Abundance
of food plant species and food habits of Rhinoceros unicornis Linn. in Pobitora Wildlife Sanctuary, Assam, India
Pradip Konwar 1, Malabika Kakati Saikia 2 & P.K. Saikia 3
1 Research Scholar, 2 Guest Faculty, 3 Reader, Department
of Zoology, Gauhati University, Guwahati-781 014,
Assam, India
Email: 3 saikiapk@rediffmail.com(corresponding author)
Date of publication (online): 26
September 2009
Date of publication (print): 26
September 2009
ISSN 0974-7907 (online) |
0974-7893 (print)
Editor: L.A.K. Singh
Manuscript details:
Ms # o1640
Received 05 September 2006
Final received 17 September 2007
Finally accepted 31 August 2009
Citation: Konwar, P., M.K. Saikia &
P.K. Saikia (2009). Abundance of
food plant species and food habits of Rhinoceros unicornis Linn. in PobitoraWildlife Sanctuary, Assam, India. Journal of Threatened Taxa1(9): 457-460.
Copyright: © Pradip Konwar, Malabika Kakati Saikia & P.K. Saikia 2009.
Creative Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium
for non-profit purposes, reproduction and distribution by providing adequate
credit to the authors and the source of publication.
Author Details: All
the authors specialized in animal ecology and wildlife biology. Pradip Konwar is a research scholar. His field of Interest is the wildlife biology
and conservation works of mammalian fauna in Assam.
Malabika Kakati Saikia teaches the specialized student of
animal ecology and wildlife biology. She has obtained her PhD degree on
butterfly diversity and ecology and specializes in
butterfly taxonomy, wildlife biology and biodiversity conservation.
P.K.Saikia is in charge of animal
ecology and wildlife biology special branch of the University. His field of
specialization is wildlife biology and wildlife conservation, ornithology and
biodiversity conservation including butterflies.
Author Contribution: All
three authors conducted field surveys at Pobitora WLS
but most of the surveys were done by P. Konwar; M.K. Saikia and P.K. Saikia wrote the
paper.
Acknowledgement: The authors are
grateful to the Chief Conservator of Forest, Government of Assam, for providing
permission to conduct field work at Pobitora Wildlife
Sanctuary; to the range officer, forest guards, mahout, and other forest
officials of PWS for their continuous support during the survey; and to the
surrounding villagers of PWS for their generosity with information during the
study.
Abstract: Food
habits and abundance of food plant species of Rhinoceros unicornisin Pobitora Wildlife Sanctuary were studied from
January 1999 through December 2001. Totally 32 numbers of Rhino food plants were identified, of which 15
were grasses, four shrubs, five aquatic hydrophytes and eight tree species (21
terrestrial and 11 aquatic). During the dry season, the Rhino feeds on almost
90% food items from Hemarthria compressa, Arundo donax, Phragmites karka, Cerex rubro-brumee etc. The other short grasses such as Cynodon dactylon, Andropogon ssp., Cenchrus ciliaris,Chrysopogon aciculatus and
tender and young shoots and twigs of Schelristechya fuesche, Saccharum spontaneum, Lagerstroemia flosreginae etc. are consumed in limited portions. The rhino consumes 11 cultivated crops and vegetables, viz., Ricinus communis, Oryza sativa, Solanum melongena, Lycopersicon esculentum, Solanum tuberosum, Brassica nigra, Luffa cylindrica,Luffa acutangula, Cucurbita moschata, Cucumis sativus andIpomoea batatas etc. Highest density of food plant species
observed in the study area were Cynodon dactylon (167.5/m2), Hemarthria compressa (73.75/m2), Vetiveria zizanioides (56/m2), Saccharum ravannae (51.5/m2), Pharagmites karka (50.75/m2), Leersia hexandra (46.75/m2), Brachiarea pseudointerrupta(40/m2) and Eichhornia crassipes (35/m2).
Keywords: Food
habit, food-plant status, Pobitora Wildlife
Sanctuary, Rhinoceros unicornis, Rhino.
Introduction
This study is on the food habits of the
Indian Rhinoceros Rhinoceros unicornis and the status of food plant species in Pobitora Wildlife Sanctuary (PWS), which holds the second
largest concentration of rhinos in Assam. As per 1999 census in Assam, there were about 1800 Rhinoceros unicornis out of which 1771 were distributed in three
protected areas, viz., Kaziranga National Park
(1649), Orang National Park (46), and Pobitora Wildlife Sanctuary (76). The rhinos have disappeared from the other
previously known sites in Assam.
Study
Area
Pobitora Wildlife
Sanctuary is located between 26012’-26015’N & 92002’-92005’E and 50km east
of Guwahati City on the south bank of the river
Brahmaputra within Morigoan District of Assam. Although PWS is the smallest (only 38.83km²),
it supports the highest density of rhinos in comparison to other areas of
Assam. The population census indicated
the presence of 54 rhinos in 1987, 56 in 1993, 58 in 1995 and 76 in 1999. The unit density of rhino in PWS is 4.62/km2,
whereas it is 3.60/km2 in Kaziranga National Park.
Pobitora Wildlife
Sanctuary was a grazing reserve for cattle before 1971. During that time a few rhinos strayed out of Lawkhowa and Orang wildlife
sanctuaries and gradually became resident. Two such grazing reserves comprising 38.83km² were declared as reserve
forests in 1971. In 1987, Pobitora was declared a wildlife sanctuary covering an area
of 16km². Presently the sanctuary is
surrounded by 20 villages, the farmlands of which are frequented by
rhinos. Although, a proper study of
habitat characteristics of PWS is yet to be done, the gross constituents are 80%
grassland, 18% woodland and only 1% wetland. According to Islam & Rahmani (2004), and Talukdar (1996), forestland covers only 2%, thatch with Albizia regeneration 8%, pure thatch 40%, thatch
with Phragmites karka and Arundo donaxetc. 20% and perennial waterlogged area 5% and swampy area 25.5%.
The climate is subtropical moist with
average maximum temperature 380C and minimum 90C, humidity ranges between 75%
and 95%. Rainfall occurs throughout the
year and annual rainfall is 3000mm. Maximum rainfall is during the months of July & August and the
driest month is January.
Methods
The
study was carried out from January 1999 to December 2001. Various methods were applied for collecting
the food habit data of R. unicornis and
distribution status and abundance of food plant species in PWS. The methods were: (A) Food habits of rhino by
direct observation and sampling of freshly deposited rhino dung-pile; and (B)
Status and abundance of food plants in the study site.
A.
Food habits of rhinos
(i) Natural
plants: To identify the food habits of rhinos in PWS, sites were monitored
extensively from elephant back and the data of food plant species of rhinos
were collected by the methods of Wallmo et al.
(1973), Neff (1974), and Riney (1982). Apart from direct sighting of food plant
species consumed, the browsing plant species were collected and identified in
the field and laboratory. Herbarium
sheets were prepared for reference and confirmation of identification of food
plant species with Kanjilal et al. (1934, 1936, 1938,
1939), Kanjilal (1940), and Kanjilal& Bor (1940).
(ii) Cultivated food plants: During the
survey, forest personnel, elephant mahouts and elderly persons from the village
were interviewed to understand the overall cultivated food plant species
consumed by the rhinos.
b.
Sampling rhino dung-pile: As the consumed food plant materials were not
completely digested this method was used to identify the food items, at least
up to the generic level. Fresh faecal matter of rhinos was collected from dung heaps,
washed with tap water, sieved and analysed as per
methods of Korschgen (1980), Holecheket al. (1982), and Cooperrider (1986).
B.
Status and abundance of Food plants
To estimate frequency, density and
abundance of food plant species, 50 stratified quadrates of size 1×1 m were
laid randomly in PWS. In all the
successive quadrates, each plant species was separately counted. Herbarium sheets for particular plants were
prepared only once even if they occurred in more than one quadrate. The required parameters were estimated with
the formulae used by Krebs (1985), Arumugam (1998),
and Southwood & Henderson (2000).
Results
Food
habits of rhino:
(a) Natural plants: The Great Indian
One-horned Rhinoceros consumed 32 naturally occurring plant species - 15
grasses, four shrubs, eight trees and five aquatic hydrophytes (Table 1). Out of these plants, 21 species were
terrestrial and 11 were aquatic. During
the dry season, about 90% of rhino food constituted Hemarthria compressa, Arundo donax, Phragmites karka, Cerex rubro-brumee etc. Other short grasses such as Cynodon dactylon, Andropogon ssp., Andropogon aciculatusand Cenchrus ciliaristender and young shoots and twigs of Saccharum spontaneum, Lagerstroemia flosreginae,etc. were consumed to a limited extent.
(b) Cultivated food items: Rhinos in Pobitora also consumed 11 different cultivated food plants
(Table 2), which grow in the periphery of the sanctuary during dry (winter) and
pre-monsoon seasons. Plants such as Ricinus communis, Oryza sativa, Solanum melongena, Lycopersicon esculentum, Solanum tuberosum, Cucumis sativus, Luffa acutangula, Luffa cylindrica, Cucurbita moschata, Brassica nigra and Ipomoea batataswere common in and around the boundary of the study area. The rhinos frequently raided the village
farmlands for food.
Status
of food plant species
Grass species recorded in high density
are Cynodon dactylon(167.5/m2), Hemarthria compressa(73.75/m2), Vetiveria zizanioides(56/m2), Saccharum ravannae(51.5/m2), Pharagmites karka(50.75/m2), Leersia hexandra(46.75/m2), Hymenachne pseudointerrupta(40/m2) and Water Hyacinth-Eichhornia crassipes (35/m2) (Table 3 & 4).
The Cynodon dactylon, Hemarthria compressa and Imperata cylindrica (sprouting stages) are the most
commonly used food plants of the rhinos at PWS. Entire portion of these plants above the ground level was consumed. Only small twigs and younger leaves of Vetiveria zizanioides, Saccharum ravannae, Phragmites karka, Imperata cylindrica, Pollinia ciliata, Saccharum spontaneum, Costus speciosus, Alpinia allughas, Ziziphus jujuba, Lagerstroemia flosreginae, Sachumannianthus dichotomus and Arundo donax were consumed.
According to the mahouts of Pobitora, during high-flood, rhinos consume the leaves of Ficus religiosa, Schelristechya fuesche, Syzygium fruticosum, Fleminigia ssp., Bambusa tulda and Thysanolaena agrostis. Rhinos swim out to eat grass tops sticking out of water. The top of these tall grasses and reeds are
not soft and not preferred under normal conditions. Rhinos and Water Buffaloes go under water and
eat the submerged grasses too. When they
surface they have mouthfuls of vegetation, chew and swallow above the water
level. Rhinos sometimes enter paddy
fields around the sanctuary and eat sprouting plants. Observations on feeding by night-raiding
rhinos were not made.
Discussion
Grasses play a major role in the food
requirements of the Indian Rhino to maintain its body weight of over
200kg. It needs approximately 150kg of
fodder per day (Dutta 1991). The Indian Rhinoceros grazes during early
morning, late afternoon and through the night. During heavy floods and dry season, rhinos consume Water Hyacinth (Eichhornia crassipes)
that occasionally causes purging. Rhinos
normally eat the tender sprouts of tree species and sprouting stages of tall
grasses such as Saccharum ravannae, Phragmites karka and Arundo donax. Our Observations
are similar to Dutta (1991). Food intake, about 90% comes from Hemarthria compressa, Arundo donax, Pharagmites karka, Cerex-rubro brumee during the dry season as these species occur in
the habitat in abundance at this time. Rhinos eat floating and creeping plants
species such as Ipomea aquatica,Enhydra fluctuans, Pistia stratiotes, Lemna perpusilla, Eichhornia crassipes, also,
which grow in marshy areas. Food habits
of rhinos differ locality-wise. Verbanacious shrubs are rejected as food in PWS, but in Kaziranga they eat the apical parts of verbanaciousshrub, Lippia geminata.
Although grasses constitute the favorite
fodder, the Indian Rhino is not averse to eating occasional delicacies like brinjal, capsicum and tomato; they avoid legumes like
peas. During the season when food is
plenty, rhinos do not eat bushy vegetation even if the saplings are invitingly
young and tender. Within the
surroundings of permanent forest camps inside a protected area, very often
discarded mature seeds attached to parts of vegetables such as gourd, pumpkin
etc. grow to new plants; such plants seem to be relished by the rhinos (Dutta 1991, Vigne & Martin
1994). During short periods of
high-flood, when there is food scarcity, rhinos generally congregate on high
land where limited number of natural plants other than grasses and herbs are
available. At this time the rhinos are
observed to eat the bark of trees, cane, leaves of Flemingia sp. and Albizzia sp. (Dutta 1991). During
the time of food scarcity, rhinos eat whatever vegetation is available, and
local forest guards report that Ficus religiosa, Zizyphus jujuba, Lagerstroemia flosreganaeare also eaten. The animal is known to
eat pulses, mustard plants, potatoes, gourd and other vegetables (Dutta 1991; Villagers pers. inter. 2001).
Monsoon flood regularly affects the
distribution pattern of rhino food-plant species in the sanctuary every year
(Forest Department Officials pers. comm. 2001). The other major problem of the rhinos at Pobitorais the invasion of grasslands by woodland species like Albizia procera. This serious threat needs to be controlled by uprooting the exotic alien
species. Presently, poaching and
encroaching are other major problems adding to scarcity of food plant species.
Conservation
problems and recommendation
1. Grazing by 2500-3000 cattle every day
is one of the major problems in PWS. This drives 20-25 rhinos every night to raid croplands as far as 7km
away in the adjacent villages.
2. Illegal collection of thatch grasses,
firewood and fishing by people throughout the year.
3. Entire area gets inundated by
high-flood during the monsoon and consequent silt deposit. The swamp areas and ‘beels’
are gradually becoming shallow. A few
highland platforms need to be created to protect the rhino population during
flood.
In view of the incremental rise in rhino
population density, it may become necessary to increase the cover area of PWS,
where the highest rhino density in relation to total area is noted. Regular conflicts between the immigrant
ethnic groups and forest officials, have to be
resolved in the interest of rhino conservation, by joint efforts of people and
the government.
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