Biology Reference
In-Depth Information
Distribution of the Susu: Historical and Current
Historical Distribution
The water-hog (P.
khuk-abi
,
Platanista gangetica
, the porpoise) is in all Hindustan rivers
(quoted in the ‗Babur Nama'
,
a book written by Babur in the 15
th
Century, the first ruler of
the Mughal Dynasty in India). The topic contains a miniature painting depicting the Ganges
River dolphin. By stating ―all Hindustan rivers‖ Babur probably meant all the rivers of North
India as he had widely traveled mainly in the Indo-Gangetic plains of northern India.
Anderson (1879) recorded its distribution in the Ganges over an area comprised between 77
0
E
and 89
0
E Longitude; in the Brahmaputra it occurred throughout the entire main river, as far
eastwards as longitude 95
0
by latitude 27
0
30' north. He also reported that even in the month of
May, when the Ganges was very low, it extended up the Yamuna as far as Delhi. Anderson
emphasized that the upstream range of this dolphin was apparently only limited by
insufficiency of water and by rocky barriers. The last record of susu in Yamuna at Delhi was
in 1967, when a dead dolphin caught in a fishing net was brought to the Delhi Zoo (personal
communication Dr. K. S. Sankhla, the then Director, Delhi Zoo).
Current Distribution
The Ganges River dolphins live mainly in the rivers originating from the Himalayas and
some tributaries of the Ganges originating in the central India below an elevation of about
250 m. In the Ganges valley it ranges into most of the large tributaries: the Yamuna, Son,
Sind, Chambal, Ramganga, Gomti, Ghaghara, Rapti, Gandak, Kosi, etc besides the main
channel of the Ganges. In the Brahmaputra valley it also ranges into many of the major
tributaries: the Tista, Adadhar, Champamat, Manas, Bhareli, Subhansiri, Dihang, Dibang,
Lohit, Disang, Dikho and Kulsi rivers. Downstream it ranges through most of the rivers in
Bangladesh, as far as the tidal limits at the mouth of the Ganges. They are also reported to be
within the Fenny, Karnaphuli, and Sangu rivers to the southeast of the mouths of the Ganges
(Rice, 1998). The uppermost distribution is said to be restricted only by the lack of water and
rocky barriers (Reyes, 1991). Relatively high population densities (approx.125) have been
observed in the 60 km stretch of the Ganga, the Vikramshila Gangetic Dolphin Sanctuary, in
the state of Bihar in India. There is a small (perhaps 20 individuals) but potentially viable
population in the Karnali River, the largest river system in Nepal, now isolated by the Girija
Barrage located about 25 km downstream of the Nepal-India border (Smith et al., 1994).
During a continuous survey in the Ganga from Haridwar downward, in the month of
December 1996 when water was low, we could not find susu in the 100 km stretch of the
river between Haridwar and Middle Ganga Barrage at Bijnor. However, in September 1994
one susu was sighted in the Ganges at Nangal about 30-40 km downstream Haridwar (Pers.
Comm. Raju Kumar). During a status survey conducted in 1978, the susu were found most
abundant from Munger to Sahibganj in Bihar; common up to the Farakka Barrage towards the
east and up to Varanasi or slightly more westwards (Gupta, 1986). Gangetic dolphins were
fairly common in tidal waters but never entered the sea (Agrawal, 1991).
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