Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 September 2018 | 10(10):
12328–12336
Species composition and abundance estimates of reptiles in selected
agroecosystems in southern Western Ghats, India
Abhirami Mini Jayakumar
1 & Paingamadathil Ommer Nameer 2
1,2 Centre for Wildlife Studies, College of
Forestry, Kerala Agricultural University, Thrissur,
Kerala 680656, India
1 abhirami.mj@gmail.com, 2 nameer.po@kau.in
(corresponding author)
doi: https://doi.org/10.11609/jott.3652.10.10.12328-12336 | ZooBank:
urn:lsid:zoobank.org:pub:860DCCC7-66AB-4A46-A362-5EC56D844488
Editor: Pritpal S. Soorae,
Environment Agency Abu Dhabii, United Arab Emirates. Date
of publication: 26 September 2018 (online & print)
Manuscript details: Ms
# 3652 | Received 14 July 2017 | Final received 02 August 2018 | Finally
accepted 12 September 2018
Citation: Jayakumar, A.M. & P.O. Nameer
(2018). Species composition and abundance
estimates of reptiles in selected agroecosystems in
southern Western Ghats, India. Journal of Threatened Taxa 10(10): 12328–12336; https://doi.org/10.11609/jott.3652.10.10.12328-12336
Copyright: © Jayakumar & 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.
Author Details: Abhirami M. Jayakumar is a PG research scholar, whose interest include taxonomy and ecology of reptiles of Western Ghats. P.O. Nameer is
a Professor and his research interest include the taxonomy, biogeography and ecology of the vertebrates except fishes.
Author Contribution: Both the authors contributed equally to the design of the study, field work, morphometric data collection,
analysis and manuscript preparation.
Acknowledgements: We thank Neelesh Dahanukar, IISER, Pune for his assistance with data analysis. Abhin M. Sunil, Bharath M. R., Habeel Sahal, Nibin
Antony K., Francis Scaria, Al Ameen
A., Sreekumar E. R., Prajeesh
P., Syamili M. S., Dilgith Surendran and Amal U. S. assisted
us with the field work. The Dean, College of Forestry,
Kerala Agricultural University is acknowledged for the encouragement and
support. We also thank the anonymous reviewers and the Subject Editor for their
critical comments.
Abstract: Species composition and abundance of
reptiles in selected agroecosystems in Thrissur plains, near Palghat
Gap, southern Western Ghats in India, was studied from January 2017 to May
2017. The agroecosystems
surveyed were coconut, cashew & rubber plantations, home garden, paddy
field, and botanical garden.
Time-constrained visual encounter surveys of a total effort of 360
man-hours were done in the field.
Coconut and cashew plantations reported the highest species richness
with 11 species each, while the highest number of sightings
(159) were recorded from botanical garden. Bronze Grass Skink Eutropis
macularia was the most abundant species in agroecosystems.
Correspondence analysis was done to compare the reptilian diversity in
the agroecosystems.
The reptile fauna of home garden and paddy field were found to be more
distinct than the rest of the agroecosystems. A total of 17 species of reptiles were
recorded during the study, thus highlighting the significance of agroecosystems in acting as important buffer landscapes for
reptiles.
Keywords: Cashew plantation, coconut plantation,
botanical garden, home garden, Important Bird Area, Kole
wetlands, paddy field, Ramsar site, rubber
plantation.
INTRODUCTION
Nearly
two-thirds of the terrestrial environment of the world is made up of managed
ecosystems with natural, undisturbed habitats accounting for only a meagre five
percentage. These managed ecosystems
include agricultural systems, forestry systems, and human settlements (Gamage et al. 2008).
Herpetofauna makes up 48% of the terrestrial
vertebrates that are threatened by agroforestry and forestry activities
(Palacios et al. 2013).
Despite the fact that herpetofauna makes up
half of vertebrate species, they are very much understudied in their response
to change in habitats from natural forests to plantations.
The review done by Palacios et al. (2013) on the herpetofauna
of agroecosystems on a global scale found just 27
studies pertaining to amphibians and reptiles.
Very few studies on the reptilian diversity of agroecosystems
have been done in southern India too.
Perhaps the only study on the reptiles of human-modified habitats is the
one by Venugopal (2010), who studied the agamids of human-modified habitats in the Western Ghats.
In a
time when more and more forest areas are being converted into plantations and
agricultural lands for meeting the growing needs of human populations, it is
important to evaluate the reptile diversity in these modified ecosystems. It is important to assess whether these agroecosystems are capable of supporting and sustaining reptile
biodiversity, particularly that of habitat specialists and endemic species.
STUDY AREA
The
study was conducted in selected agroecosystems in Thrissur District, southern Western Ghats, Kerala (10.53–10.550N & 76.27–76.280E,
20–70 m). The agroecosystems chosen included cashew, coconut & rubber
plantations, home garden, paddy field, and botanical garden (Fig. 1). The study area chosen mostly comes within the
main campus of Kerala Agricultural University in Kerala. The campus has a total area of 391.44ha and
is located very close to Peechi-Vazhani Wildlife
Sanctuary. The major habitats include
gardens, botanical gardens, plantations of rubber,
coconut, plantain & cocoa, and orchards of mango, jackfruit, sapota & guava.
The whole area must have been under forests about one and a half
centuries ago and was subsequently converted mostly into rubber
plantations. Later, in 1971, the land
was handed over to the Kerala Agricultural University (KAU), and the KAU
developed these areas into different land uses as explained above. The 14-year mean minimum temperature is 23.30C
and the 10-year mean maximum is 31.90C. The area receives southwest and northeast
monsoons, the greater portion of the rainfall, however, is received from the
southwest monsoon between June and September.
The mean annual rainfall is 2803.4mm.
The mean number of rainy days per year is 112 (Manohar
et al. 2017). The paddy field selected
was located at the Kole Wetlands in central Kerala,
which incidentally is a Ramsar site and an Important
Bird Area (IBA) (Islam & Rahmani 2004, 2008).
METHODS
The
method followed was time-constrained visual encounter survey of a two-hour
duration in each of the agroecosystems in the morning
(08:00–10:00 hr) and evening (19:00–21:00 hr). Each location
was covered on foot and whenever a species was sighted, observations such as
the name of the species, the number of sightings, time, and GPS location were
recorded following Ishwar et al. (2001). At each agroecosystem,
the survey was carried out for five days.
Thus, the total effort spent during the entire course of the study was 360 man -hours.
Additionally, micro-habitat parameters such as
canopy height, canopy cover, leaf litter depth, leaf litter cover, shrub cover,
herb cover, and number of fallen logs were recorded at each of the agroecosystems.
Litter depth was measured using a steel scale (Elora)
and canopy height was measured using Haga altimeter (Durga Enterprises).
The rest of the measurements were visually estimated (see Vasudevan et al. 2001; Kanagavel
et al. 2013). Weather data like maximum
temperature, minimum temperature, and relative humidity for the study period
was obtained from the Kerala Agricultural University Weather Station located in
Thrissur District, Kerala. The study was carried out from January to May
2017 in the pre-monsoon season.
For
confirming the identification of the species, the following literature were
consulted: Das (2002), Whitaker & Captain (2004), Mahony
(2011), Agarwal & Karanth
(2015), Agarwal et al. (2016), Lajmi
et al. (2016). The distribution range
of the species was verified using Ganesh et al. (2013) and Palot
(2016).
Statistical Analysis
Chi-square
analysis of association was performed to understand whether the reptile fauna
had a preference for any plantation types (coconut, cashew, rubber, home
gardens, botanical gardens, or paddy fields).
Patterns of relationship between species abundance across nine
environmental parameters (canopy cover, canopy height, litter depth, litter
cover, shrub cover, herb cover, maximum temperature, minimum temperature, and
relative humidity) in different plantation types were investigated using
canonical correspondence analysis (CCA), a multivariate constrained ordination
technique (Legendre & Legendre 1998).
A triplot of observations grouped for
plantation types, species, and eigenvectors of environmental variables was
plotted to understand the species distribution along the plantation types and
environmental variables. A scree plot of
eigenvalues and cumulative inertia explained by each canonical axes was plotted to understand the contribution of each
axes. The significance of the canonical
axes was tested using permutations test (Legendre et al. 2011). Statistical analysis was performed in PAST
3.19 (Hammer et al. 2001).
RESULTS AND
DISCUSSION
A total
of 594 sightings of 17 species (Table 1) was
encountered from the agroecosystems during the study
period, with an average pooled encounter rate of 1.27 reptiles/man-hour. The species richness was the highest in
coconut and cashew plantations, with 11 species each (Table 2; Images
1–14). The abundance of the reptiles,
however, was greatest in botanical gardens (159 sightings). Bronze Grass Skink Eutropis
macularia was the most
encountered species in the agroecosystems of Thrissur District with 220 sightings, followed by
(Murray’s) House Gecko Hemidactylus cf. murrayi totalling 87 sightings.
The
variation in the number of sightings of the reptiles between day and night are
given in Fig. 2. As expected, it can be
seen that most of the reptiles were more active during night hours. Out of the six species of geckos seen during
the study, all four species of Hemidactylus
geckos, as well as Cyrtodactylus
cf. collegalensis, were nocturnal in
habit. The Day Geckos Cnemaspis spp., however, as its common name suggests,
were observed mainly during morning hours.
Among skinks, Ristella cf. beddomii was primarily a nocturnal species, while Sphenomorphus dussumieri
was spotted only during day hours. Eutropis macularia,
E. carinata, and the agamid lizard Calotes versicolor
were observed during both morning and night hours. Calotes versicolor was observed to be sleeping when spotted
during night hours. All the seven
species of snakes observed were spotted during night hours (Fig. 2).
There
was a significant association between plantation types and abundance of
different reptile species (chi square = 1006.3, df =
80, P < 0.0001), indicating that the reptile fauna had a differential
preference for the plantation type. The
complex pattern of reptile species distribution across the plantation types and
environmental variables are depicted in the CCA triplot
(Fig. 3). The first two CCA axes were
significant (permutations 999, trace = 1.047, P = 0.001; canonical axis 1, eigen value = 0.4199, P = 0.001; canonical axis 2,
eigenvalue = 0.2819, P = 0.001) and together they explained 67% total inertia
in the data. Both species composition
and environmental parameters of the different plantation types were different
with no overlap for paddy fields, indicating that paddy fields are not only
distinctly different in the environmental parameters but has a different
reptile fauna. Xenochrophis
piscator was unique to the paddy field habitat
while Lycodon aulicus
was more abundant in the paddy field as compared to other habitats and both
these factors could be correlated to the relatively higher humidity and
temperature of paddy field habitats and lower canopy cover, canopy height,
litter depth, litter cover, shrub cover, and herb cover (Fig. 3). In general, species such as Boiga beddomei, Bungarus caeruleus,
Calotes versicolor,
Coelognathus helena,
Hemidactylus frenatus,
H. cf. murrayi, H. triedrus, Sphenomorphus
dussumieri, Lycodon
aulicus, and Xenochrophis
piscator preferred relatively higher humidity and
temperature and lower canopy cover, canopy height, litter depth, litter cover,
shrub cover, and herb cover. As a
result, these species mainly favoured home gardens and paddy fields in Kole Wetlands, followed by cashew and coconut plantations
and, rarely, rubber plantations or botanical gardens. On the other hand, Ahaetulla
cf. nasuta, Cnemaspis
sp., Cryodactylus collegalensis,
Eutropis macularia,
Eutropis carinata,
Oligodon taeniolatus,
and Ristella cf. beddomii
preferred higher canopy cover, canopy height, litter depth, litter cover, shrub
cover, and herb cover and favoured rubber plantations and botanical gardens,
followed by cashew and coconut plantations (Fig. 3).
While
this is a preliminary, pooled analysis consisting of resource use frequencies
of both active and dormant sightings, it gives at least a preliminary picture
of probable impacts on resultant species records. We mention this with a caution that more
studies with better sample size and discerning active and dormant sightings are
needed to fully understand the impacts of these abiotic variables on species
composition and assemblage structure. We
believe that our work will pave the way for future studies to take a deeper
look into this subject (also see Vijayakumar et al.
2006).
Palacios
et al. (2013), who reviewed studies on the herpetofauna
in human-modified habitats across the world, found that in 81% of the cases
plantations supported more herpetofauna than natural
forests. They also found that
human-modified habitats support even some endemic species in agroecosystems. Two
species of reptiles endemic to the Western Ghats, Ristella
cf. beddomii and Sphenomorphus
dussumieri, were recorded from the agroecosystems of central Kerala. The present sighting of the Ristella cf. beddomii
from the agroecosystem at an elevation of 50m is
lower than the known altitude range of 400–1300 m (Srinivasulu
et al. 2014) of this species.
Apart
from addressing reptile conservation in managed landscapes, our study also
fills in a major gap in herpetological studies in southern India – their
community assemblage structure. Very few
studies have elaborated on this topic.
Studies from Western Ghats rainforests (Inger
et al. 1987), the Western Ghats dry forests (Vijayakumar
et al. 2006), Eastern Ghats wet forests (Ganesh & Arumugam
2015; & Ramesh & Arumugam 2016), and the
Coromandel coastal plains scrub forests (Ramesh et al. 2013) are
available. The current paper provides a
first-hand data on reptile assemblage structure from a central Kerala plains
site, that too from the little-studied Palghat Gap
region.
This
documentation is important as it highlights the significance of agroecosystems in conserving and maintaining the reptilian
fauna of the region, including some of the Western Ghats endemic species.
Table 1. Reptiles of selected agroecosystems
in Thrissur District
|
Common name |
Scientific name |
Family |
IUCN status |
Image |
1 |
(Murray’s) House Gecko |
Hemidactylus cf. murrayi |
Gekkonidae |
NE |
Image 1 |
2 |
Common House Gecko |
Hemidactylus frenatus |
Gekkonidae |
LC |
Images 2 & 3 |
3 |
Termite Hill Gecko |
Hemidactylus triedrus |
Gekkonidae |
NE |
Image 4 |
4 |
Day Gecko |
Cnemaspis cf. gracilis |
Gekkonidae |
|
Images 5 & 6 |
5 |
Kollegal Ground Gecko |
Cyrtodactylus collegalensis |
Gekkonidae |
NE |
Image 7 |
6 |
Dussumier’s Litter Skink* |
Sphenomorphus dussumieri |
Scincidae |
LC |
Image 8 |
7 |
Bronze Grass Skink |
Eutropis macularia |
Scincidae |
NE |
Image 9 |
8 |
Common Keeled Skink |
Eutropis carinata |
Scincidae |
LC |
Image 10 |
9 |
(Beddome’s) Cat Skink* |
Ristella cf. beddomii |
Scincidae |
LC |
Image 11 |
10 |
Oriental Garden Lizard |
Calotes versicolor |
Agamidae |
NE |
Image 12 |
11 |
Common Indian Krait |
Bungarus caeruleus |
Elapidae |
NE |
|
12 |
Beddome’s Cat Snake |
Boiga beddomei |
Colubridae |
LC |
|
13 |
Common Wolf Snake |
Lycodon aulicus |
Colubridae |
NE |
|
14 |
Common Trinket Snake |
Coelognathus helena |
Colubridae |
NE |
|
15 |
(Common) Vine Snake |
Ahaetulla cf. nasuta |
Colubridae |
NE |
Image 14 |
16 |
Russell’s Kukri Snake |
Oligodon taeniolatus |
Colubridae |
LC |
Image 13 |
17 |
Checkered Keelback |
Xenochrophis piscator |
Natricidae |
NE |
|
Table 2. Species diversity and abundance of reptiles in selected
agroecosystems in Thrissur
District
|
Species |
Coconut Plantation |
Cashew Plantation |
Rubber Plantation |
Home garden |
Botanical Garden |
Paddy field |
Total |
Number of sightings |
||||||||
1 |
Hemidactylus cf. murrayi |
47 |
20 |
3 |
2 |
10 |
0 |
82 |
2 |
Hemidactylus frenatus |
40 |
6 |
16 |
4 |
3 |
0 |
69 |
4 |
Hemidactylus triedrus |
0 |
2 |
0 |
0 |
0 |
0 |
2 |
5 |
Cnemaspis spp. |
10 |
1 |
8 |
3 |
19 |
0 |
41 |
6 |
Cryodactylus collegalensis |
7 |
6 |
18 |
2 |
11 |
0 |
44 |
7 |
Sphenomorphus dussumieri |
0 |
0 |
0 |
13 |
0 |
0 |
13 |
8 |
Eutropis macularia |
21 |
45 |
82 |
2 |
70 |
0 |
220 |
9 |
Eutropis carinata |
1 |
9 |
0 |
0 |
14 |
0 |
24 |
10 |
Ristella cf. beddomii |
0 |
11 |
5 |
0 |
28 |
0 |
44 |
11 |
Calotes versicolor |
16 |
11 |
9 |
3 |
3 |
0 |
42 |
12 |
Bungarus caeruleus |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
13 |
Boiga beddomei |
1 |
0 |
1 |
0 |
0 |
0 |
2 |
14 |
Lycodon aulicus |
1 |
1 |
0 |
0 |
0 |
2 |
4 |
15 |
Coelognathus helena |
1 |
0 |
0 |
0 |
0 |
0 |
1 |
16 |
Ahaetulla cf. nasuta |
0 |
0 |
1 |
0 |
0 |
0 |
1 |
17 |
Oligodon taeniolatus |
0 |
0 |
0 |
0 |
0 |
3 |
1 |
18 |
Xenochrophis piscator |
0 |
0 |
0 |
0 |
1 |
0 |
3 |
|
Total |
145 |
112 |
143 |
30 |
159 |
5 |
594 |
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