Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 September 2018 | 10(10):
12350–12356
Alarming population status of the Grizzled Giant Squirrel Ratufa macroura (Mammalia: Rodentia: Sciuridae) in Chinnar Wildlife Sanctuary, the Western Ghats, India
Kiran Thomas
1 & Paingamadathil Ommer
Nameer 2
1,2 Centre for Wildlife Studies, College
of Forestry, Kerala Agricultural University, Thrissur,
Kerala 680656, India
1 kiranzthomas@gmail.com, 2 nameer.po@kau.in (corresponding
author)
doi: https://doi.org/10.11609/jott.3536.10.10.12350-12356 | ZooBank:
urn:lsid:zoobank.org:pub:6E8264BB-C1D8-4DA2-91C6-3B30D17DB7EB
Editor: Justus Joshua, Green Future Foundation, Tiruchirapalli, India. Date
of publication: 26 September 2018 (online & print)
Manuscript details: Ms
# 3536 | Received 03 June 2017 | Final received 01 July 2018 | Finally accepted
20 August 2018
Citation: Thomas, K. &
P.O. Nameer (2018). Alarming population status of the Grizzled
Giant Squirrel Ratufa macroura
(Mammalia: Rodentia: Sciuridae)
in Chinnar Wildlife Sanctuary, the Western Ghats, India. Journal of Threatened Taxa 10(10): 12350–12356; https://doi.org/10.11609/jott.3536.10.10.12350-12356
Copyright: © Thomas & Nameer 2018. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use of this article in any medium,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Funding: Kerala Agricultural
University.
Competing interests: The authors declare no competing interests.
Acknowledgements: The authors would like to thank the Chief Wildlife Warden, Kerala
State Forest department sanctioning the study (No. WL10-947/2013). The Warden Munnar Wildlife Division and the Asst. Wildlife Warden, CWS
provided the logistic support. We also thank the Kerala Agricultural University
for the financial support for the study and the Dean, College of Forestry, KAU for the
encouragement. Ponnusamy at Chinnar
WS and Akhil Das A, provided
excellent support in the field. The 2011 batch of B.Sc. Forestry students of
KAU helped us during the total population estimation of the GGS.
Abstract: This study was carried out to assess the population of Ratufa macroura in Chinnar Wildlife Sanctuary located in the Kerala part of
the southern Western Ghats. The
population density of Ratufa macroura was estimated to be 15.26 squirrels/km2. The total count method, however, gave the
population range between 11 to 14 squirrels.
The current population estimation is about 78–85 % lesser than the
previous population estimation of the Ratufa
macroura carried out in 1993 and 2007
respectively, which is quite alarming.
The following conservation recommendations are suggested for the
long-term conservation of R. macroura, which
include habitat restoration to maintain the canopy contiguity and regulation of
the pilgrimage and the tourism activities in and around the R. macroura habitat.
Urgent steps should also be taken to undertake studies on the genetics
of R. macroura.
It is also suggested that systematic and scientific monitoring of the
population of R. macroura be undertaken on a
regular basis.
Keywords: Hybridization, Idukki District, Kerala, line-transect method, PHVA, Ratufa indica,
riverine habitat, scrub jungle.
The
family Sciuridae consists of 285 species of squirrels
all over the world (Thorington et al. 2012), of which
the Indian subcontinent harbours 28 species in 12 genera (Johnsingh
& Nameer 2015; Nameer
et al. 2015). Among the four giant
arboreal squirrels belonging to the genus Ratufa,
three are found within Indian borders.
These are endemic to certain pockets of the Indian subcontinent, with
the Indian Giant Squirrel (Ratufa indica) distributed in peninsular India, the Malayan
Giant Squirrel Ratufa bicolor
in northeastern India and the Grizzled Giant Squirrel
Ratufa macroura
in peninsular India and Sri Lanka (Menon 2014; Borges
2015; Joshua & Johnsingh 2015). There are three subspecies of R. macroura. These
include R. m. dandolena, which occurs in
southern India and Sri Lanka while R. m. macroura
and R. m. melanochra are endemic to Sri Lanka
(Phillips 1981). Ratufa
macroura is endemic to
southern India (Kerala, Karnataka and Tamil Nadu) and Sri Lanka. In India it is known to survive in nine
severely fragmented locations, such as, the Grizzled Giant Squirrel Wildlife
Sanctuary, Srivilliputhur, Theni
Forest Division, Palani Hills, Anamalai
Tiger Reserve, Sirumalai, Thiruvannamalai
Forest Division, Hosur Forest Division and Cauvery
Wildlife Sanctuary (all in Tamil Nadu), the Cauvery basin in Karnataka and Chinnar Wildlife Sanctuary in Kerala (Babu
& Kalaimani 2014). The only known population of R. macroura in Kerala is in Chinnar
Wildlife Sanctuary (CWS). The habitat of
these giant squirrels in CWS is extremely unique and confined primarily to a
narrow stretch of riparian vegetation along the Pambar
and Chinnar rivers and their major tributaries (Ramachandran 1993).
Perhaps the only long-term ecological study on the
Grizzled Giant Squirrels at the Srivilliputtur
Grizzled Giant Squirrel Wildlife Sanctuary, Tamil Nadu were by Joshua
& Johnsingh (1994), Joshua et al. (2006), and
Raja & Joshua (2006).
The R. macroura population in India has been estimated to be
<500 mature individuals. It is also
observed that the R. macroura population has
been declining at a rate greater than 30% in the last 25 years due to habitat
loss and hunting (Molur et al. 2005; Joshua et al.
2008).
The previous
studies on the population estimation of R. macroura
at CWS were by Ramachandran
(1993) and Senthilkumar et al. (2007). The population data on a species with
restricted range distribution is very crucial in conservation prioritisation and there has not been any recent population
estimation carried out on the R. macroura in
CWS, and hence the present study was undertaken.
Materials and Methods
Study area
The study was conducted in Chinnar Wildlife Sanctuary, which is spread over an area of
90.44km². It is located between
10.25–10.350N and 77.08–77.260E in the Kerala part of the southern
Western Ghats, in Idukki District (Fig. 1). The terrain of Chinnar
is undulating with altitudes varying between 440m and 2,372m
. The major vegetation types
found here are, the southern tropical thorn forest (scrub jungle), southern dry
mixed deciduous forest (dry deciduous forest), southern moist mixed deciduous
forest (moist deciduous forest), tropical riparian fringing forest (riparian
forest), southern montane wet temperate forest (shola
forests) and southern montane wet grassland
(grasslands) (Champion & Seth 1968).
The dominant vegetation among these is the dry deciduous forest followed
by scrub jungle which is mainly found in the plains
and at lower altitude. The dry deciduous
and scrub jungle, together constitute about 70% of the total forest area in Chinnar. The
riparian fringing forests are linearly distributed and are confined to the
rivers Chinnar and Pambar,
and their tributaries. Shola forests
occupy a small fraction of the total area and are seen only in the higher
reaches of Chinnar, above an altitude of 1800m.
Ratufa macroura in CWS
is primarily seen only in the riverine forests along the Chinnar and Pambar rivers and
their tributaries. The riverine or
gallery forests are quite distinct and conspicuous among the surrounding scrub
jungle and dry deciduous forests of CWS.
The effective habitat for the R. macroura
at CWS is
estimated to be less than 2km2.
Methods
a. Line transect method: The line transect method by Buckland et al.
(2001, 2010) was
used in this study to estimate the population density of R. macroura. The
five transects were repeatedly walked once every month for 10 months (5x10=50)
thus fifty, 2-km transects were walked from April 2013 to May 2014. Each transect was walked by a team of three
persons. Each transect was walked in the
morning, between 06:00–10:00 hr and afternoon between
15:00–18.00 hr. Thus, a total of 200km
were walked during the study period.
When a squirrel was sighted we recorded the cluster size, which means
number of individuals at a time sighted, perpendicular distance, and azimuths
along the transect.
The data collected was analysed using DISTANCE
programme (version 6.2) (Buckland et al. 2004). We evaluated different models of detection
probability, viz. uniform, half-normal and hazard rate with three series
adjustment terms and used the minimum Akaike
information criteria (AIC) as the standard model selection procedure to select
the best model for estimating density.
Apart from the squirrel density, the encounter rate (squirrel
clusters/km) was also calculated.
b. Total count: The total count of
the R. macroura was carried out from seven
different blocks within CWS. Whenever a R.
macroura was sighted parameters like the number
of individuals, time of sighting, habitat and tree species on which the
squirrel was sighted were recorded. At
each of these locations we walked for 3 to 4h and the number of R. macroura was counted.
This was done simultaneously deploying a group of four people in each of
the seven blocks for two days in the study area on 22–23 March 2014.
c. Regeneration survey: A
regeneration survey was carried out at the study locations in the CWS, to find
out the regeneration of the vegetation in the riverine habitats. One hundred quadrats of 100m2 size
were taken, with 20 each at each of the five study locations. In each of these quadrats all plants ≥10cm
girth at breast height (1.37m) were enumerated, and the information such as
species of tree, height of the tree in meters and girth at breast height in centimetres were recorded (Pascal 1988).
Results
Population density estimation of R. macroura
using line transect method in Chinnar Wildlife
Sanctuary
The R. macroura
is a solitary animal and is seen in pairs or as a family party of three
individuals only during the breeding season.
A total of 85
detections of the R. macroura were made during
the study period, with an encounter rate of 0.21 squirrels per km (Table
1). The density of the R. macroura was estimated to be 15.26 squirrels/km2
(SE=2.96). The lower confidence
limit was 10.45 squirrels/km2 and the upper confidence limit was
22.30 squirrels/km2 (Table 1).
The effective strip width of the
riverine habitat used by the R. macroura was
calculated to be 0.04km using the DISTANCE (6.2) programme. The total length of the riverine habitat was
calculated using the software QGIS to be 40km.
Thus, the effective habitat for the R. macroura
at CWS is estimated to be only 1.6km2.
The total population
of R. macroura at CWS would be 24 squirrels
(15×1.6km2).
Total count of R. macroura in Chinnar Wildlife Sanctuary
The summary statistics of the total
count of R. macroura is presented in Table
2. A total of only 11 to 14 R. macroura could be counted during the total
count. The maximum number of R.
macroura was sighted in the Churulipetti
Block (8 numbers) followed by Alampetty Block (7).
Regeneration of riverine vegetation
The most preferred five plant
species by the R. macroura at Chinnar were Terminalia
arjuna, Mangifera
indica, Tamarindus indica, Ficus microcarpa
and Syzygium cumini
(Thomas 2014). The girth class
distribution of these five-plant species is given in Fig. 2. It is evident from Fig. 2 that the
regeneration of these tree species is extremely low in CWS.
Discussion
Population of R. macroura in Chinnar Wildlife
Sanctuary
The population
density of the R. macroura in CWS was found to
be 15.26 squirrels/km2. The
previous density estimations of R. macroura from
Chinnar were 18-23 squirrels/km2 (Ramachandran 1993) and 64 squirrels/km2 (Senthilkumar et al. 2007).
The population density estimated during the present study is lower than
the previous estimations.
The two census
methods that were used in the present study to estimate the population of the R.
macroura, indicate that the population of the
squirrels at Chinnar is between 14 and 24
individuals, using the total count method and line transect method,
respectively. The previous population
estimation of the R. macroura was 150 from CWS
(Ramachandran 1993), while
in another study it was estimated to be 107 squirrels (Senthilkumar
et al. 2007). Thus, there has been a
decline of about 78 to 85%, in the population of the R. macroura,
which is quite alarming. Baskaran et al. (2011), however, mentioned that the
population of R. macroura in the Anamalai landscape, including the CWS was 300
individuals. Joshua & Johnsigh (1994) estimated the population of R macroura to be between 82 to 115 individuals in the Alagarkoil Valley in the Srivilliputhur
Grizzled Giant Squirrel Wildlife Sanctuary, in Tamil Nadu, southern India. The Srivilliputhur
Grizzled Giant Squirrel Wildlife Sanctuary may be the stronghold for the
Grizzled Giant Squirrels in its entire range within the Western Ghats.
In one of the
previous population estimates, Senthilkumar et al.
(2007) gave a density figure of 64 squirrels/km2, which seems to be
an over estimation. Senthilkumar
et al. (2007) states that “the squirrel density was calculated as the total
number of squirrel sightings divided by the survey area” which is a crude
method of density estimation and is not as per the standard density estimation
protocol proposed by Buckland et al. (2004).
Conservation recommendations
The total population of the R. macroura (Image 1) in India is estimated to be fewer
than 500 mature individuals (Molur et al. 2005) and
60% of this population is believed to be found in Chinnar and adjoining Tamil Nadu. Thus, the present findings, which indicate a
drastic decline in the population of the R. macroura
is a matter of grave concern.
This small population of the R. macroura at CWS, is faced with the several
conservation challenges, such as increased predation risk (Thomas et al.
2017). This could be due to the opening
up of the of the canopy in the riverine habitat of Chinnar. Moreover,
the regeneration of the preferred food plant species of the R. macroura is extremely low. The poor regeneration is because of the heavy
grazing by the domestic cattle. Thus urgent steps should be initiated to
curtail the cattle grazing within the riverine habitat in Chinnar
WS. Additionally, habitat restoration programmes need
be initiated to ensure the regeneration of the most preferred five plant
species of the R. macroura such as Terminalia arjuna, Mangifera indica, Tamarindus indica, Ficus microcarpa and Syzygium cumini
urgently.
We saw several possible hybrid
individuals (Images 2 & 3) between R. macroura
and R. indica.
The hybrid individuals were primarily seen in Kootar,
Churulipetti and Chinnar-Marayur
border. There could be at least three to
four hybrids at Chinnar, which is about 17% of the
total population of Grizzled Giant Squirrel.
Detailed investigation on the status of hybrid individuals, reasons for
hybridization, and the genetics of the R. macroura
need to be urgently undertaken at Chinnar to find out
the genetic purity of this species.
Detailed taxonomic studies using molecular tools should be carried out
to ascertain the taxonomic status of the Indian population of the R. macroura. The
mix-up and hybridization between the R. macroura
and R. indica also should be monitored to find
out its effect on the long-term survival of the R. macroura. Importantly, a Population Habitat Viability
Analysis (PHVA) is also recommended for the long-term conservation of R. macroura. Joshua & Johnsingh
(1994), also recommend the need for systematic study on habitat quality,
feeding and breeding ecology of R. macroura if
the squirrel has to be conserved and saved from further population loss in its
range.
In addition to the above-mentioned
threats, anthropogenic disturbances in the form of pilgrimage at Churulipetti, tourism and road kills also pose conservation
challenges to the R. macroura. The disturbances from the pilgrims and
vandals in the riverine vegetation at Churulipetti
region should be regulated. This causes
considerable disturbance to the R. macroura,
as the riverine vegetation is the key habitat of these squirrels, and thus the
pilgrim’s entry to the riverine vegetation should be stopped. To prevent the road kills, regular crossing
points have to be identified and the animal should be provided with canopy
connectivity using the artificial structures like bamboo bridges across the
road. There are also some ill effects
due to the ecotourism ventures, for example, the log houses constructed on the
banks of the riverine habitat and the tree top huts, constructed on the top of
the trees in the riverine habitat, could be detrimental to the long-term
survival of the R. macroura.
It is also important to undertake
regular, systematic and scientific population monitoring of R. macroura on a regular basis, at least once a year to
understand the population fluctuation of this extremely small and dwindling
population of R. macroura at Chinnar Wildlife Sanctuary.
A population estimation of the R. macroura
in its entire range in southern India, also should be
carried out to ascertain their actual population in India.
Table 1. Density of Grizzled Giant
Squirrel estimated using line transect method and DISTANCE software in Chinnar Wildlife Sanctuary, Western Ghats
Parameters |
Values |
Effort (distance in km) |
200km |
Number of cluster (group) detections (n) |
85 |
Encounter rate (squirrel clusters/km) |
0.21 |
Model selected |
Hazard rate |
Minimum Akaike
Information Criteria |
457.07 |
Squirrel density / km2 ±
Standard Error |
15.26±2.96 |
Squirrel density 95% Confidence
Interval, lower limit-upper limit |
10.45±22.30 |
Table 2. The total count of Grizzled
Giant Squirrels at different study locations in Chinnar
Wildlife Sanctuary, Western Ghats
Name of the block/ date of the count |
Kootar |
Churulipetti |
Chambakkadu |
Athioda |
Alampetty |
Thoovanam |
Vannamthura |
Total |
22-03 2014 |
1 |
6 |
0 |
3 |
3 |
1 |
0 |
14 |
23-03-2014 |
1 |
2 |
4 |
0 |
0 |
1 |
3 |
11 |
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