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Ganges and Indus River Dolphin

The Ganges River Dolphin (Platanista gangetica gangetica) and Indus River Dolphin (Platanista gangetica minor) are two sub-species of freshwater or river dolphins found in India and Pakistan. From the 1970s they had commonly been regarded as separate species. The Ganges River Dolphin is primarily found in River Ganges and its tributaries in India while the Indus River Dolphin is found in the Indus river in Pakistan

Taxonomy

Until the 1970s the Indus and Ganges River Dolphins were regarded as a single species, first named by Roxburgh in 1801. However at that time it became clear that two populations, one centered on the Ganges River in India and the other in the Indus River in Pakistan had not interbred for many hundreds of years. Based on differences in skull structure, scientists declared the two populations as separate species. However Rice (1998), in his taxonomic classification of cetaceans that has become standard in the field, found that there were insufficient morphological differences to warrant distinction at the species level. Thus just one species is recognized in the genus Platanista and four true river dolphin species, each in its own family as well as genus.

Physical description

The Ganges and Indus River Dolphins are essentially identical in appearance. They have the long, pointed snout characteristic of all river dolphins. Both the upper and lower jaw sets of teeth are visible even when the mouth is closed. The snout thickens towards its end. The species does not have crystalline eye lens, rendering it effectively blind, although it may still be able to detect the intensity and direction of light. Navigation and the hunt for food are carried out using echolocation. The body is a brownish colour and stocky at the middle. The species has only a small triangular lump in the place of a dorsal fin. The flippers and tail are thin and large in relation to the body size, which are about 6.5 ft (2 m) in males and 8 ft (2.5 m) in females.

The species feeds on shrimp and small fish that prefer the waters close to the riverbed. Dolphins are usually encountered on their own but have traveled in groups more often historically, when populations were larger.

Population and distribution

The Ganges subspecies can be found in the Ganges River as well as the Brahmaputra, Meghna, Karnaphuli and Sangu river systems of India, Bangladesh, Nepal and Bhutan. Relatively high population densities have been observed near the Vikramshila Gangetic Dolphin Sanctuary in India and in the Sangu River in southern Bangladesh. Very few individuals (perhaps 20) are present in Nepal in the Karnali River. The total population is unknown, but certainly numbers in the hundreds and there are perhaps as many as a few thousand (but see “Human interaction” below)

The Indus subspecies resides primarily in the Indus River in Pakistan. In the nineteenth century its range was approximately five times greater than it is today, and included the Sutlej, Ravi, Chenab and Jhelum tributaries of the Indus. The highest population density occurs in Sind Province. However the National Government of Pakistan as “˜The National Marine Animal of Pakistan’ has officially declared them the other two symbols of Pakistan are Markhor (Official) Asiatic Lion (Unofficial).

A comprehensive population census of the Indus Dolphin that was completed in 2001 by WWF-Pakistan concluded that there are approximately 1,100 individuals alive today.

Ganges and Indus River Dolphin


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