Recent
records of snakes (Squamata: Serpentes) from Nicobar Islands, India
S. Harikrishnan 1,
B.C. Choudhary 1 & Karthikeyan Vasudevan 2
Wildlife Institute of India, P. O.
Box # 18, Dehra Dun, Uttarakhand, 248001, India.
Email: 2 karthik@wii.gov.in
(corresponding author)
Date
of publication (online): 26 October 2010
Date
of publication (print): 26 October 2010
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: Gernot Vogel
Manuscript
details:
Ms # o2314
Received 16
September 2009
Final revised
received 29 July 2010
Finally
accepted 15 September 2010
Citation: Harikrishnan, S., B.C. Choudhary & K.
Vasudevan (2010). Recent records of snakes (Squamata:
Serpentes) from Nicobar Islands, India. Journal of Threatened Taxa 2(11): 1297-1300.
Copyright: © S. Harikrishnan, B.C. Choudhary &
Karthikeyan Vasudevan 2010. Creative Commons Attribution 3.0
Unported License. JoTT allows unrestricted use of this article in any
medium for non-profit purposes, reproduction and distribution by providing
adequate credit to the authors and the source of publication.
Acknowledgements:This work was carried out with
support from Wildlife Institute of India grants-in-aid for research. The
Andaman and Nicobar Forest Department is thanked for permissions and logistic
help extended during the survey. We thank Andaman Nicobar Environmental Team
(ANET) for logistic support in Andamans. Indraneil Das and Gernot Vogel
commented on the identity of species and it helped us immensely. We thank the
staff of ZSI Port Blari for their support and encouragement.
The Andaman and Nicobar Islands have a fauna
that shows distinct affinities towards the fauna of South East Asia (Smith
1940; Das 1999). Within these
islands, the fauna of the Nicobar group of islands is derived from the Sundaic
fauna, unlike the Andaman group of islands whose fauna shows affinities with
the Indo-Malayan region (Das 1999). The distinctiveness of the fauna of the two groups of islands is
maintained by the ocean barrier at the 10 degreechannel (Das 1999). Several genera
and species of reptiles and amphibians are common to the Sundaic region and the
Nicobar Islands but are not found in the Andaman Islands (e.g. Bronchocela spp., Hylarana
nicobariensis, Hylarana chalconota etc.). Nineteen species of non-marine snakes
have been reported from the Nicobar Islands (Vijayakumar & David 2006;
Harikrishnan et al. 2010). Two
species of wolf snakes of the genus Lycodon Boie, 1826 are known from the Andaman and
Nicobar Islands. Lycodon capucinus Boie, 1827 often considered as a subspecies ofLycodon aulicus (Linnaeus, 1758) occurs on the Andaman
Islands, while Lycodon
tiwarii Biswas &
Sanyal, 1965 occurs on the Nicobar Islands (Harikrishnan et al. 2010). However, according to the original
description, the type of the latter originated in Andaman (Biswas & Sanyal
1965). The southern group of islands in the Nicobar that include the Great
Nicobar and the Little Nicobar were not known to harbor any species of wolf
snake. On 20 June 2008, we came
across a wolf snake in the Great Nicobar Biosphere Reserve, which we identified
as Lycodon subcinctus Boie, 1827 based on published keys by Smith
(1943) and Lanza (1999). Since this is the first specimen of this species from
the Nicobar Islands, we provide a short description of the specimen.
Lycodon subcinctus Boie, 1827
Snout broadly rounded and not depressed (Image
1). The rostral was wider than
long; posterior nasal much longer than anterior, and it was in broad contact
with prefrontal. Thus, it widely
separated the loreal from internasal. The prefrontals were large, more than twice as long as internasals and
were in contact with the eyes; preoculars were absent, and the loreal was in
broad contact with the eyes (Image 2). Frontal was longer than its distance from the snout tip. Supraoculars
were narrower than frontal and the parietals were almost twice as long as the
frontal. There were two
postoculars on either side of the head among which upper one was larger and was
in contact with anterior temporal. A single anterior temporal and two posterior temporals were present
among which the anterior was much larger than the posterior one. There were eight supralabials among
which 1st and 2nd touched the posterior nasal, 3rdtouched loreal, 3rd to 5th touched the eye, 6thin contact with lower postocular and anterior temporal, and 7th in
contact with anterior temporal and posterior lower temporal. The mental was small and
subtriangular. There were nine
infralabials, among which the first pair was in contact with each other. The first four infralabials were in
contact with anterior genial, while 4th and 5thinfralabials were in contact with the posterior genial. The 5th infralabial was the
largest. The genials were of
almost equal length with anterior pair broader than posterior pair. The body scales, counted at one head
length behind the head, at mid-body and one head length before vent, were in
17:17:15 rows, with those on the posterior half of the body weakly keeled.
There were 223 ventrals (counted according to Dowling 1951)
which were angular laterally. The anal was divided and there were 94 divided subcaudals. The subcaudal count is slightly higher
than that reported for L.
subcinctus so far (range
60-90) (Lanza 1999). The high
ventral and subcaudal count place this individual in the nominate subspecies Lycodon subcinctus subcinctus Boie, 1827 (Lanza 1999). The specimen measured 660mm in
snout-vent length and the tail length was 180mm.
The head was very dark brown above with a
slightly lighter mark near the occiput. The body was grayish brown on sides with this colour extending to the
part of ventrals outside the lateral notch. There were no bands on the body
(Image 1). The supralabials were
off white with black spots. The
ventrals and subcaudals were grey with off white edges while the lower jaw and
throat was white in colour.
The snake was found at 1900hr near the edge of
a stream in a rainforest in Great Nicobar Biosphere Reserve, approximately 1km
from Govind Nagar, at the 10km point, along the East-West road. It was fast and active, and shook its
tail from side to side when it was cornered. The snake was preserved in rectified spirit and deposited at
ZSI, Port Blair, Andaman and Nicobar Islands (Catalogue # 10643).
Lycodon tiwarii Biswas & Sanyal, 1965
This snake was described from Mayabunder in
North Andaman (Biswas & Sanyal 1965). The paratype of the species is suspected to originate from Car Nicobar,
based on the information that it was donated by the Government Hospital, Car
Nicobar (Biswas & Sanyal 1965). Das (1999) considered this species to be restricted to Andaman
Islands. Vijayakumar & David
(2006) recorded this species from six islands in Nancowry group of islands in
central Nicobar. The paratype
remains the only specimen collected from Car Nicobar whichis the northernmost island in Nicobar archipelago. During our survey in April 2008, we encountered two
individuals of this species on Car Nicobar (Image 3). The first individual, found on 16 April
2008, was killed by local people, and the examination of the stomach
revealed a freshly ingested Gliding Gecko Ptychozoon nicobarensisDas & Vijayakumar, 2009
measuring 80mm in snout-vent length. The snake itself measured 559mm in snout-vent length and 155mm in tail
length. The second individual was
found coiled up in a Pandanus leaf at 1700hr on 21 April 2008. This individual measured 854 mm in
snout-vent length and 179mm in tail length. In Car Nicobar, this snake is referred to as kulinga and gliding gecko as katamaey.
Coelognathus sp. from Great Nicobar Biosphere Reserve
Daniels & David (1996) reported the
presence of Black-tailed Trinket Coelognathus
flavolineatus (Schlegel, 1837)
on Great Nicobar. Vijayakumar
& David (2006) excluded this species from their checklist owing to the lack
of a voucher specimen. We had a
sighting of a large and dark colored Colubrid snake on Great Nicobar, in the
same area where the Malayan Wolfsnake Lycodon
subcinctus subcinctusBoie, 1827 was found. It was found
on 29 May 2008 at 1600hr, moving along the side of the road, when it was raining. We did not collect this snake; owing to
the lack of a voucher specimen and lack of information on taxonomy of species
belonging to this genus from the Sunda region, we refrain from assigning it a
specific name. We hope that our
description of the species will help in identifying it. We tentatively allocate this snake to
the genus Coelognathus Fitzinger, 1843, which was resurrected by
Helfenberger (2001) based on visceral organ topography, vertebral
characteristics and allozyme variations. The genus cannot be diagnosed based entirely on external morphology
(Helfenberger in Schleich & Kästle 2002). It was allocated to this genus because of the resemblance of
this snake to Coelognathus
flavolineatus (Schlegel, 1837)
in general pholidosis, particularly the ventral and subcaudal counts, and the
mid-body scale rows. There are
several other characters that differed in this snake from Coelognathus flavolineatus (Schlegel, 1837) and they are discussed below.
Description of the meristic characters and
colour of this individual are as follows: Prefrontals were about twice as long as internasals. The frontal was a little longer than prefrontals. The supraoculars were slightly narrower
than frontal. Parietals were
broader and longer than the frontal. There were nine supralabials on either side, with 5th and 6thin contact with the eye. 8thsupralabial was the largest. There
were 11 infralabials on either side, among which 1st-5th were in contact with anterior genial and 7th was the
largest. Anterior genials were
shorter than posterior genials. There were two preoculars, of which upper one was larger. There was a small pre-subocular also on
both sides of the head. The loreal
was square and was in contact with both the upper and lower preoculars. There
were two post oculars, among which upper one was larger. There were two anterior and three
posterior temporal shields. The
anterior pair of temporal was longer than the posterior pair. The anterior lower temporal was in contact
with 6th to 8th supralabials. Body scales were in
21:19:17 rows at one head length behind the head at mid-body and one head
length before vent respectively. All except the outer 1-2 rows of scales on the body were strongly keeled. The keels were most prominent on
posterior half of the body and tail. There were 209 ventrals, with a lateral keel. Subcaudals numbered 75, and all were divided (tail
incomplete). The anal shield was
undivided. The specimen measured
1195mm snout-vent length, and 280mm incomplete tail length. The head was light brown on top, while
the occipital region was much darker brown. The anterior dorsal body color was dark grey, which became
paler and more pinkish on sides of the body. Posterior body and tail were black. An oblique dark bar on either side of
the neck was visible faintly. Black and white inter-scale colors were visible when the snake inflated
the body in defense. The ventrals were yellowish white with grey edges.
This snake differed from Coelognathus
flavolineatus (Schlegel, 1837), that is the only other species of Coelognathus known to exist in Andaman
and Nicobar Islands, in having two pre-oculars (one in C. flavolineatus), presence of a
pre-subocular (absent in C. flavolineatus), two supralabials in contact with the eye (three in C. flavolineatus), 8thsupralabial largest (9th largest in C. flavolineatus). This specimen differed
from Coelognathus subradiata (Schlegel, 1837) and Coelognathus
radiata (Boie, 1827) in its low ventral counts (209 vs. 226-248 in C. subradiata, 222-250 in C. radiata). It differed from Ceolognathus
erythrurus (Duméril, Bibron & Duméril, 1854) in having 19 scale
rows at mid-body (21 in C. erythrurus). Finally,
it differed from Coelognathus helena (Daudin, 1803) in having 19 scale rows at mid-body as
against 25-29 in C. helena. This comparison is based
on published keys (de Rooij 1917; Smith 1943; Helfenberger in Schleich & Kästle
2002) as well as a live specimen of C. flavolineatus from South Andaman. As is evident from this brief comparison, the specimen
cannot be allocated with confidence to any of these species. Collection of a voucher specimen is
required to determine the taxonomic status of this species.
This snake was very slow
in movements, coiled itself in a defensive position and inflated the neck and
fore-body, in a manner typical of many other Coelognathus sp. when approached closely (Image 4). According to the information provided
by a local person, this snake is found in thick vegetation, but is not common.
The addition of Lycodon subcinctus
subcinctus Boie, 1827 and the Coelognathus sp. to the fauna brings the total number of snake species
known from Nicobar Islands to 21. Vijayakumar & David (2006) reported on unconfirmed sightings of Cantoria sp. from these islands. Also, many other species of snakes are
known from single records or original descriptions. Examples include Boiga cyanea (Duméril, Bibron & Duméril, 1854) (Das & Chanda
1994) and Amphiesma nicobarense(Sclater, 1891). It is likely that many
reptile species await documentation in these islands.
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