Names: South Asian River Dolphin, Ganges River Dolphin, Indus River Dolphin, Blind River Dolphin, Ganges Susu
Appearance: Dark Gray/brownish-gray w/ pink belly
Weight: Up to 200lbs.
Size: 7 – 8.5ft.
Lifespan: Approx. 30 years
Family: Platanistidae
Genus: Platanista
Type: MammalFamily
Occasionally spotted in large groups of up to 10 individuals, South Asian River Dolphins are normally solitary animals – often spotted alone or in pairs. Very little is known about the social structure of the individuals in these groups.
Diet
Due to their long beaks, these animals are able to use them to probe the sediment along the bottom of rivers in search of clams, fish, and shrimp. Most feeding takes place in shallow areas, with the individual swimming on it’s side.
These dolphins have occasionally been observed feeding cooperatively. They generally dive anywhere between 30-90 seconds, though they are capable of diving for up to several minutes at a time. South Asian River Dolphins also have 26-39 pairs of teeth in each jaw that are useful for grasping prey. The teeth in the lower jaw are longer and curved, making them more fang-like.
Reproduction
South Asian River Dolphins typically reach sexual maturity at a length of around 5.5ft or more, and begin breeding between 6 – 10 years of age. Females give birth year-round to a single calf that may nurse for at least 1 year before being weaned.
Species
The Ganges and Indus populations of South Asian River Dolphins were long regarded as a single, identical species until 1971 when they were split into two species – Platanista gangetica and Platanista minor. However, the two taxa were reduced to subspecies of a single species in 1989. The two species are geographically separate and likely have not interbred for thousands of years.
Conservation Status
First listed as endangered in 2004 by the IUCN Red List of Endangered Species, the South Asian River Dolphin faces numerous threats, with as many as 843-1,171 individuals in the Indus subspecies when surveyed in 2001, and 1,200-1,800 individuals in the Ganges subspecies. However, the true number of the Ganges population is believed to be larger, as some potentially important areas have yet to be surveyed, and at least some of the counts and estimates were considered to be negatively biased.
Water development projects, pollutants, deliberate killings, as well as fishing gear all contribute to the deaths of these dolphins. Fishing gear is a severe problem throughout the range of this dolphin, particularly gillnets, mostly due to the overlap of prime fishing grounds and their preferred habitat. Fishermen in India and Bangladesh also have a strong incentive to kill these dolphins, as their oil is highly valued as a fish attractant. Tribal people in the upper Brahmaputra have been known to hunt these dolphins for their meat as well.
Eyesight
Unique to this species of cetacean is their pinhole-like eyes, rendering them almost completely blind. They lack a crystalline lens in their eyes, making them incapable of forming images on their retina. This is likely due to their living in murky waters, making acute eyesight unnecessary, though they are able to detect light.
Sources:
NOAA
IUCN Red List of Endangered Species
EDGE
MarineBio.org
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What is a South Asian River Dolphin?
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