Ganges River Dolphin

Platanista gangetica

FIELD MARKS:
dolphinlike
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average 2.5m
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small ridge for dorsal fin
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long, distinct beak
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Fresh water habitat

Note

The Ganges river dolphin is practically blind. The eye does not have a lens so is incapable of forming images on the retina. However, it can sense light levels. It is believed that the loss of sight in this river dolphin is related to its habitat; the water in which it lives is so muddy that vision is essentially useless.

Description

"All teeth and no eye". The Ganges river dolphin ranges from 2.3 to 2.6 meters in length. Females are larger than males. Color varies from lead-gray to black. The undersides are lighter in color, some almost pink. The rostrum is long and the forehead is steep and rises abruptly from the base of the snout. The dorsal fin is small, simple and ridge-like, and the ends of the pectoral fins are squared instead of tapered. The neck is visibly constricted and the blowhole is a simple longitudinal slit. They have 28 to 29 teeth on either side of the jaw.

Habitat

Live only in the muddy waters of the Ganges, Brahmaputra, Meghna, Karnaphuli, and Hoogly river systems.

Range

Found in India, Nepal, Bhutan, and Bangledesh in the Ganges, Brahmaputra, Meghna, Karnaphuli, and Hoogli river systems.

Food

They probe the mud in river bottoms with their long snout in search of shrimp and fish.

Comments

Young are born year-round, but most births occur between October and March. A significant birth peak takes place in December and January, at the beginning of the dry season, when water levels are low and food is concentrated and easier to catch. Gestation lasts eight to nine months. The young are weaned and venture off on their own before they are one year old. They reach sexual maturity in ten years. They have been known to show growth past the age of twenty-six.

Although schools of three to ten individuals have been reported in particular parts of river systems, these animals are not gregarious and spend most of their time feeding and travelling solitarily. These groups may occur for mating purposes.

They swim all day and all night and continually emit sounds. One study showed that 81% of the sounds are echolocation and 5% communication. When you live alone there usually isn't anyone to talk to.

Echolocation is used by the dolphins in foraging and it helps these animals to sense objects; they can detect a wire one millimeter in diameter.

The Ganges river dolphin is found only in fresh water and may migrate locally to tidal waters during the monsoon season. During the hot, dry season the species disappears from areas of river systems where temperature, salinity, and food limitations may cause conditions to be too severe.

Vulnerable. This animal is hunted both for its meat, which is eaten, and for its oil, which is used to fuel lamps. Other sources of threat include fishing nets, in which the river dolphin often becomes tangled when it migrates to tidal waters in the monsoon season; and dams, which prevent the river dolphin from making its local migrations and separate potential breeding populations of animals from one another.



Copyright 1999-2003 - All Rights Reserved, By Norma Ranieri (EMail:Dolphintailz@oocities.com)



Credits

Much of the information found here has been adapted from the following sources:

http://www.geobop.com/mammals/Cetacea/Platanistidae/, All rights reserved.

http://animaldiversity.ummz.umich.edu/accounts/platanista/p._gangetica.html, All rights reserved.

Macdonald, David. 1984. The Encyclopedia of Mammals. Facts on File Publications, New York, pp 178-179.

Nowak, Ronald M. and Paradiso, John L. 1983. Walker's Mammals of the World, Vol II, 4th edition. The Johns Hopkins University Press, Baltimore and London, p 360.

Prater, S.H. 1965. The Book of Indian Animals. Bombay Natural History Society, India, p 313-314.

Wilson, Don E. and Reeder, DeeAnn. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference. The Smithsonian Institution Press, Washington and London, p360.

http://www.cetacea.org/ganges.htm, All rights reserved.

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