CHAPTER 1
IN T R O D U C T IO N
1.1. General:
The order Cetacea includes aquatic mammals of c 80 different species ranging
from the largest creature on earth, the blue whale to the killer whale, the most
cosmopolitan mammal.
They have evolved from terrestrial ancestors but have
adapted themselves to a totally aquatic existence.
River cetaceans are among the world’s most threat
pfthe river systems of Southern Asia. (Rj
f
~ ~ / v
reported to range upstream from the estuarine zone to rocky barriers and shallow
reaches in headwater streams
Populations of river cetaceans have declined
dramatically in recent years and much of their spatial ranges have been lost
River
dolphins arejjarticularly vulnerable to(the activities'^ human interference because of
the restricted nature of their habitat.
Till date there have been five species o f river
dolphins, o f which one species occurs in marine waters
(i) Inia geoffrensis,
(Figure 1).
commonly known as boto or Amazon river dolphin
It is found in the Amazon and Orinoco basins
of boto is c 332 ±55 (Perrin and Brownell, 1989)
The present population
The populations are highly
2
vulnerable because of several threats to the Amazon/ Orinoco aquatic ecosystems
These threats include interactions with fisheries, hydroelectric development,
deforestation and pollution from agriculture, industiy and mining
(ii) Lipotes vexillifer, commonly known as baiji or Chinese river dolphin is
found only in the Yangtze river in the Peoples Republic o f China (Figure 1 )
It is
the rarest of all river dolphins and classified by the IUCN as Critically endangered
(Smith, 1999). Only a few tens o f baiji are thought to exist(as/d^now. Conservation
efforts^jattem pting to translocate animals from the main river into a single semi­
natural reserve, a blocked-off side channel^have not proved successful for the baiji.
(in) Pontoporia blainvillei, commonly known as la plata dolphin is the smallest
of the Platanistoid dolphin and only one that occurs in marine waters
It is known
by the local name o f Franciscanal Toninha/ Cachimbo. It inhabits the coastal waters
of Brazil, Uruguay and Argentina. The status of this species is uncertain as there are
no estimates o f abundance ( Perrin and Brownell, 1989)
The principal threat is
incidental catch ingill nets, which has existed for at least the last forty years
(iv) Platanista minor, the Indus river dolphin is closely related to P. gangetica.
It is locally known as buhlan
It is restricted to Pakistan only The buhlan is the
second- most endangered river dolphin
The buhlan survives as a metapopulation of
a few hundred individuals, c 500 (Khan and Niazi, 1989)
Large portions of buhlan
habitat were lost as the Indus river was transformed by extensive water development
3
from a dynamic alluvial system into an artificially-controlled and sub-divided
waterway.
(v) Platanista gangetica, (Q) commonly known as the Ganges River Dolphin
(GRD).( (It)is one of two river dolphins found in the Indian sub-continent, the other is*
AP. minor as described'to heretofore^ GRD inhabits the main channel of the Ganges,
—
—
........
the Brahmaputra, the Meghna and Karnaphuli and Karnali circumventing into the
countries o f India, Bangladesh and Nepal (Mohan, 1989; Perrin et al, 1989). GRD is
identified
in
Assam through various
local
names
These
are
hihufheho
(Assamese), patikari ( Missing plain tribe), shushuk ( Bengalee), sounch (Beharis of
upper Assam).
Mohan (1989b) reported that GRD were found in abundance
formerly but its population has now dwindled to c 3000
GRD faces a series of
threats including pollution, dams, mining and both directed and incidental catch.
The population trend for this species is gravely approaching towards a shrinking
range as GRD are fast being eliminated from smaller tributaries and even the
declining populations are killed in fishing gears and directed hunts as they compete
unsuccessfully with humans for shrinking waters and prey resources
(Smith, 1999).
1.2. GRD status:
Platanista gangetica ( Roxburgh, 1801) is classified in the Red Data Book
(Klinowska, 1991) and in India is protected under the' Indian Wildlife(Protection)
Act, 1972. The IUCN recently changed the species status from vulnerable to
«
4
endangered (Smith, 1999).
It belongs to the Family Platanistidae, Suborder
Delphinoidea; order- Cetacea of class: Mammalia
The GRD population in the “ Ganges delta zone” is estimated to be about 3000There may be c 500 to 750 in the entire Ganges river zone and
3500 (Jones, 1982).
the Meghna river may support about 750 dolphins
(unpublished data)
Singh and
Sharma (1985) found c 45 dolphins as resident population In Chambal river
(1976) guess estimatec
Haque
600-800 GRD for all of Bangladesh. Reeves et al (1992)
/
stated that there are around 3000-3500 GRD in total, with c 2000 in India, 1000 in
Bangladesh, 40-50 in Nepal and 20-30 in Bhutan. Mohan et al (1997) estimated c 268
GRD in the river Brahmaputra.
1.3. Morphological characteristics of the GRD: ( Figure 1 )
The head is clearly distinguishable from the body. There is a noticeable neck. The
single nostril or'(theblowhole is located on the top of the forehead, the melon that is
used for aerial respiration. The beak-like snout is long and narrow, biset with c 110
to 144 conical teeth
The melon rises abruptly and is rounded, giving the head an
almost birdlike appearance. The eyes are tiny and reportedly lack a lens. The melon
forms the principal site for echolocation, a special device present in GRD which is
s
used for foraging and to sense objectj^There is a low triangular hump in place o f a '
orsal. The paired breast flukes known as flippers are short and each has a
A-
5
broad fan-like appearance, c 22.5cm x 17.5 cm in size
Tail fluke is broad and has
two lobes. Length of tail fluke measures c 35cm. Genital and cloacal openings are
separate and are located on the ventral side o f the body with the former being situated
quite anteriorly to the latter. The GRD population is categorized into Calf, Juvenile,
Sub-adult and Adult stages. The salient distinguishing characteristics o f each stage
are as follows:
Calf: Newborn baby o f dolphin, the total body length ranging from 25-30cm.
tLcv&i - v£AAj3^reJi-.>4- v w
^
The body is slender with its^girthc 6-7cm5iffvertk^lline:
Its beak is straight and its
length varies from c 5-7 cm. (20% of the total body length)
The colour o f the
newborn calf is dark brown in general with lighter tinge ventrally.
Juvenile: Body length c >40 to <100cm. The beak is straight and its length
w
u
varies from 9-16cm, Slender body and girth is c 10-14 cm. Dorsal fin is distinct
Body colour is lead with darkish tinge dorsally and darker below. It is agile in nature
Sub-adult: Total length measures > 100—<150 cm.
Beak is straight and c 17-
22 cm in length. Curved beak is also found in some specimens.
v \
.
Dorsal fin is large.
il
Girth of the body ranges from 15-25 cm Body is dark-lead in colour
Adult: Size ranges from more than 150 cm in total length.
The beak length
»f
measures c 30-35 cm. The girth of the body varies from 30-35 cm. Body colour
varies from lead-black to greyish dorsally and pale-white ventrally
Dorsal fin is
FIGURE 1. SOME RIVER DOLPHINS ANDMORPHOLOGY OF
PLATANISTA GANGETICA (3 to 6); 1, IMA GEOFFRENSIS; 2, LIPOTES
VEXILLIFER
A, BEAK; B,BLOW HOLE; C, RECTAL & G, GENITAL OPENING,
E, EYE; F, FLIPPER; K, FLUKE
6
small and looks like a ridge only.
Older ones have some spots here and there on the
body.
1.4. Review of earlier works on the GRD:
Eschricht (1852) was probably the first worker to purport on the Gangetic
dolphin, Platanista gangetica .
Jerdon (1874) in his pioneering work on the
mammals o f India also referred to the dolphin inhabiting continental parts o f the
country.
Anderson (1879) published a detailed observation on the biology,
anatomy, behaviour and ecology o f the GRD from Assam and Bangladesh. Two
years later, Blanford (1891) published his treatise on the mammals o f British
India including the GRD.
After a gap of a hundred years since the works of
Anderson, Herald (1969) and Pilleri et al (1970) investigatedfOTKtfrc, GRD
behaviour in captivity. Thereafter, Pilleri (1970, 1980) made a detailed study on
the embryology, sonar mechanism and ecology including capture of a few
specimens from the river Brahmaputra.
Although the periods from 1971 to 1979 exhibited some investigations
(Pilleri, 1971, Kasuya, 1972; Kasuya and Haque, 1972; Hague, 1978) on the
GRD, it was in the periods from 1981 to the 1990s and thereafteriti.ll ddte; that an
upsurge o f investigations/on different aspects o f river dolphin from the Indian
subcontinent (was~found\
In this context reference may be made to Haque
7
et al (1977), Pelletier and Pelletier (1980), Haque 1982), Zhou (1982), Gupta
(1986), Perrin et al (1989), Mohan (1989a), Reeves and Brownell (1989),
Ridgway et al (1989), Shrestha (1989), Anon (1990), Klinowska (1991), Haque
(1992), Singh (1992), Smith (1990), Leatherwood eta l (1992), Smith eta l (1994),
Reeves and Leatherwood (1995) and Smith (1995) for their works on various
aspects of the Ganges river dolphin o f India, Pakistan, Bangladesh and Nepal
- /
9—
m
rGdod\ many workers have made important contributions (ph^the GRD census
/
^
___ /
in various/rivers (save the riv^>Bfahmaputra)ffom the Indian subcontinent notably
-------------- —
^
Haque (1976, 1978) from Kamaphuli river; Jones (1982), Khan and Niazi (1989),
Choudhury and Khalid (1989) from Indus river; Rao et al (1989), Hussain and
Choudhury (1992) from Chambal river and Shrestha (1989), Smith (1992), and
Smith et al (1994) from Kamali river.
Important contributions made by Pilleri(1971), Kasuya and Haque(1972),
Harrison(1972), Nath(1974), Butt(1977), Pelletier and Pelletier (1980), Singh and
Sharma(1985), Ralls (1989), Read (1990), Ahmed (1992), Choudhury and
Hussain (1992), Haque (1992) and Haque and Haque (1992) on GRD behaviour
from the rivers o f the Indian subcontinent are significant
On the ecology o f the rivers o f dolphin habitat Pilleri and Zbinden (1974)
and Mirza (1992) investigated/omthe Indus river system, Haque (1992)(from) the
8
A.
0—
k''-'
river o f Bangladesh, Sinha (1992)^om \the Ganges .wljMe Shrestha(1989) and
Smith (1992) rfrani the Karnali river, Nepal.
The need o(/conservation stra te g y ^ th e river dolphin has attracted attention
of various workers^notably of Perrin (1988, 1989), Mohan (1989b), Perrin and
Brownell (1989), Perrin et al (1989), Rao et al (1989), Shrestha (1989), Reeves
(1991), Leatherwood (1992), Sinha (1992), Shrestha (1992), and Smith (1992).
The anthropogenic stress factor on the GRD is paramount on the survival o f
this aquatic mammal. It was Pelletier and Pelletier (1980) who first reported
{ ^ q u ? ^ consumption o f dolphin meat by the inhabitants in some limited areas of
the Indian subcontinent. Thereafter, a good many workers like Ghosh (1991),
Hammond (1992), Mirza (1992) Mohan (1992a,b) and Prasad et al (1992) have
highlighted the impact of various anthropogenic stress on the GRD population
►x
1.5. Present work and its importance:
In sharp contrast to the aforementioned works on various aspects of the GRD
from the Indian subcontinent, scientific works on the GRD o f the Brahmaputra
river have been very limited and restricted to the works of Anderson (1879),
i
Pilleri (1970), Dey (1991), Dey et al (1992) and Mohan et al (1997) while work
on the ecology o f the GRD especially from
completely lacking.
the Brahmaputra drainages is
9
The present work, therefore, highlights the ecology o f the GRD in a
perennial tributary of the river Brahmaputra, the river Kulsi located in the
Kamrup district o f Assam, over ajperiod o f twenty-four months from January
1997 through December 1998. The treatise under report gets more prominence in
this field o f study due to the fact that the GRD of the river Kulsi are resident
inhabitants, occur throughout the year and this lotic territory is o f limited
dimensions suitable for an intensive empirical investigation All the salient
parameters within the purview o f the ecological studies o f the GRD have been
incorporated in the present study to get a coherent and comprehensive scenario in
the studied field hitherto remained unattempted.
SUNSET AT THE RIVER KULSI, THE ABODE OF PLATANISTA GANGETICA