Ganges River Dolphin


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Platanista gangetica

Common Names:

Ganges river dolphin, blind dolphin, Ganges dolphin, Ganges susu, Gangetic dolphin, hihu, side-swimming dolphin, South Asian River Dolphin

Taxonomy:

Ganges River Dolphin

Kingdom :    Animalia
Phylum :    Chordata
Class  :    Mammalia
Order :    Cetartiodactyla
Family :    Platanistidae
Genus :    Platanista
Species :    gangetica

Conservation status:

IUCN :    Endangered
IWPA :    Schedule I
CITES :    Appendix I
U.S ESA  :    Endangered

Distribution:

Two subspecies (P. gangetica gangetica and P. g. minor) occur in the Indus, Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of the South Asian subcontinent, from the deltas upstream till they are blocked by rocky barriers, shallow water, fast currents, dams or barrages (low, gated diversion dams). The three river systems are disjunct and, therefore, have their respective dolphin subpopulations. However, there may be an occasional demographic interaction between the latter two during the high-water season if the freshwater plumes of the two systems meet. There is further subpopulation separation within all three systems, much of it caused by physical barriers constructed within the last 100 years.

 IUCN)

Distribution Map of Ganges River Dolphin (Source: iucnredlist.org )

Characteristics, Habitat and Behaviour:

A long thin snout, rounded belly, stocky body and large flippers are characteristics of the Ganges river dolphin. The species has a slit similar to a blowhole on top of its head, which acts as a nostril. Females are larger than males and give birth once every two to three years to only one calf. The calves have chocolate brown skin at birth, while the adults have grey-brown smooth, hairless skin.

The Ganges river dolphins can only live in freshwater and are essentially blind. They hunt by emitting ultrasonic sounds waves that bounce off of fish and other prey. They are frequently found alone or in small groups; generally, a mother and calf travel together. The dolphin has the peculiarity of swimming on one side so that its flipper trails the muddy bottom. It is understood that this behaviour aids them in finding food. Being a mammal, the Ganges river dolphin cannot breathe in water and must surface every 30-120 seconds. Because of the sound it produces when breathing, the animal is popularly referred to as 'Susu'. Although not well studied, the movement of the Ganges river dolphin follows seasonal patterns. It is observed that animals travel upstream when the water level rises, and from there enter smaller streams.

Major Threats:

  • Unintentional killing through entanglement in fishing gear.
  • Poaching for dolphin oil, used as fish attractant and for medicinal purposes.
  • Habitat destruction due to development projects (e.g. water extraction and the construction of barrages, high dams and embankments), pollution (industrial waste and pesticides, municipal sewage discharge and noise from vessel traffic) and overexploitation of prey mainly due to the widespread use of non-selective fishing gear.
  • Fragmented populations created by dams and barrages have degraded downstream habitat and created impoundments with high sedimentation and altered assemblages of fish and invertebrate species.


References:

Smith, B.D., & Braulik, G.T. (2012). Platanista gangetica. The IUCN Red List of Threatened

Species 2012: e.T41758A17355810

http://www.iucnredlist.org/details/41758/0

http://wwf.panda.org/what_we_do/endangered_species/cetaceans/about/river_dolphins/ganges_river_dolphin/