Platanista gangetica

Common Names:

Ganges river dolphin, blind dolphin, Ganges dolphin, Ganges susu, Gangetic dolphin, Hihu, Bhagirath

Taxonomy:

Kingdom :    Animalia
Phylum :    Chordata
Class  :    Mammalia
Order :    Cetartiodactyla
Family :    Platanistidae
Genus :    Platanista
Species :    P. gangetica (Lebeck, 1801)

Conservation status:

IUCN :    Endangered
IWPA :    Schedule I
CITES :    Appendix I
U.S ESA  :    Not listed

Distribution:

P. gangetica historically distributed in major river systems (Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu) of India, Nepal and Bangladesh between longitudes 77o E and 89o E. Rocky barriers, dams, barrages, shallow water, and fast currents prevented upstream movement of the species in India and Nepal. But currently, the species restricted to disjunct stretches in India’s Ganga-Brahmaputra-Barak river system, Nepal’s Karnali, Sapta Koshi and Narayani river systems, and Bangladesh’s Meghna, Karnaphuli and Sangu river systems. According to the recent study in the Ganga River Basin, the species recorded from the main stream of Ganga River followed by the tributaries, Ghaghra, Kosi, Gandak, Chambal, Rupnarayan, and Yamuna.

Distribution Map of Ganges River Dolphin (Source: iucnredlist.org/species/41756/50383346 )

Characteristics, Habitat and Behaviour:

A long thin snout, rounded belly, stocky body and large flippers are characteristics of the Gangetic 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 Gangetic 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 Gangetic 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:

Das, G. C., Sharma, S. P., Ali, S. Z., Gawan, S., Usmani, A. A., Sarkar, A., ... & Hussain, S. A. (2022). Prioritising river stretches using multi-modelling habitat suitability of Gangetic dolphin (Platanista gangetica) as a flagship species for aquatic biodiversity conservation in the Ganga River Basin, India. Ecological Indicators, 145, 109680.

Kelkar, N., Smith, B.D., Alom, M.Z., Dey, S., Paudel, S. & Braulik, G.T. (2022). Platanista gangetica. The IUCN Red List of Threatened Species 2022: e.T41756A50383346. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T41756A50383346.en. Accessed on 19 May 2023.

http://https://egazette.nic.in/WriteReadData/2022/241252.pdf

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