Non-volant small
mammals of the Western Ghats of Coorg District, southern India
Sanjay Molur 1 & Mewa Singh 2
1 Zoo Outreach Organisation, 9A Lal Bahadur Colony, Peelamedu,
Coimbatore, Tamil Nadu 641004, India
2 Department of Psychology, University of Mysore, Manasagangotri,
Mysuru, Karnataka, India
Email: 1 herpinvert@gmail.com; 2 msingh@psychology.uni-mysore.ac.in
Date of publication
(online): 26 December 2009
Date of publication (print): 26
December 2009
ISSN 0974-7907 (online) |
0974-7893 (print)
Editor: Giovanni Amori
Manuscript details:
Ms # o2330
Received 20 October 2009
Final received 05 December 2009
Finally accepted 07 December 2009
Citation: Molur, S. &
M. Singh (2009). Non-volant small mammals of the Western Ghats of Coorg
District, southern India. Journal of Threatened Taxa 1(12): 589-608.
Copyright: © Sanjay Molur
& Mewa Singh 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: Sanjay Molur is the Executive Director of ZOO
Trust and is involved in various conservation activities such as assessments,
legislation, policies at the national and international levels. Mewa Singh is Professor of Psychology and is
involved in research on primates and behaviours. He has several international publications on
mammalian taxa.
Author Contribution: SM designed and
conducted the field work as part of his PhD and wrote the paper. MS helped with the design and writing the paper.
Acknowledgments:SM
is grateful to Sally Walker, Honorary Director, Zoo Outreach Organisation and
all his colleagues in the organisation for supporting him throughout his part
time PhD work, putting in extra effort to allow him to work full time at the
office, and for providing traps for the study. SM is grateful to his wife Payal for accompanying him to the field as
his able field assistant throughout the four years of study. Thanks are to Mike Jordan for providing
equipments for the field work such as spring balance, ear tags, gloves, etc;
and to Rajesh Kumar John and Neelesh Dahanukar for their help and advice in
statistics and the use of the statistical packages. SM thanks all the people
who helped him in his study in Coorg, owners who provided him permissions and
supported his stay during the study. Special thanks to Mrs. Praphulla Venugopal and late Mr. Venugopal who
were the first to provide space for a field station in Coorg and support in
terms of food and shelter during the first year of study. Also thanks to Drs. Sujata and Anurag Goel
and their daughter Maya for their enthusiastic hospitality and support during
the last three years of field work. Thanks are also to WILD, CCINSA and RILSCINSA.
Abstract: A
study to understand diversity and changes in non-volant small mammal
composition in the Western Ghats of Coorg District, Karnataka was conducted
from April 2004 to April 2008. A total
of 11060 trap nights of sampling in various habitats such as forest fragments,
coffee and cardamom plantations, open areas including grasslands, agricultural
fields including paddy and ginger cultivations, bamboo and in and around human
habitations across the two vegetation zones of the district. Totally, 14 species of non-volant small mammals
were trapped as 412 unique individuals contributing to an overall trap success
of 3.8%. Rattus wroughtoni was
the most commonly caught taxon followed by Suncus murinus and S.
niger although S. murinus was trapped in 10 habitats followed by Mus
musculus in 9 of 11 habitats. The
abundance of small mammals was the highest in bamboo (12.1%) and in forest
fragments (7.2%); the plantations supported very low abundances (<
3.1%). Endemic mammals such as Rattus
satarae, Vandeleuria nilagirica, Platacanthomys lasiurus, Funambulus
tristriatus and Suncus niger were recorded in Coorg although P.
lasiurus and V. nilagirica were trapped in only one habitat
each. Changes in land use and rapid
decline in quality of habitat is pushing the endemics into local extinctions
while non-endemic commensals are displacing restricted endemics in disturbed
habitats. This study underlines the need
for more in-depth rapid assessments in the Western Ghats for the poorly
understood small mammals and the initiation of conservation programmes for
endemics.
Keywords: Diversity, Eulipotyphla, Muridae, Platacanthomyidae, Rodentia, Sciuridae, Soricidae,
Western Ghats.
For Figures, Images &
Tables – click here
Introduction
Volant and non-volant small mammals
constitute almost 75% (73%) of the world’s mammalian diversity with just the
non-volant small mammals contributing a little over 50% (52.5%) (Amori &
Gippoliti 2000; Wilson & Reeder 2005). The composition is very similar in South Asia (Molur et al. 2002; Molur
et al. 2005) and in the Western Ghats (Nameer et al. 2001). Their composition is usually not reflected in
biodiversity inventories due to the lack of specific methods required to understand
their diversity. Most instances of
documentation are sporadic and opportunistic. Shanker (2003) provides a comprehensive overview of the studies on
non-volant small mammals in India by various researchers.
The earliest inventory of small mammals
in India was by the Bombay Natural History Society’s Mammal Survey of India
project, which included all groups, in the early 20th century. The Mammal Survey of India was a pioneering
effort in documenting the mammalian fauna of the Indian Subcontinent including
India, Bhutan, Myanmar and Sri Lanka. A
total of 30 locations were surveyed throughout the subcontinent and as many
reports were published. Ryley (1913)
published the Coorg report (No. 11) based predominantly on the collections and
field notes by G.C. Shortridge, who worked extensively for two months,
December-January of 1912-13 in the small district of Western Ghats.
Much of Coorg’s natural habitats lie
restricted to the western and northern boundaries of the district, while much
of the central, eastern and southern zones have been converted to plantations
or agriculture. Barring Nagarahole
National Park, which lies to the southeastern part of the district adjacent to
Wyanad Wildlife Sanctuary of Kerala in the south, majority of Coorg’s protected
areas and reserve forests lie in the western and northern zones. Brahmagiri, Talakaveri and Pushpagiri
wildlife sanctuaries along with many reserve forests interspersed between the
protected areas form an extensive length of relatively undisturbed medium elevation
evergreen forests.
The Nilgiri Biosphere Reserve extends
from the Nagarahole National Park in the west to the Bandipur and Mudumalai
National Parks in the east across the three states of Karnataka, Kerala and
Tamil Nadu. The Brahmagiri Wildlife Sanctuary
in the southwestern part of Coorg District is separated from the Nilgiris by a
mere 30km, with towns such as Kutta and Srimangala occurring in the intervening
area. The division being artificial,
species occur commonly in the Nilgiri Biosphere Reserve and in the adjoining
parts of Coorg.
In the last decade or two, there has
been an increased focus on the ecological aspects of small mammals, which is
reflected by several studies in southern India. All of these studies concentrated on small mammal composition and
ecology in the forested areas of the Western Ghats (Chandrashekhar 1989,
Chandrashekar-Rao & Sunquist 1996 in the Anamalais; Venkataraman 1997,
Venkataraman et al. 2005 in Mudumalai Wildlife Sanctuary; Prabhakar 1998 in
Anamalai hills; Umapathy & Kumar 2000 in Anamalai hills; Shanker 1998,
2000a, 2000b, Shanker & Sukumar 1998, 1999, Shanker 2003 in upper Nilgiris;
Mudappa et al. 2001 and Kumar et al. (2002) in the Anamalais and
Kalakad-Mundanthurai Tiger Reserve). Earlier to these Bhat & Sujatha (1986) documented non-volant small
mammals in Kerala.
The intention of this study to document
the non-volant small mammal composition of the habitats of Coorg Western Ghats
was to compare the species found currently to those recorded by Shortridge 1911-12
(Ryley 1913). Although Shortridge did
not document the presence of non-volant small mammals quantitatively, his notes
provide a very good background to the qualitative aspects of the habitats, the
species and practices of land use in general. Further, other documents regarding human populations and practices are
available from gazetteers published such as those by Richter (1857) and Sathyan
(1965). There has been no subsequent
study of small mammals in this region of Western Ghats, but the vegetation and
land use have changed considerably since the early 1900s.
This study was to also understand the
impacts of macro and micro changes on small mammal composition, and to
understand the feasibility of rapid assessment of small mammal community, which
could be emulated in other locations of Bombay Natural History Society’s mammal
surveys. Since very little systematic
information on small mammals is available on modified habitats in India, this
work is a first step in understanding the same in a fast changing landscape of
the Western Ghats. This paper contains
data and analysis on species natural history, species richness and diversity.
Given the changes that have taken place
in Coorg over the last 150 years, especially in human population growth and
thereby increased conversion of natural forests into plantations and
agricultural lands (Ellouard et al. 2000), and the increasing trends in hunting
that have resulted in local extinctions or declines in large mammals (Kumara
2005), our knowledge of these impacts on small mammals is lacking. In initiating this project we assumed that
small mammals are under as much pressure from changes in vegetation,loss of
habitat quality and intensified cultivation practices over the last century and
the use of pesticides and introduction of exotic shade in the last few
decades. We expected changes in
community structure in modified habitats of Coorg to impact endemics negatively
and introduce competition from invading widespread species. This paper deals with a portion of the
overall objective to present our findings on non-volant small mammal diversity
and natural history currently in Coorg.
Materials and Methods
Study area: The district of
Coorg lies in the Western Ghats of southern Karnataka (11056’-12052’N
& 75025’-76014’E) covering an area of nearly 4,106km2;
the lowest elevation at 850m and the highest at 1745m. The eastern parts of the district extend into
the Mysore plateau at 850m, while the western part is delimited by the high
elevations peaks. The geographic features
also influence rainfall pattern which decreases substantially eastwards. The district is divided into four prominent
vegetation zones — wet evergreen forests (rainfall of 2000-5000+mm/yr), moist
deciduous forests (rainfall of 1500-2000mm/yr), dry deciduous forests (rainfall
of 800-1500mm/yr), and dry woodlands (rainfall of 800mm/yr). Two other factors that determine vegetation
changes within Coorg Western Ghats are duration of rainfall and temperature
gradient (Pascal & Meher-Homji 1986; Elouard 2000). The study was predominantly conducted in the
medium elevation evergreen forests and in moist deciduous forests.
The forested areas of Brahmagiri,
Talakaveri, Pushpagiri and Nagarahole protected areas and the adjoining reserve
forests constitute roughly 30% of the area of Coorg, while coffee and cardamom
plantations constitute 60%, paddy cultivation and open land uses constitute 8%,
and sacred groves or small- to medium-sized forest fragments make up the
remaining 2% (Bhagwat et al. 2005). Areas with dense forest cover were restricted to just over 16% (658.7km2)
of the total land area in 1997. Much of
the moist deciduous and dry deciduous forests have been converted into
plantations with roughly 2% and 1.2% remaining respectively. Only low elevation, medium elevation and high
elevation wet evergreen forests still retain dense growth amounting to
approximately 13% of the total area (Elouard et al. 2000).
Study sites: We surveyed for
small mammals in 11 locations in Coorg District (Image 1) in two vegetation
zones – medium elevation evergreen forests and the moist deciduous forests;
most of the locations were in plantations or man-modified habitats. Since official permission to conduct the
study in protected areas and reserved forests was not available, we conducted
the study in private properties consisting of plantations, agricultural fields,
open areas and forests. Although we
wished to set traps in the areas Shortridge had studied in 1911-12, due to
unavailability of permissions from the estate owners, we set up trapping
stations in estates close to the original estates (Table 1). The study was conducted sporadically from
April 2004 to April 2008 based on the availability of time and permission from
the estate owners as well as avoiding monsoons. The data gathered from this study were treated
together without separating seasonal, annual and habitat variances.
Taxonomy: The taxa of the
genus Rattus, viz. Rattus rattus wroughtoni and Rattus rattus
rufescens are referred to as distinct taxa Rattus wroughtoni and Rattus
rufescens in the paper rather than as subspecies. This is to eliminate confusion in reference
to the two taxa with overlapping distribution in contradiction to the
principles of subspecies delineation. Similarly, in light of lack of detailed taxonomic work on the endemic Suncusof the Western Ghats, the original description of Suncus niger is
recognized and the synonymy of this taxon under Suncus montanus, a
highland shrew of Sri Lanka, is ignored (Molur 2009). In all the other cases the taxonomy is after
Carleton & Musser (2005) for rodents and Hutterer (2005) for insectivores.
Trapping methods: Small mammals
can be trapped using different methods such as snap traps (Prakash et al.
1995), pitfall traps (Canova & Fasola 1991), multi traps (Laurance 1994),
and Sherman traps (Chandrashekhar-Rao & Sunquist 1996; Shanker 1998;
Prabhakar 1998; Kumar et al. 2002; Venkatraman et al. 2005). For the needs of this study, we decided not
to use snap traps as it is a violent method and not useful for mark-recapture
techniques; the wire mesh multi traps are too cumbersome and difficult to
transport; and pitfall traps are labour intensive and time consuming. We chose to use the more practical and widely
used Sherman traps of 22 x 9 x 7 cm for its ease to carry in the field, ease of
placement and handling trapped animals.
Rodents and insectivores were live
trapped in 12 broad habitat types in 11 locations in Coorg District. Traps were place in 0.50ha plots at a
distance of 10m in habitats that were big enough to support 50 traps in a
grid. In smaller habitats the grids were
suitably modified in the number of traps to accommodate maximum numbers,
keeping the inter-trap distance of 10m constant. The 0.50ha plots consisted of 50 Sherman
traps in a rectangular grid of 10 rows x 5 columns configuration. Traps were set at 10m intervals taking into
account ground and vegetation features such as runways, rocks, fallen logs,
trees and buttresses.
We used a mixture of home-made peanut
butter (without salt) with a variety of grains and pulses rolled into small
balls and placed in the trap as bait. We
checked the traps twice daily, between 0630 and 0830 hr, and 1530 and 1730 hr
for trapped animals and to replenish bait, if needed. We laid the traps for five consecutive
nights, usually placed in the afternoon of the first day and removed in the
morning of the sixth day. In some
instances when trap mortalities were noticed to occur more frequently, we reduced
the trapping sessions to four or sometimes even three nights. Animals were measured, ear tagged and
released in the same area.
Data analyses: Taxa richness
is the number of taxa in an area. In
this instance taxa richness is only of small mammals trapped. Taxa known to occur in an area through direct
or indirect evidence are excluded from analysis in this paper.
The diversity of non-volant small
mammals is analysed using the following indices as per Magurran (2004).
1.
Captures (C) is the total number of unique individuals captured on the grid.
2.
Recaptures (R) is the total number of individuals recaptured on a grid during
one trapping session.
3.
Total captures (TC) is the total number of all captures on a grid during one
trapping session.
4.
Species richness (S) is the total number of species captured.
5.
Individuals (N), is the total number of individuals of all species trapped in a
habitat.
6.
Biomass (B) is the average estimate of biomass per species.
7.
Margalef’s richness index (DMg) is estimated using the formula DMg = S-1 / lnN
8.
Shannon-Weiner diversity index (H’)is estimated using the formula H’ = ∑
Pi ln Pi, where Pi is the proportion of total
individuals belonging to the ith species in the sample.
9.
Pielou’s index of evenness (J’) is estimated using the formula J’ = H’/ln S,
where H’ is the Shannon-Weiner diversity index and S is the species richness.
10.
Simpson’s diversity index (D) is estimated using the formula D = 1 - ∑
((ni / N)2).
11.
Berger-Parker index is estimated using the formula Dominance = Nmax / N
12.
Jaccard’s Index of Similarity (Cj) on presence/absence of species is
estimated using the formula Cj = a / a + b + c, where a = the
total number of species present in both samples; b = the number
of species present only in sample 1; and c = the number of species
present only in sample 2.
13.
Morisita-Horn Index of Similarity (CMH) on abundance of different
species in habitats is given by CMH = 2 ∑ (ai x bi)
/ (da + db) (Na x Nb), where Na = the total number of individuals at site A; Nb = the
total number of individuals at site B; ai = the number of
individuals in the ith species in A; bi = the number
of individuals in the ith species in B; and da (and db)are calculated as da = ∑ ai2/Na2and db = ∑ bi2/Nb2
14.
Goodness of fit (G) is estimated using the formula G= 2 ∑ Ob x ln(Ob/Ex),
where Ob is the observed number of individuals and Ex is the expected number of
individuals.
15.
Principal Component Analysis (PCA) of non-volant small mammal diversity profile
against habitats.
16.
Correspondence Analysis (CA) depicting the dependence of presence and abundance
of non-volant small mammal species on habitat types.
Results
In an overall trapping effort of 11060
trap nights across all habitats and plantations in Coorg, 14 species of rodents
and insectivores were trapped totaling 569 overall captures (5.7%) and 412
individuals (3.79%). Rattus
wroughtoni, or the Common White-bellied Rat was the most common taxon
trapped constituting 26.2% of individuals, a distinctly higher proportion
compared to all other rodents (murids, sciurids and platacanthomyid), followed
by the two insectivores Suncus murinus or the Grey Musk Shrew
(16.3% of individuals) and Suncus niger or the Nilgiri Highland Shrew
(16.3% of individuals). Details of
overall and individual percentages of all small mammals trapped in Coorg are
provided in Figure 1. Other rodents that
were sighted, but not trapped include the Dusky-striped Squirrel Funambulus
sublineatus and the Indian Giant Squirrel Ratufa indica in
undisturbed forests.
Of the 412 individuals trapped during
the study 276 (67%) were rodents, and 33% insectivores. The Order Rodentia consisted of 239 (86.6%)
individuals from the family Muridae, 35 (12.7%) individuals from the family
Sciuridae, and two individuals (0.7%) from the family Platacanthomyidae. Overall, murids represented by nine species
formed 58% of the total traps, sciurid with one species formed 8.5%, and
platacanthomyid by one species represented 0.5%. The insectivore Order Eulipotyphla
represented by three soricid species contributed to 33% of the trap catches.
Captures and recaptures: During the
period, out of the 412 individuals captured, 157 individuals were recaptured
during the 3- to 5-night trapping exercise in each grid. The capture rates followed classical decrease
in new individuals captured on subsequent nights. The first three nights showed maximum
captures, which dropped on the last two nights rather sharply. Figure 2a shows the average proportions of
captures across five nights.
The number of trapping nights was
evaluated against mortalities and any indication of increased mortalities in
both new captures and recaptures was noticed, trapping was discontinued. Factors such as weather, temperature and ants
were taken into account in deciding whether to continue trapping efforts or
not. Overall, the first three nights
yielded up to 75% of the total captures of new individuals. Recaptures were very high on the third and fourth
nights contributing to more than 65% of all individuals recaptured during the
subsequent four nights (Fig. 2b).
The common Grey Musk Shrew Suncus
murinus was the most commonly trapped species of non-volant small mammal in
Coorg, trapped in 11 of 12 habitats, followed by the Common House Mouse Mus
musculus trapped in 10 of 12 habitats. The Nilgiri Highland Shrew Suncus niger was captured in eight of
the 12 habitats. Although Rattus
wroughtoni was the most commonly trapped species, it was trapped in only
seven of the 12 habitat types, as was the Western Ghats Striped Squirrel Funambulus
tristriatus (Table 2). Agriculture,
coffee and open areas yielded the maximum number of species (9 species each)
followed by cardamom (7), bamboo (6), banana, forest and human habitation (5
each), tea (3), orange and pineapple (2 each) and vanilla (1) (Table 2). Jaccard’s Index of similarity shows
clustering between habitats such as forest, habitation, coffee, cardamom,
bamboo, open and agriculture, and between pineapple, vanilla, orange, tea and
banana based on species richness (Fig. 3).
Trap success: The overall
effort of captures during the study yielded maximum captures in open areas
(26.2%), coffee plantations (25.2%) followed by forests (12.4%), agriculture
(10%), cardamom (9%), bamboo (7.5%), human habitation (5.3%), banana (1.9%) and
other plantations (tea, orange, pineapple and vanilla) combined (2.4%). Trap success calculated for unique
individuals caught indicated bamboo to have the highest (12.1%) followed by
forests (7%) and habitats with the highest individuals caught showed lower
overall trap success around the average of trap success of the entire exercise
(3.8%). Figure 4 indicates distinctly
higher abundances in bamboo and forests.
Trap success or abundance of species
varied widely in different habitats. The
most commonly occurring small mammal, Suncus murinus, in 11 of 12
habitats with 67 individuals captured showed a high variation in captures
between habitats, the average trap success being 0.77 (SD 1.12; Table 3). Suncus niger trapped in eight habitats
with 67 individuals captured in all showed a higher average abundance of 0.84
(SD 0.75) and lower variation compared to S. murinus. The species with relatively high overall
average abundance were Rattus wroughtoni (1.74±1.57) and R. sataraewith (1.65±2.19); the latter being mostly trapped in forests, but the one
individual trapped in the contiguous canopy of an organic cardamom plot
adjacent to a forest fragment, and one degraded forest fragment supporting none
increasing the variation. Among rodents
the common House Mouse with the second highest captures across nine habitats
showed an average abundance of 0.54 (SD 0.2). Other species with high variations in abundance between habitats were
the Jungle Squirrel, Metad and the Indian Field Mouse (Table 3). S. etruscus abundance was not
estimated as the two individuals captured were incidental.
Habitat association: In our trapping
exercise, three species indicated strong habitat associations (Fig. 5) – P.
lasiurus in forests, V. nilagirica in banana, although indirect
evidence of this species in coffee plantations were noticed even though it was
not trapped in those grids, and R. satarae with 96% of the captures in
undisturbed forests and only one individual in an organic cardamom plantation
with contiguous canopy with an adjacent forest fragment. Golunda ellioti and M. meltadashowed strong affiliation to open habitats as is evident from their traps in
ginger fields; while we trapped the former in fallow grasslands, the latter was
found on occasion in an open and a year-old coffee-areca nut plantation. These species were not trapped in any other
habitat. We found a relatively even
distribution of trap success amongst small mammals in the open and in coffee
plantation than compared to any other type of habitat (Fig. 6).
Our trapping success of small mammals in
habitats distributed across two broad vegetation zones in Coorg showed a
significant bias towards higher trap success in the moist deciduous forest zone
than in the medium elevation evergreen forest zone (Goodness of fit c2 = 30.6, df = 1, p < 0.0001;
Table 4). The abundance of small mammals
in the habitats of moist deciduous forest zone of Coorg (predominantly southern
part of the district) was significantly higher.
In a similar exercise the goodness of
fit test showed a significant difference in small mammal abundances in
different habitats across Coorg (c2 = 92.88, df =
10, p < 0.0001) with bamboo, forest and open habitats showing very high
abundance followed by habitation, and the rest of the habitats being negatively
related, with coffee and cardamom showing the lowest abundance (Table 5). The observed abundance of small mammals in
bamboos was significantly higher as compared to the expected trap success, of
about three times.
Diversity: Our studies
indicated variations in the indices of non-volant small mammal community
structure between habitats (Table 6). Shannon-Wiener Diversity Index H’, Simpson’s Diversity Index D and
Margalef’s Species Richness Index DMg were the highest in agriculture and the
lowest in vanilla. Orange showed maximum
evenness followed closely by tea, banana, pineapple and agriculture. Rattus wroughtoni was the most
abundant and dominant species in human habitation reflected in the highest
dominance calculated on Berger-Parker Index (Table 6). Similarity in species abundances across
habitats calculated by the Morisita-Horn Index revealed a tight grouping
between open, coffee, bamboo, habitation and pineapple, while cardamom, tea,
orange, vanilla, banana and agriculture showed greater similarities. Forest stood out separately from the two
habitat clades with respect to species composition and abundance (Fig. 7).
To find out whether the Shannon diversity
index is significantly different between two sites we used a modified version
of t-test by Hutcheson (1970) and Magurran (1988). The p values for the t values at given df are
given in the Table 7. The p values are
for two tail tests. At alpha = 0.05, p
values highlighted in yellow in Table 7 are significant. Since the analysis has 66 comparisons, we
used the Bonferroni correction (corrected alpha = alpha/number of tests =
0.05/66 = 0.000758). Values which are
significant after Bonferroni correction are indicated in Table 7 with an
asterisk (p < 0.000758).
Correspondence Analysis (CA) suggested
that the dependence of species abundance on habitats in Coorg is significant (c2=
586.145, p < 0.0001). CA extracted
four significant factors with eigen values more than one. While the first factor explained 38.51% of
the total variation in the data, the second explained 26.75% of the total
variation (Fig. 8).
There is a good relationship between
habitat types and the non-volant small mammal species trapped. P. lasiurus and R. satarae are
more abundant in undisturbed forests but are absent in habitation, open and
plantations. V. nilagirica is
abundant in banana plantation. M.
meltada, G. eilioti, M. booduga and B. bengalensis are
more abundant in agricultural lands. S.
niger and S. murinus are abundant in pineapple, cardamom plantation
and open habitats. R. wroughtoniis mainly associated with human habitations as also in bamboo and coffee
although it was trapped in lower numbers in several different habitats, R.
rufescens in coffee and bamboo, and M. musculus is abundant in
vanilla, tea and orange plantations; suggesting that small mammals show habitat
preferences.
A principal component analysis (PCA) of
the non-volant small mammal data was carried out to understand diversity
profiles amongst habitats. The PCA
extracted two significant factors with eigen value of more than one. The first factor explained 78.26% of the total
variation in the data and the second factor explained 16.33% of the total variation. On the first factor Simpson’s diversity index
showed maximum factor loading followed by Shannon index and Margalef’s richness
index. Berger-Parker index had high magnitude on the negative axis of first
factor. Number of individuals had maximum factor loading on the second factor
followed by number of species. Evenness index had maximum magnitude on the
negative axis of second factor (Fig. 9).
Habitats such as vanilla, pineapple,
tea, orange and habitation exhibit low diversity and organisms with higher
Berger-Parker dominance index, i.e. few taxa with high abundance. The habitats also show higher evenness
despite a few taxa dominating, due to very few individuals and species present
in them. Agriculture and banana have
higher evenness index. Open and coffee
habitats have higher individuals, greater species richness and relatively less
evenness. Forest has high number of
individuals and species, however, it also exhibits lower diversity due to less
evenness as some species are more abundant than others.
We trapped eleven species of rodents and
three species of shrews in all during the study. We report new distribution records for the
forest rat Rattus satarae in Coorg, earlier known only from the type
locality of Satara and the Nilgiris (Hinton 1918; Verneau et al. 1997; Musser
& Carleton 2005). Similarly, we
report range extension for Vandeleuria nilagirica in central and
northern Coorg; the earlier records were from the Nilgiris and Kutta in
southern Coorg (Corbet & Hill 1992).
Species
account:
Funambulus tristriatus (Waterhouse,
1837) [Western Ghats Striped Squirrel, Jungle Palm Squirrel] (Image 2).
We found this species to be quite shy in
the northern wet evergreen forests than in the southern moist deciduous forests
of Coorg. The squirrels were also more
visible in the southern plantations and were either shier or less abundant as
one went north. Although we did not set
traps specifically for this squirrel, they seemed more willing to be trapped in
southern Coorg. We also found the
specimens from the south to be hardier than those in the north; their reaction
to being trapped and being handled distinctly different and more tolerant in
the southern parts. The 35 individuals
contributed to 8.5% of the total, and 12.7% of all rodents trapped during the
study. The species does not like being
trapped as is evident from the very low percent (5.7%) of recaptures. During the summer of 2007 we observed several
specimens in an area suffering from a disease, which seemed to have had spread
through much of the population (>90% of individuals affected).
Bandicota
bengalensis(Gray, 1835) [Lesser Bandicoot Rat, Indian Mole Rat] (Image 3)
We trapped this species in an organic
paddy field close to the Brahmagiri Wildlife Sanctuary, southern Coorg, and in
a newly converted (9-10 year old) forest patch to coffee-arecanut plantation
3km south of Madikeri town in northern Coorg. In both the cases the traps were about 50m from the nearest forest
fragment. Indications of the existence
of species in other places were meager, with no serious complaints from
planters or workers about their destructive role to plantations. This species contributed to 1.7% of the total
captures, 2.5% of rodents, and 2.9% of murids captured during the study. Only one of the seven individuals was
recaptured.
Golunda
elliotiGray, 1837 [Indian Bush Rat] (Image 4)
We trapped this species from one
location in northern Coorg and one in the plains of eastern Coorg; the former
in the fallow grasslands of a discontinued paddy field in a freshly converted
ginger field at about 1000m, and the latter in a ginger plantation (850m) on
the banks of river Cauvery. The species
was never captured in plantations or forests. Surveys amongst plantation owners and labourers indicated no berry
predation by rodents, and complete ignorance to the presence of this species,
probably an indication of its non-destructive role at least in coffee
plantations. Although very common in
peninsular India, we did not find this species to be common in Coorg basing on
trap success and informal surveys with locals and agricultural labourers. G. ellioti contributed to only 1.2% of
all the captures, 1.8% of rodents, and 2.1% of all murids captured during the
study. There were no recaptures.
Millardia
meltadaGray, 1837 [Soft-furred Field Rat, Metad] (Image 5)
We recorded this metad in only one
location at about 850m, in a ginger field on the banks of river Cauvery at
Kushalnagar. It was distinctly absent
from all other locations including forests, plantations, fallow grasslands, and
agricultural patches of the hilly Coorg terrain. The species formed a very small proportion
(2.2%) of the small mammals, 3.2% of rodents and 3.8% of all murids trapped in
Coorg. The Metad showed the highest rate of recapture (89%) with 75% of the
animals recaptured more than once. In an
interesting episode, one individual that was captured on the first trap night
had been ear tagged and kept in captivity for observation. On the fifth day of the session, while we
were photographing the animal, the metad escaped. The next morning on checking the traps of the
fifth night, the individual was trapped in the exact same trap as in the first
instance on night one. The animal had
escaped nearly 1km away from the trapping grid, but had returned to the grid
within 12 hours (he escaped around 18.30hr) crossing coffee and bamboo
plantations, a elephant trench and a pond.
Mus
boodugaGray, 1837 [Little Indian Field Mouse, Indian Pygmy Field Mouse] (Image 6)
In our study, it was a common grassland
species trapped in four habitats, especially close to water bodies, but not as
frequently as M. musculus. It
occurred usually along with Mus musculus, a species with which it is
easy to confuse with. The adults of this
species are small compared to M. musculus, but unless several
individuals are handled and measured, it is difficult to distinguish the
two. M. booduga is more docile
compared to M. musculus, and is very sensitive to handling compared to M.
musculus. The species constituted
nearly 5% of the total small mammals trapped, 7.2% of all the rodents (n=277),
and 27.4% of the Mus spp. (n=73) trapped during the study. Only one of the 20 individuals trapped was
recaptured. In two instances two
individuals were trapped together in a Sherman trap; in both the cases we found
an adult male-female pair.
Mus
musculusLinnaeus, 1758 [House Mouse] (Image 7)
This was trapped more often than Mus
booduga. Although confusing, in the
juvenile age class, to distinguish the two species, adult Mus musculusare distinctly larger and heavier than adult Mus booduga. It was trapped in 10 of the 12 habitats; most
surprisingly, it was not trapped in and around human habitation. 12.9% of the total captures were of M.
musculus, 19.2% of all rodents, 22.2% of murids and 76.2% of the Musspp. trapped. During the study the
highest proportion were trapped in coffee plantations (22.6%) followed by
cardamom and grass (20.8% each).
Rattus
rufescens(Gray, 1837) [Buff-bellied Rat]
Recognised as a subspecies of Rattus
rattus, this taxon occurs along with another subspecies R. r. wroughtoniin some areas, especially in coffee plantations (50% of the catches), grass and
agriculture. It was not very commonly
trapped compared to the other two rats. It formed 2.4% of the total captures, 3.6% of rodent captures, 4.2% of
murid captures and 7% of the total rats captured during the study. Compared to R. wroughtoni, this taxon
exhibited relative calmness in the trap, while being handled and when
released. The snout is not as long as inR. wroughtoni, and the skull seems more robust on the exterior compared
to the former. Morphometric data
revealed a distinct difference from the other two rats, indicating the need for
recognising this rodent as a species rather than a subspecies within the Rattus
rattus complex. From our study it is
clear that this taxon is still extremely rare compared to the other two
white-bellied rat taxa and not confirming to Shortridge’s prediction, it has
not replaced the white-bellied rats anywhere in our study sites in Coorg.
Rattus
wroughtoni(Hinton, 1919) [White-bellied Rat, Common House Rat, Black Rat]
This species was the most commonly
caught taxon during the trapping effort; it contributed to 26.2% of the
total. A rather skittish rat compared to
the other two, when handled it ‘yelps’ in a high squeak, hops excitedly in the
bag and is rarely still. The underside
is grey or white unlike R. rufescens, which is buff coloured, the morphological
characteristics of this taxon separates from the other two rats. Although there are slight overlaps in the
range of its morphometrics with the other two rats, the head-body to tail ratio
in this taxon falls in between the ratios of the other two taxa (rufescens< wroughtoni < satarae), so are the head-body and tail
lengths (again, rufescens < wroughtoni < satarae)
(Molur et al. in prep.). Caught in eight
habitats, the highest trap rate was in coffee followed by grass. It constituted 39.1% of rodents, 45.2% of
murids, and 76.1% of the three rats trapped in Coorg.
Rattus
satarae(Hinton, 1918) [Western Ghats Forest Canopy Rat, Sahyadri Forest Rat] (Image 8)
In our study, this highly restricted
species was found mainly in habitats such as undisturbed forest fragments and
in one instance in an undisturbed, organic cardamom plantation with native
vegetation, closed canopy and next to an undisturbed forest patch. Mainly caught in traps set on vines and tree
trunks, this species was very docile, almost wanting to be handled, very
curious and unafraid, although shy. All
of the trapped individuals, without exception, stayed calm within the trap even
when the trap walls were collapsed, and cooperated during handling and
measurements. When released, the animals
examined the surroundings patiently, as did they examine us and reluctantly
scampered away towards the nearest tree or vine and climbed up. In all cases where the animal was released
close to the forest it was trapped from, the released animal assessed the
surroundings and moved in the direction of the forest fragment. 96% of the species were caught in forests; it
contributed to 5.8% of the total traps, 8.7% of rodents, 10% of murids, and
16.9% of all rats.
Vandeleuria
nilagiricaJerdon, 1867 [Nilgiri Pencil-tailed Tree Mouse] (Image 9)
The specimens of Vandeleuria
nilagairica we caught in the banana plantation had longer tails and
grayish-white underparts and differed from specimens we had examined from
Alibagh in Maharashtra and Anaikatty in Coimbatore (both V. oleracea and
in the Western Ghats). We also observed
their nests in a coffee estate in northern Coorg (Haleri Estate, Haleri,
1000m), in only one small part of the area. The nests had been constructed that season, used during the previous
breeding and development stage between October and March, and abandoned. This assessment was also supported by an old
plantation worker with a keen interest in natural history, who has been
observing their behaviours for over 50 years. We counted 20 nests and estimating an adult pair in each nest with two
or three young, the number of individuals in that patch was estimated at
between 80 and 100. On another occasion
we noticed the presence of this species in a coffee plantation at about 950m
and based on the characteristic mint-smelling droppings in and around the traps
(see Molur et al. in prep.), we deduced that the species had managed to steal
the bait by using its long prehensile tail for hanging from a branch overhead
or from the trap roof to enter and eat the bait, and leaving its scat as
evidence. The species contributed to a
very meager proportion of the entire trapping exercise of just 0.7%, 1.1% of
all rodents, and 1.3% of all murids.
Platacanthomys
lasiurusBlyth, 1859 [Spiny Tree Mouse, Malabar Spiny Tree Mouse] (Image 10)
This unique species, a spiny tree mouse,
was trapped only on two occasions in a private undisturbed riverine forest
adjacent to the Brahmagiri Wildlife Sanctuary at about 850m. Of the six forest fragments we surveyed in
Coorg, the species was present in only this patch, showing a preference to
forest contiguity and nondisturbance. Of
the two individuals caught, one was recaptured on the third and fourth nights. The proportion of catches were 0.5% of the
total, and 0.7% of all rodents. This
species is considered a pest of pepper based on very limited observations
(Jason 2006), but in all our surveys of pepper growers in Coorg, not one estate
owner or labourer complained about pepper crop damage from any rodent; and that
they had never seen a rodent like P. lasiurus in their estates or
anywhere else. The only damage to pepper in Coorg was due to fungal attacks.
Suncus
etruscus(Savi, 1822) [Pygmy Shrew, Etruscan Shrew] (Image 11)
A rather cryptic species, we found it
once in open and around human habitation habitats each as incidental
catch. We initially confused the
individuals, a male and a female, for baby Suncus sp., but on further
examination realized they were adults of S. etruscus. The female weighed a mere 1.5g, while the
male was about 2g.
Suncus
murinusLinnaeus, 1758 [Grey Musk Shrew, Asian House Shrew] (Image 12)
The commonest of shrews in India, the
taxon found in Coorg closely resembles S. murinus, but has to be genetically
examined for its affinities. The species
is much smaller than the northern Indian S. murinus, but is distinctly
different from the conspecific S. niger. S. murinus is grayish overall, with whitish patches under the
neck and distinct pink muzzle, hands, feet, tail and ears. The animal exhibited behavioural differences
from S. niger in being very restless and squeaking when handled, and
producing the characteristic musk odour. The most widely adapted species; we trapped this species in 11 of the 12
habitats in Coorg, with the highest proportion of traps in grass followed by
coffee plantations. It constituted 16.3%
of the total non-volant small mammals, and 49.3% of all shrews trapped.
Suncus
nigerHorsfield, 1851 [Nilgiri Highland Shrew] (Image 13)
This taxon is distinct in morphological
and behavioural characters compared to S. murinus and we trapped it in
eight of the habitats in Coorg along with S. murinus. Similar to S. murinus, S. nigerconstituted 16.3% of the total non-volant small mammals, and 49.3% of all
shrews trapped. Like S. murinus, S.
niger was trapped most in grass followed by coffee plantations. However, unlike S. murinus, S.
niger is black overall with no greyish tinge under the neck; the hands,
feet, tail, ears and muzzle are black or distinctly dark. The tail is black, slender and angular with
short black hairs compared to S. murinus’s tail which is thick, pink and
has long white vibrosae. Trapped
individuals of S. niger were more docile, cooperative during handling
and measuring, non-squeaky and did not leave any musky odour. The inguinal mammae arrangement in S.
niger is distinctly different from those of S. murinus with the
first two closer in S. niger, while all three separated equally from
each other in S. murinus. In the
males, the penis head of S. niger is red, while it is white in S.
murinus.
During the study, we observed the
presence of a few non-volant small mammals occuring in certain habitats, mostly
prominent ones such as giant squirrels, gliding squirrel and the common Indian
bandicoot. We observed the Indian Giant
Squirrel Ratufa indica in the forests of Brahmagiri, Pushpagiri and
Talakaveri wildlife sanctuaries, Nagarahole National Park and in reserve
forests of northern and western Coorg. Local knowledge revealed their presence in three of the six forest
fragments we surveyed, indicating a strong preference to less disturbed
fragments as well as closeness to larger forest areas. Of the two gliding squirrels, we observed
only the Large Brown Gliding Squirrel Petaurista philippensis in three
locations – all three forest patches. There were occasional reports of these squirrels by estate owners who
reported that their frequency had declined drastically in plantations over the
years. We did not observe the endemic
smaller Travancore Gliding Squirrel Petinomys fuscocapillus nor did we
gather any evidence of their existence from the locals, who very distinctly
remember the gliding squirrels to be fairly big in size leading us to assume
they were P. philippensis and not P. fuscocapillus. During the four years of our survey we did
not observe a single Greater Bandicoot Rat Bandicota indica in any
location throughout Coorg. However, we
did come across several burrows in different locations, mainly in and around
human habitations, cow sheds, granaries, coffee drying yards and kitchen
gardens in estates close to townships. Estate owners also complained of the ‘nuisence value’ of these
bandicoots to their vegetable patches. We did not observe burrows of this species in any forested area,
fragments or in plantations. Although
species such as the Dusky-striped Squirrel Funambulus sublineatus,
White-tailed Wood Rat Madromys blanfordi, Brown Spiny Mice Mus platythrixand M. saxicola, and Petinomys fuscocapillus have been reported
in Coorg or adjacent areas such as Wynaad before (Ryley 1913; Nandini Rajamani
pers. comm., P.O. Nameer pers. comm.), we did not trap or observe these species
throughout the four years of study in Coorg. We did not observe or trap in Coorg endemic species that occur in the
neighbouring Nilgiri Biosphere Reserve such as Bonhote’s Mouse Mus famulusand Day’s Shrew Suncus dayi. Surprisingly, our efforts of 11060 trap nights did not yield a single
specimen of the widely distributed and commonly occuring Indian Gerbil Tatera
indica.
Discussion
India has around 110 species of rodents
and shrews and about 30 species in the Western Ghats (Molur et al. 2005), but
when the different studies on non-volant small mammals over the last two
decades are analysed, only a few species have been recorded in each study,
viz., five in Anamalais (Chandrasekar-Rao & Sunquist 1996), seven in
Mudumalai Wildlife Sanctuary (Venkatraman et al. 2005), six in Kalakad-Mundanthurai
Wildlife Sanctuary (Mudappa et al. 2001; Kumar et al. 2002), five in the
Anamalais (Mudappa et al. 2001; Kumar et al. 2002), eight in the Anamalais
(Prabhakar 1998), eleven in the Nilgiris (Shanker 2003). Our study revealed 11 species of rodents and
three species of shrews in various habitats of Coorg. Species composition in Coorg differed from
the earlier studies in that three species recorded in some areas, Tatera
indica, Madromys blanfordi and Mus platythrix were not
trapped during our studies anywhere in Coorg. Species richness in different habitats of Coorg is much higher than
those of other studies until now.
Funambulus
tristriatus(Waterhouse, 1837) [Western Ghats Striped Squirrel, Jungle Palm Squirrel]
(Image 2).
This is an endemic Western Ghats species
distinct from the plains Funambulus palmarum in being bigger and darker
in colour. A rather shy creature, this
species was trapped more often in the southern parts of the district (moist
deciduous forests) than in wet evergreen forests of the northern parts. Ryley (1913) identified this species as Funambulus
wroughtoni, however, Thorington & Hoffmann (2005) consider F.
wroughtoni as a synonym of Funambulus tristriatus. Shortridge (in Ryley 1913) commented that F.
wroughtoni were locally plentiful in Coorg and distinctly uncommon in some
places. He noticed this species to be
conspecific with F. tristriatus and F. palmarum in many parts of
southern India, and presumed they experienced local die-offs due to epidemics
such as bubonic plague. He commented on
the existence of many variations in the marking and colouration of these
squirrels in Coorg.
The
species’ wide distribution in the Western Ghats with relatively few threats
makes it a species of Least Concern (Molur et al. 2005) as per the 2009 IUCN
Red List of Threatened Species (Molur & Nameer 2008a).
Bandicota
bengalensis(Gray, 1835) [Lesser Bandicoot-Rat, Indian Mole Rat] (Image 3)
This species of bandicoot rat is so
different looking from its congeners, Wroughton (1908) placed it under a
separate genus Gunomys. Several
workers have indicated its difference and suggest that it does not belong to
the genus Bandicota due to morphological, genetic and chromosomal
variations (Pradhan et al. 2005; Sharma & Raman, 1971, 1973). However, due to lack of any systematic study,
it is still placed under the genus Bandicota (Musser & Carleton
2005). G.C. Shortridge in Ryley (1913)
recorded the presence of Gunomys kok in Coorg, which at the present
moment is considered a synonym under Bandicota bengalensis until further
systematic investigations are carried out. B. bengalensis is widely distributed in India and also occurs in
its immediate neighbouring countries of Nepal, Pakistan, Bangladesh and Sri
Lanka (Molur et al. 2005). Since it has
a very wide distribution in the region and not impacted by threats, it is
categorized as Least Concern by Molur et al. (2005) and the 2009 IUCN Red List
of Threatened Species (Aplin et al. 2008a).
This rat is distinguished from Bandicota
indica in being smaller in size and having a smaller skull. Behaviourally, this species is calmer and
relatively less aggressive compared to B. indica. In Coorg, we observed burrows of this species
(distinctly smaller than those of B. indica) close to wooded areas and very
rarely in agricultural areas, grasslands or fallow lands. Morphological measurements of the different
populations in India indicates a wide variation in Head-body length of
130-260mm, Tail length of 99-162mm, and Hind foot length of 27-48mm (Agrawal 2000). The rat is grayish-brown to black in dorsal
colouration; specimens in Coorg with slightly more reddish tinge. Ventral colouration is light to dark gray,
and the tail more uniformly darkly coloured.
G.C. Shortridge in Ryley (1913)
estimated this species to be plentiful in deciduous and evergreen forests and
around cultivation in Coorg. He
collected specimens of this species only from southern Coorg in Wotekolli,
Makutta, Virajpet and Srimangala. He
mentions the destructive role of this species on young rubber plants, their
tubers being eaten by this rodent. Due
to their subterranean habit, he says, they are difficult to exterminate.
Golunda
elliotiGray, 1837 [Indian Bush Rat] (Image 4)
This is a monotypic genus with a fairly
wide distribution in India and the neighbouring countries of Nepal, Pakistan
and Sri Lanka (Molur et al. 2005) and extending only a little into southeastern
Iran (Musser & Carleton 2005). While
Ellerman (1961) listed seven subspecies, Agrawal (2000) does not find any
geographic variation in this species. It
is found in varied habitats of dry deciduous, scrub and grass; ventures into
cultivated lands, orchards and grasslands close to streams. It builds nests in thick bush and is found in
an elevation range of 100-1300m in India (Molur et al. 2005). G.C. Shortridge (in Ryley 1913) describes it
as “probably plentiful”, and although seen in coffee estates, does not inflict
sufficient damage to the berries and do not appear to be sufficiently
numerous. Molur et al. (2005) and the
2009 IUCN Red List of Threatened Species (Molur & Nameer 2008b) categorize
this species as Least Concern due to its wide distribution and no major threats
affecting its population.
G.C. Shortridge (in Ryley 1913)
commented on the species being probably plentiful in coffee plantations. They moved around in lantana thickets or
other undergrowth and he presumed they fed on coffee berries. He trapped four specimens from three
locations in southern Coorg, namely, Wotekolli, Virajpet and Kutta.
Millardia
meltadaGray, 1837 [Soft-furred Field Rat, Metad] (Image 5)
The Soft-furred Metad is quite common in
its distribution in India and neighbouring countries of Sri Lanka, Pakistan and
Nepal (Molur et al. 2005). Although it
bears close resemblance to Golunda ellioti, it can be easily recognized
for its characteristic softer fur, five plantar pads and lack of a groove on
its incisors. Ellerman (1961) recognized
subspecies, but Agrawal (2000) does not recognize subspecies as he did not find
any geographic variations. It commonly
occurs in grasslands, cultivated lands, irrigated lands, embankments and rocky
hills; found from sea level up to 2670m in India (Molur et al. 2005). G.C. Shortridge (in Ryley 1913) trapped this
species in Huvinakadu estate in southern Coorg in a thick scrub patch close to
a deciduous forest (apprx. 900m) and was surprised to see it since its affinity
is to treeless environs in agricultural patches in Deccan India.
While Chandrashekar-Rao & Sunquist
(1996) and Prabhakar (1998) do not report trapping this species from the Indira
Gandhi Wildlife Sanctuary between 1000-1700m in the Anaimalai hills, Jayson
(2006) reports it being trapped only in Chimmony Wildlife Sanctuary at an
altitude of 450m in Kerala. North of the
Palghat gap, Shankar & Sukumar (1999) trapped M. meltadaoccasionally in the periphery of sholas in the Nilgiris between 1800-2500m.
Molur et al. (2005) and the 2009 IUCN
Red List of Threatened Species (Molur & Nameer 2008c) categorize this
species as Least Concern due to its wide distribution and no major threats
affecting its population.
Mus
boodugaGray, 1837 [Little Indian Field Mouse, Indian Pygmy Field Mouse] (Image 6)
This mouse is sometimes difficult to
distinguish in the field from Mus musculus. It has a wide distribution in India and the
neighbouring countries of Nepal, Bangladesh, Pakistan and Sri Lanka, found at
elevations from sea level up to 4000m (Molur et al. 2005). Marshall (1977) recognized Mus dunnito be very different from Mus booduga due to incompatible chromosomes
and differences in molar shape and body colour; but Agrawal (2000) treated bothMus dunni and Mus terricolor as synonyms under Mus booduga. It occurs in agricultural fields, grasslands,
scrub jungles, near water bodies and occasionally in plantations (Molur et al.
2005). G.C. Shortridge (in Ryley 1913)
noted that the species lives underground or under stones and observed a round
grass nest with young of this species in Nagarahole.
This species is considered the smallest Musin the Indian subcontinent with head-body length ranging from 50-87mm, tail
length of 51-72mm, and hind foot length of 13-17mm (Agrawal, 2000). Shortridge (in Ryley 1913) reported trapping
this species in six locations. Although
Chandrashekar-Rao & Sunquist (1996) and Shanker & Sukumar (1999) do not
report this species in their trapping efforts, Prabhakar (1998) trapped them in
seven forest fragments of Anaimalai hills.
It is categorized as Least Concern by
Molur et al. (2005) and the 2009 IUCN Red List of Threatened Species (Aplin et
al. 2008b) due to its wide distribution and no apparent major threats.
Mus
musculusLinnaeus, 1758 [House Mouse] (Image 7)
This rodent is the commonest mouse in
the world with a very wide distribution all across except in the Antarctic,
thanks to its association with humans and their movements across the globe
(Ellerman & Morrison-Scott 1951; Musser & Carleton 2005). Agrawal (2000) recognized three subspecies in
India. G.C. Shortridge (in Ryley 1913)
reported Mus manei in three locations in Coorg “very abundant around
houses”. The taxon in Coorg is not
usually found inside houses and therefore does not fall under Mus musculus
castaneus, one of the three subspecies recognized by Agrawal (2000) as an
indoor mouse occurring all over India. The other two recognized subspecies do not occur in the south. It is slightly larger than Mus booduga,
but sometimes difficult to tell apart in the field. Geographical variation in size is very
obvious in this species. As it is
widespread and is not threatened with any risk of extinction, it has been
categorized as Least Concern by Molur et al. (2005) in India and by Musser et
al. (2008) globally in the 2009 IUCN Red List of Threatened Species.
Rattus
rufescens(Gray, 1837) [Buff-bellied Rat]
This is one of the several recognized
subspecies of Rattus rattus (Linnaeus, 1758) in India. It is distinct from the other common Indian
subspecies R. rattus wroughtoni in having a reddish dorsal fur and buff
coloured ventral fur. This is a widely
distributed subspecies occurring in the western and southern parts of India and
in neighbouring Pakistan (Ellerman 1947). G.C. Shortridge (in Ryley 1913) refers to individuals with both grey and
white underparts as Epimys rufescens saying the darker bellied form is
quite rare and alien and could replace the native white-bellied form by
interbreeding. He may have referred to
either Rattus satarae or R. rattus wroughtoni as the
white-bellied forms.
Rattus
wroughtoni(Hinton, 1919) [White-bellied Rat, Common House Rat, Black Rat]
This is the most common Indian rat
distributed almost all over the country; at least this is the name given to all
the white-bellied rats around the country by several workers. This is distinctly smaller than Rattus
satarae with the tail being less than 115% of head-body length (Ellerman
1947). This taxon occurs in all types of
habitats, rarely preferring undisturbed forests; occupies any habitat that is
influenced by human action. It is likely
that the taxon has replaced other native forms as and when humans have moved
into wilderness areas.
Rattus rattus as a species is
categorized as Least Concern in India by Molur et al. (2005) and by Amori et
al. (2008) in the 2008 IUCN Red List of Threatened Species. As the taxa in this complex such as R.
rattus rufescens and R. rattus wroughtoni are to be taxonomically
worked out, we have for purposes of clarity and ease used Rattus rufescensand Rattus wroughtoni as species rather than subspecies. By definition, two subspecies cannot occupy
the same location, which in the case of our work in Coorg indicates this in
some of the habitats.
Rattus
satarae(Hinton, 1918) [Western Ghats Forest Canopy Rat, Sahyadri Forest Rat] (Image 8)
This unique canopy rat has been elevated
to a full species by Musser & Carleton (2005) based on Gordon Corbet’s
comments that the subspecies identified by Hinton (1918) has a karyotype 2n =
42 as against the Rattus rattus wroughtoni subspecies, which has 2n =
38. This forest rat is morphologically
distinct from Rattus rattus wroughtoni, which is usually what this
species is confused with by several researchers. The tail length to head-body ratio is much
larger than that of R.r. wroughtoni (Musser & Carleton 2005). The species has a disjunct distribution in
Satara, Coorg and the Nilgiris, mainly due to lack of any systematic
collections and proper identification. It is suspected to occur in all Western Ghats forests throughout the
chain ranging in elevation from 700 to 2150m. It occurs in pristine or undisturbed forest habitats, usually restricted
to the canopy of tall trees and vines, occasionally coming down to the
ground. It is primarily an insectivore
also eating fruits during season (Molur & Nameer 2008d). Presently, this species has been categorised,
based on available information, distribution, range and threats, as Vulnerable
by Molur & Nameer (2008d) in the 2009 IUCN Red List of Threatened Species.
Vandeleuria
nilagiricaJerdon, 1867 [Nilgiri Pencil-tailed Tree Mouse] (Image 9)
This species had been either synonymised
under Vandeleuria oleracea (Ellerman 1961; Agrawal 2000) or kept as a
separate species (Corbet & Hill 1992; Musser & Carleton 2005). It had earlier been recorded only from the
Nilgiris, but Molur & Nameer (2008e) provide additional information about
its distribution in Coorg Western Ghats. It occurs from 900 to 2100m, usually found in moist deciduous forests,
coffee, cardamom and banana plantations in Coorg, preferring native tree
canopies (Molur & Nameer 2008e). It
differs from a closely resembling species Vandeleuria oleracea in having
a darker and slightly bigger body, and longer tail. Unlike V. oleracea, V. nilagiricais rarely seen indoors. Based on
restricted and fragmented distribution, and threats to its habitat, it is
categorized as Endangered by Molur & Nameer (2008e) in the 2009 IUCN Red
List of Threatened Species.
V. nilagirica is different
from V. olaracea in having a longer tail and grayish-white underparts
(Musser & Carleton 2005). The
specimens we caught in the banana plantation matched these characters and
differed from specimens we had examined from Alibagh in Maharashtra and
Anaikatty in Coimbatore (both V. oleracea and in the Western
Ghats).
Family
Platacanthomyidae:
This unique family is represented by
only three species worldwide and only one species in India (Musser &
Carleton 2005). The species of this
family were earlier considered under the dormouse family Gliridae (Ellerman
1961). However, its affiliations to
Muroidea were established by several workers (see Musser & Carleton 2005).
Platacanthomys
lasiurusBlyth, 1859 [Spiny Tree Mouse, Malabar Spiny Tree Mouse] (Image 10)
Popularly known as the Malabar Spiny
Dormouse, Musser & Carleton (2005) renamed it as Spiny Tree Mouse because of
its affiliation to murids rather than glirids (dormice) so as to avoid
perpetuating incorrect phylogeny. It is
endemic to the Western Ghats in the states of Karnataka and Kerala, distributed
between the elevations of 600 and 2000m. It prefers undisturbed deciduous and evergreen forests and riparian
habitats. It is predominantly an
arboreal species coming down to the ground on occasions. It prepares nests in tree holes (Molur et al.
2005; Jason 2006). It has been termed a
pepper pest in Kerala and like the rest of the rats and mice is classified as a
Vermin in the Indian Wildlife (Protection) Act of 1972. Due to restricted distribution, severe
fragmentation and threats to its populations and habitat, it was categorized as
Vulnerable by Molur et al. (2005) and Molur & Nameer (2008f) in the 2009
IUCN Red List of Threatened Species.
Order
Eulipotyphla
This Order, until recently (Hutterer
2005), was called Soricomorpha and clubbed with other orders like
Erinaceomorpha under Order Insectivora. It is now separated to include all shrews (IUCN 2009).
Family
Soricidae:
The shrews in India placed under Family
Soricidae are represented by 24 species of nine genera (Molur et al.
2005). Five taxa occur in southern India
with one endemic to the Western Ghats. The
Sri Lankan endemic, Feroculus feroculus, the long-clawed shrew was
recently reported from the Nilgiris (Pradhan et al. 1997) in India. A systematic study is needed to determine if
it is a subspecies or a new species.
Suncus
etruscus(Savi, 1822) [Pygmy Shrew, Etruscan Shrew] (Image 11)
This is the smallest non-volant small
mammal and occurs in Asia, Africa and Europe. Two subspecies in southern India have been tentatively recognized – S.
etruscus macrotis and S. etruscus nilgirica (Hutterer 2005). G.C. Shortridge’s (in Ryley 1913) collection
of Pachypus perrotteti is synonymised under Suncus etruscus nilgirica(Anderson, 1877). Very few records of
the shrew exist in India although it is presumed to have a wide distribution in
the country and its neighbours. It
occupies forested as well as rural landscapes and occurs from sea level up to
5000m (Molur et al. 2005). It is so
small and light, one needs a highly sensitive Sherman trap to capture it. It is categorized as Least Concern in India
(Molur et al. 2005) and globally (Aulagnier et al. 2008) in the 2008 IUCN Red
List of Threatened Species.
Suncus
murinusLinnaeus, 1758 [Grey Musk Shrew, Asian House Shrew] (Image 12)
This is the commonest shrew found widely
distributed in India and the neighbouring countries of Pakistan, Bhutan,
Bangladesh, Nepal and Sri Lanka (Molur et al. 2005). It lives in all kinds of habitats and also in
human habitation. It occurs from sea
level up to about 3700m altitude. There
are several genetically distinct forms within this species complex (Hutterer
2005). The wide distribution of the
species is primarily due to human movement and settlements (Hutterer
2005). It is a Least Concern species in
India (Molur et al. 2005) and also globally (Hutterer et al. 2008)
according to the 2008 IUCN Red List of Threatened Species.
Suncus
nigerHorsfield, 1851 [Nilgiri Highland Shrew] (Image 13)
This shrew is endemic to the Western
Ghats of India and is recognized as a subspecies of Suncus montanus by
Hutterer (2005). Suncus montanusis a Sri Lankan highland shrew and the nominate subspecies is endemic to that
country. Suncus niger closely
resembles this species and for want of systematic studies, the two species have
been synonymised. Based on geographical barriers,
and the fact that the taxa have not bred naturally over many millennia, we
consider the subspecies as a distinct species as was originally described by
Horsfield in 1851. Suncus montanusoccurs in evergreen, moist deciduous forests and grasslands between 900 and
2400m elevation. It has been assessed as
Vulnerable by Molur et al. (2008) for the IUCN Red List of Threatened Species.
This taxon is distinct in morphological
and behavioural characters compared to S. murinus and we trapped it in
eight of the habitats in Coorg along with S. murinus. Similar to S. murinus, S. nigerconstituted 16.3% of the total non-volant small mammals, and 49.3% of all
shrews trapped. Like S. murinus, S.
niger was trapped most in grass followed by coffee plantations. However, unlike S. murinus, S. nigeris black overall with no greyish tinge under the neck; the hands, feet, tail,
ears and muzzle are black or distinctly dark. The tail is black, slender and angular with short black hairs compared
to S. murinus’s tail which is thick, pink and has long white
vibrosae. Trapped individuals of S.
niger were more docile, cooperative during handling and measuring,
non-squeaky and did not leave any musky odour. The inguinal mammae arrangement in S. niger is distinctly different
from those of S. murinus with the first two closer in S. niger,
while all three separated equally from each other in S. murinus. In the males, the penis head of S. nigeris red, while it is white in S. murinus.
Rattus rattus is the most
commonly prevalent rodent recorded in all the areas in the Western Ghats in
previous studies. The white-bellied
form, which is prevalent in the area seems to be composed to two distinct taxa,
viz. R. wroughtoni and R. satarae, the latter just recently
recognized as a distinct species. Apart
from Shanker’s (2003) comment on the white-bellied form in the Nilgiris could
be of two taxa, all the studies assume the rat to be a single taxon. In our studies, the three taxa of rats, viz. Rattus
rufescens, R. satarae and R. wroughtoni, were easily
distinguishable by their morphology, morphometrics, habit and behaviours (Molur
et al. in prep.). While R. sataraewas the calmest and most cooperative of all three, it was also the only species
caught on traps set on trees and on vines. On occasions this species was caught in traps on the ground, but most of
the catches were of individuals captured for the second or third time. R. rufescens and R. wroughtoniwere mostly caught in traps on the ground, but R. wroughtoni was also
caught in traps on bamboos in that habitat. R. rufescens and R. satarae were never trapped in bamboo.
The non-volant small mammal trap success
varied widely in our study in different habitats in Coorg. While 13 grids did not yield us a single
animal, the highest trap success was 42% in one of the grids. The average trap successes across 70 grids,
totaling 11060 trap nights and a total catch of 412 individuals, was
3.79%. This is one-third the trap
success reported by Shanker (1998, 2003; 10.6%) for small mammals in his work
in the montane ecosystems of the Nilgiris. Venkatraman et al. (2003) reported a higher trap success in the tropical
forest habitats of Mudumalai Wildlife Sanctuary in Tamil Nadu of 5.3%;
Prabhakar (1998) reported an overall trap success of 5.4% in the tropical
rainforests of the Anaimalai hills; Chandrashekar (1989) and Chandrashekar-Rao
& Sunquist (1996) reported an average trap success of 5.6% (including
recaptures; 2.5% excluding recaptures) in the habitats of Anaimalais; and Kumar
et al. (2002) reported about 2.14% from the forests of Kalakkad-Mundanthurai
Tiger Reserve, 3.5% from the forest fragments of Anamalais and 5.4% from the
surrounding matrix in the Anamalais. In
our study trap success in the forest grids was 7.2% higher than most trap
successes from previous studies except in the Nilgiris by Shanker (2003);
however, the average trap success in the rest of the man-modified habitats was
only 3.5% in Coorg, a clear reversal of the situation reported by Kumar et al.
(2002) in the Anamalais. While changes
in habitat quality affect endemic species composition with commensals replacing
them slowly, the undisturbed forest fragments support more abundance of
endemics than man-modified habitats support commensals; perhaps an indication of
depletion of resources for small mammals in general.
Correct identification of taxa is
extremely important while understanding species compositions, richness,
diversity indices, evenness, ecology and community structure. Small mammals are very poorly understood due
to limited approaches to trapping methods. Much of our knowledge comes from morphological and morphometrics as
studied earlier by taxonomists. Relative
to location specimens show variations, which has prompted taxonomists to
identify populations as unique taxa. While this may cause an increase in taxonomic units, clubbing
ecologically distinct taxa does not serve the objectives of the study or
purposes of understanding community ecology. It is therefore important to assign taxa unique identities and thereby
the community ecology. Community studies
with poorly identified taxa make them less applicable in the long run.
Behavioural observation is a key to
taxonomic identification apart from morphology and morphometrics. In rodents and insectivores, conspecifics
closely resemble which makes identification difficult — the three Rattusspp., the two Mus spp., the two Suncus spp. are case in
point. Morphological characters help in
initial identification, but we learnt in our trapping and identification
efforts that observing individuals during handling and some individuals in
captivity provided clues to better identification. Identification, behavioural observations,
morphology and morphometrics of non-volant small mammals of Coorg from our study
will soon be published separately (Molur et al. in prep.).
The dominance of the white-bellied form
of Rattus rattus in the semi-evergreen forests of Mudumalai (Venkatraman
et al. 2005), montane evergreen forests of Nilgiris (Shanker 2001, 2003),
tropical rainforests of Anamalais (Prabhakar 1998), and middle elevation
evergreen forests of the Anamalais (Chandrashekar-Rao & Sunquist 1996),
while in our study the white-bellied form of Rattus rattus was dominant
only in human habitations and bamboo. In
one highly disturbed forest fragment near Ponnampet, with heavy logging and
lopping of trees and higher density of bamboos, we recorded only the
white-bellied form. In all other forest
fragments with no or little human interference, we trapped only the white-bellied
endemic canopy rat, R. satarae. We trapped P. lasiurus only in an undisturbed riverine forest
patch contiguous with the Brahmagiri Wildlife Sanctuary forests, while we did
not catch a single individual in any of the other forest fragments and plantations
with native and contiguous canopy. Our
study supports Prabhakar’s (1998) finding of P. lasiurus in only forest
fragments larger than 16ha in the Anamalais suggesting the importance of large
tracts of undisturbed forests for this species. Small islands of forests or sacred groves amidst plantations only
support R. satarae, but not P. lasiurus or Ratufa indica,
an indicator of the affects of changes in land use can have on endemic rodents
in the Western Ghats.
A structural change to vegetation not
only affects endemic species composition, but also tends to favour invasions by
commensal species increasing competition (Kumar et al. 2002). The total displacement of R. sataraeby R. wroughtoni in a disturbed sacred grove in southern Coorg suggests
change in quality of habitat and canopy structure negatively affecting the
endemic species. Similarly, displacement
of the forest shrew S. niger by S. murinus, a widespread
commensal in forest fragments is an indicator of structural changes on the
forest floor affecting endemics. Coffee
and cardamom plantations with native vegetation do not support such specialized
endemics due to different practices such as trimming of canopy, lopping,
clearing understory, clearing vines and the use of persticides. Although species richness is high in modified
landscapes of Coorg, the composition is dominated by commensals that do not
occur in undisturbed forests.
Madromys blanfordi was reported in
moist deciduous forests and teak plantations of the Anamalais by
Chandrashekar-Rao & Sunquist (1996), in deciduous forests of Mudumalai by
Venkatraman et al. (2005), in rainforest fragments of Indira Gandhi Wildlife
Sanctuary by Prabhakar (1998), and in montane forest of the Nilgiris by Shanker
(2003). However, we did not trap this
species in any habitat in Coorg, perhaps an indication of the effects of
changes in land use on the species.
This
study is a first step in understanding species composition of non-volant small
mammals in an extremely fast changing landscape of Coorg in the Western
Ghats. Since trends in plantation
practices are in a constant flux, endemics of Coorg face greater threats and
higher risks of extinction locally. Cardamom plantations which have the best available near natural
vegetation with contiguous canopy are threatened from over use of pesticides
and the changing mindset of planters to plant sun-loving varieties, which
result in fauna in canopies getting affected as well as the loss of old growth
trees, respectively. Continuous lopping
of branches of shade trees and replacement of native shade trees with exotic
trees such as casuarina and silver oak in coffee plantations cause grievous
damage to faunal species composition. The recent trend in clear felling coffee plantations for ginger
cultivation only encourages spread of commensals while effectively eliminating
endemic small mammals. While
conventional and systematic studies are needed to understand small mammal
community structure, rapid assessments and immediate conservation action are
required to stem the speed of loss of vegetation and changes in land use to
help prevent local extinctions and the increase in risks to endemics in the
Western Ghats.
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