A new site record of the Grizzled Giant Squirrel Ratufa macroura (Pennant, 1769) in the Hosur forest division, Eastern
Ghats, India and its conservation significance
N.
Baskaran 1, K. Senthilkumar 2 & M. Saravanan 3
1,2,3 Asian Nature
Conservation Foundation, Innovation Centre 1st Floor, Indian
Institute of Science, Bengaluru, Karnataka 560012, India
Email: 1 baskar@ces.iisc.ernet.in(corresponding author), 2 ksenthilkumar@ces.iisc.ernet.in, 3 saravanan@ces.iisc.ernet.in
Date of
publication (online): 26 June 2011
Date of
publication (print): 26 June 2011
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: Hema
Somanathan
Manuscript details:
Ms # o2632
Received 20 November 2010
Final revised received 28 January 2011
Finally accepted 14 May 2011
Citation: Baskaran,
N., K. Senthilkumar & M. Saravanan (2011). A new site
record of the Grizzled Giant Squirrel Ratufa macroura (Pennant, 1769) in the Hosur forest
division, Eastern Ghats, India and its conservation significance. Journal
of Threatened Taxa 3(6): 1837–1841.
Copyright: © N.
Baskaran, K. Senthilkumar & M. Saravanan 2011. 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.
Acknowledgements:We are grateful to the Tamil Nadu Forest Department
for permitting this study and the Asian Nature Conservation Foundation (ANCF)
for funding. We also thank Mr. K.G. Avinash, GIS Expert, ANCFin helping us to produce the distribution maps.
Abstract: The Grizzled Giant Squirrel is endemic to
southern India and Sri Lanka. In
India it is distributed in isolated populations with less than 500 mature
individuals, restricted
mostly to patchy riverine habitats. We have recorded the presence of this species (minimum 14 individuals)
across eight locations in Hosur forest division along the Cauvery riverine
forest, north of earlier reported locations in the Eastern Ghats. The documentation of this species in
the study area adds to our understanding of its distribution. These squirrels are canopy dwellers, hence discontinuous forest restricts their
movement and dispersal. Measures
including stop auctioning Tamarindus indica fruits on
large scale for commercial purpose by Forest Department, restoration of
habitat, maintenance of canopy continuity, reducing anthropogenic pressure and
translocating squirrels from larger populations are suggested to enhance the
long-term survival of this habitat specialist, which is on the brink of local
extinction in the study area. We
also suggest a comprehensive population assessment of the species to reevaluate
its global status.
Keywords:Distribution, Eastern Ghats, Hosur forest division, Ratufa
macroura.
Grizzled Giant Squirrel Ratufa macroura (Image 1) is endemic to
India and Sri Lanka. It is
distributed in isolated populations with an estimated population of less than
500 mature individuals in India and with a contiguous distribution in Sri Lanka
(IUCN 2010). Habitat loss and
hunting continue to reduce its numbers significantly throughout most of its
ranges (Joshua & Johnsingh 1992, 1994; Molur et al. 2005). The population size of the Grizzled
Giant Squirrel has its number in India has declined by about 30% in the last 25
years (Molur et al. 2005) and is presently listed as Near Threatened in the
IUCN Red List (Joshua et al. 2008). Placed in Appendix II of CITES to regulate its international trade and
is also included under Schedule I (Part I) of the Indian Wildlife (Protection)
Act (1972). In India, the Grizzled
Giant Squirrel is patchily distributed in the Western and Eastern Ghats, with
larger populations found in the former. In the Western Ghats, there are two major populations each numbering 200–300
individuals in Periyar-Agasthyamalai and Anamalai landscapes. The Periyar-Agasthyamalai population
has around 200 individuals (Joshua 1992; Palraj et al. 1992; Palraj & Kasinathan 1993) and
is distributed in the Srivilliputhur Grizzled Giant Squirrel Sanctuary. The Anamalai population totals about
300 individuals (Joshua et al. 2008) and is spread across Chinnar Wildlife
Sanctuary, Kerala, (numbering about 150–200, Ramachandran 1993;
Senthilkumar et al. 2007), and Anamalai Tiger Reserve, Tamil Nadu (with no
estimated figures, Kumar et al. 2007). Besides, a few individuals have been reported from Palani Hills in the
Western Ghats (Davidar 1989; Sharma 1992). In the Eastern Ghats, a small population is reported from
Kanakapura forest division, in southern Karnataka (Karthikeyan et al. 1992;
Kumara & Singh 2006), which is considered as the northern-most population
(Kumara & Singh 2006).
The species is confined largely to
riverine habitats in the rain shadow areas of southern India, feeds primarily
on seeds of immature and mature fruits from trees and climbers, with a strong
preference for Tamarindus indica(Joshua 1992; Ellerman 1961). The R. macroura in southern India is sympatric with the
Indian Giant Squirrel Ratufa indica in
the Palani Hills and Azhagarkoil and Ayyanarkoil area of Srivilliputhur
Grizzled Giant Squirrel Sanctuary (Joshua 1992). Unlike the R. indica,
which has a wider distribution and larger population across central and
southern India (Ellerman 1961; Borges 1989; Ramachandran 1992), the
distribution of R. macroura is confined to the southern India (Joshua
1992), and their populations are small and patchy (Ellerman 1961). Any new information in the occurence or
distribution of the species is therefore crucial for its conservation.
Study
Area
The study was carried out as part of a
biodiversity survey of the vertebrate fauna in Hosur Forest Division and its
contiguous habitats in Dharmapuri forest division (11.750–12.690N
& 77.300–78.750E) from June 2009 to May 2010,
located in the Eastern Ghats. The
study area spreads over 1896km2 and is bordered by Cauvery Wildlife
Sanctuary (CWS) on the southern side, Ramnagara forest division on the western
side and is surrounded mostly by human settlements on the northern and eastern
sides. The area represents
tropical dry thorn, dry deciduous and mixed deciduous vegetations and a few
patches of lowland dry evergreen forest, a patch of high altitude (1395m
Guttirayan Hill)
montane evergreen forest and a large tract (65km) of riverine habitat along the
Cauvery River, which is the largest perennial river in southern India, flowing
between Karnataka and Tamil Nadu on the southern side of the study area. The area also has a few Hindu temples
(Madhesvaran and Dhabakuli Appan), situated along the Cauvery River that attract a large number of pilgrim every year.
Methods
A rapid questionnaire survey was
undertaken, in which the local community and forest department staff were shown
photographs of various species of mammals including the two species of giant
squirrels (R. indicaand R. macroura)
and a checklist of mammals was thus prepared. This was followed by a reconnaissance survey carried out on
foot in search of various species of mammals, including direct sightings of
giant squirrels and their signs (nest/drey) in the forested habitats of the
study area. These surveys provided
information on existence of R. macrouraand confirmed the absence of R. indica in
the study area. Based on the
reconnaissance survey findings, we divided the study area into three
categories, viz., areas with no distribution (with no direct sightings or
nest), areas of possible distribution (only with old nest) and areas of
confirmed distribution (direct sighting with new and old nests) of R. macroura. Subsequently, an intensive systematic survey was carried out on foot
during morning (0700–1000 hr) and evening (1500–1800 hr) for a
period of 2–7 days both in the areas of possible and confirmed distribution
for further affirmation of the presence of R. macroura and also to map the extent of
distribution in detail. From the
direct sightings of R. macrouraduring these surveys, the number of squirrels found in each
of the surveyed areas were estimated. Geo-coordinates collected using Global Position System (GPS)
for each squirrel sighted were incorporated into the study site map
using Geographical Information System and a distribution map was
prepared. The earlier reported
locations such as CWS and Kanakapura Forest Division, Anamalai Tiger Reserve,
Palani Hills, Chinnar WS and Srivilliputhur Grizzled Giant Squirrel WS were
obtained from published literature (Davidar 1989; Joshua 1992; Sharma 1992;
Karthikeyan et al. 1992; Kumara & Singh 2006; Senthilkumar et al. 2007) to
produce a comprehensive distribution map of the species in India.
Results
and Discussion
Intensive surveys over a year across the
entire habitat in Hosur forest division and its contiguous habitats in the
adjoining Dharmapuri forest division recorded the presence of R. macroura in the Hosur forest division along the
riparian habitat of Cauvery River. The present documentation is the first scientific report on the
existence of R. macroura in
the study area. Joshua (1992), who
surveyed Dharmapuri forests (the present study area) during Feb–May 1989
(based on potential sites of occurrence that he listed, from the 1920–30
specimen collection locations of the Bombay Natural History Society, and
inquiries with forest officials, and conservationists), reported the absence of
the R. macroura. Kumara & Singh (2006), who
documented the species in habitats further south-westof our study area (from Shivanasamudra Falls to Mekedatu on the Cauvery River
in Karnataka), considered the same as the northern-most population of the
species in its entire distribution range. This clearly indicates that the existence of this species on the Tamil
Nadu side in the Hosur forest division was unknown earlier. In total during this study, we recorded
a minimum of 14 individuals, in addition to 62 nests located at eight different
sites along the riverine patch of Cauvery (Image 2) in Hosur Forest
Division. The present record adds
to the completeness of the distribution of R. macroura with a new northern most extension in the
Eastern Ghats of India (Image 3). The distribution of R. macroura reported earlier along the
Cauvery River in Karnataka (Karthikeyan et al. 1992; Kumara & Singh 2006)
and by the present study along the same Cauvery River in Tamil Nadu, indicatethat these are probably parts of a larger contiguous population found in the
past and presently isolated due to lack of canopy contiguity.
Being a canopy dweller, the species
largely depends on the tree canopy contiguity for its movement, nesting and
breeding (Joshua 1992). All the
eight sites, where the squirrels were found, were reserved forests (Kestur,
Bilikal and Mallahalli), but they were isolated from each other due to
discontinuity in the canopy. The
maximum stretch of contiguous canopy was less than 120m in length and 25m wide,
thus limiting free movement of R. macrourabetween the isolated patches. These patches naturally lack canopy contiguity on the north-south axis
due to the change of riverine forest into tropical dry thorn forest on the
north and the Cauvery River on the south. Further, these patches are presently
restricted to the northern bank of the Cauvery over a length of 20km on the
upstream, out of 65km stretch of the riverbank within Hosur and Dharmapuri
forest divisions. Therefore, gaps
in canopy contiguity can pose a major threat to the long-term survival of the
few isolated individuals due to detrimental effects of restricted gene flow
through restricted movement and dispersal. In addition, disturbances from the
presence of cattle grazers, cattle pens (farm) and pilgrims can further
deteriorate the quality of the habitat for the squirrels due to overgrazing by
cattle, wood cutting and, forest fire.
Management
Recommendations
Although such small populations with
isolated individuals are neither demographically nor genetically viable, the
species is found more often in small numbers (Davidar 1989; Karthikeyan et al.
1992; Kumara & Singh 2006; Kumar et al. 2007), with restricted distribution
mostly to riverine habitats, which is generally patchy in nature. The riverine habitats along the Cauvery
River are potential sites for the species, and hence measures such as (a)
restoration of habitat and maintenance of canopy continuity (through
afforestation of preferred tree species like Tamarindus indica and Mangifera indica), (b) stop auctioning
the Tamarindus indicafruits on large scale for commercial purpose by Forest Department, (c) reducing
anthropogenic pressure along the riverine habitats (through strict management
action against the cattle pens that are along the gallery forest of Cauvery
River), and, (d) translocation of a few individuals of R. macroura (in consultation with experts on these
aspects regarding number of individuals and age-sex classes and in keeping with
the needs and guidelines suggested by the Reintroduction Specialist Group) from
larger populations to this habitat would not only enhance their long-term
survival, otherwise on the brink of local extinction, but will also ensure the
availability of the largest riverine habitats for this habitat specialist. The species lacks an updated
comprehensive database on the distribution and population status across its
ranges. Since the species perhaps
faces the threat of becoming extinct in India, it definitely deserves attention
of conservationists to reevaluate its global status. Unless the species receives immediate attention for its
protection and conservation, it will be a difficult task to save it from
extinction (Paulraj 1991).
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