumped with the Indo-Pacific humpback dolphin, but a 2014 study showed them to be separate species. It measures 2 to 2.8 m and weighs 150 to 200 kg. It has a fatty hump on the back, which distinguishes it from the Indo-Pacific species, and is generally dark grey, with young dolphins darker above than below. It surfaces at a 30 to 45 degree angle, sometimes showing the whole head, before arching its back (Wikipedia, general species account).

Most animals stay in water shallower than 20 m. It lives in groups averaging about a dozen, although group size varies widely and some exceed 100. The diet is mostly sciaenid fishes, cephalopods and crustaceans. Its shallow coastal habitat exposes it to pollution, by-catch, vessel strikes and noise. The 2012 national list has it as Near Threatened under the name Indo-Pacific humpback dolphin (Sousa chinensis) (Sri Lanka National Red List 2012).