Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 September 2021 | 13(11): 19652–19656
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.7051.13.11.19652-19656
#7051 | Received 05 January 2021 | Final
received 12 April 2021 | Finally accepted 18 August 2021
First record of the Eastern Cat
Snake Boiga gocool
(Gray, 1835) (Squamata: Colubridae)
from Tripura, India
Sumit Nath 1, Biswajit
Singh 2, Chiranjib Debnath 3 &
Joydeb Majumder 4
1,3 Herpetofauna Conservation and
Research Division, Wild Tripura Foundation, Dhaleshwar,
Road No. 13, Agartala, Tripura, India.
2 Department of Ecology and
Environmental Science, Assam University, Silchar,
Assam 788011, India.
4 Department of Zoology, Ecology
& Biosystematics Laboratory, Tripura University, Tripura 799022, India.
1 nathsumit389@gmail.com
(corresponding author), 2 biswajitsingh87@gmail.com, 3 chiranjibbiologist@gmail.com,
4 jmtugemo@gmail.com
Editor: S.R. Ganesh, Chennai Snake Park,
Chennai, India. Date of publication: 26 September 2021
(online & print)
Citation: Nath, S., B. Singh, C. Debnath
& J. Majumder (2021). First record of the Eastern Cat
Snake Boiga gocool
(Gray, 1835) (Squamata: Colubridae)
from Tripura, India. Journal of Threatened Taxa 13(11): 19652–19656. https://doi.org/10.11609/jott.7051.13.11.19652-19656
Copyright: © Nath et al. 2021. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: Wild Tripura
Foundation.
Competing interests: The authors
declare no competing interests.
Acknowledgements: Authors express their earnest
thanks to Mr. Pallab Chakraborty, director of Sepahijala Zoological Park, Sepahijala,
Tripura, India for helping in identification of the species and Wild Tripura
Foundation, Tripura, India for help to study the herpetofaunal
diversity of Tripura.
Northeastern India has a rich herpetofaunal diversity, with 102 species of snakes,
represented by six families comprising
42 genera (Ahmed et al.
2009; Aengals et al. 2018) with some new snake genera
and species recently discovered in, e.g., Blythia
hmuifang, Pareas modestus, Gongylosoma
scriptum, Smithophis atemporalis, Hebius lacrima, Trimeresurus salazar, Trachischium aptei, Trimeresurus arunachalensis, Smithophis arunachalensis, Hebius pealii (Vogel et al. 2017, 2020; Lalremsanga
2018; Bhosale et al. 2019; Captain 2019; Giri et al.
2019; Purkayastha & David 2019; Das et al. 2020;
Mirza et al. 2020). Tripura is a landlocked, small, hilly state surrounded by
Assam & Mizoram of India and Bangladesh on three sides (Image 1). So far,
21 species of snakes under 19 genera and six families have been reported from
the state (Majumder 2012; Purkayastha et al. 2020). Earlier, only one species of the
genus Boiga, B. ochracea
was recorded from the state (Majumder et al. 2012; Purkayastha
et al. 2020).
Boiga gocool (Gray, 1835) is a nocturnal,
arboreal, mildly venomous snake that occurs in tropical semi-evergreen and
degraded forests, tall grasslands, and tea gardens at lower elevations of
50–1,000 m (Das et al. 2010; Wallach et al. 2014). It feeds mainly on lizards but sometimes also
on small birds and mammals. Boiga gocool is poorly known, has a narrow distribution,
and is thus rarely reported in regional inventory reports with only a few
preserved specimens in scientific collections (Das et al. 2010). This is a
southern Asian species having definite distribution records from northern and
eastern India, Bangladesh, and Bhutan (Ahsan et al. 2015; Das et al. 2016). Of
late, a few records of this species were reported from many other places. In
India, B. gocool is reported from
Assam- Manas National Park, Guwahati (Purkayastha et al. 2011), Kaziranga
National Park (Das et al. 2007), Arunachal Pradesh, Manipur, Meghalaya,
Nagaland (Das et al. 2007; Bhupathy et al. 2013),
Sikkim (Chettri et al. 2011), West Bengal (Das et al. 2007), northern Odisha (Mohalik et al. 2020), and Uttar Pradesh (Choure et al. 2020). It has been listed as Schedule IV
species under the Indian Wildlife (Protection) Act, 1972 (Ahmed et al. 2009)
whereas under IUCN Red List category, it stands as ‘Not Evaluated’.
In this note, we report our
sighting of B. gocool in Tripura state. The
current survey site is situated within the Khowai
district of Tripura (24.064N & 91.596E; 129m), the forest patch of the
survey area was primarily mixed moist
deciduous type (Choudhary et al. 2019) having tree species like Tectona grandis, Shorea robusta, Dalbergia sissoo, Bombax
ceiba, Phayllanthus emblica,
and Mangifera indica
spread over an undulating terrain with moderate canopy cover.
The observation made by us was
based on opportunistic sightings in the field. On 12 July 2020, during a field
visit to Khowai, we noticed
a snake passing by near the Khowai river bridge at
evening 1539 h. The snake was restrained using a snake hook with utmost safety
for making morphological observations and measurements. Photographs were taken
using DSLR camera. The length of the individual from snout to vent (SVL) was
measured by measuring tape. Gender was confirmed by observing everted hemipenis of the individual and subsequently, the snake was
released where it was initially observed.
The recorded individual showed
morphological characters as follows: triangular head, distinctly broader than
the neck; dorso-laterally compressed body consisting
of yellowish-brown dorsal colour with paired
dorsolateral series of 45 black vertical Y-shaped markings on the either side
which was separated from one another only by the light yellowish vertebral
scale row; black markings edged with white; anterior-most six Y-shaped markings
fused to form small black lines; markings broken down to small black spots
posteriorly; tail with a few small irregular brownish spots, but without
markings towards the tip; a large dark brownish arrow-shaped mark with darker
edges begins at the posterior part of the inter-nasals, covering the top of the
head; an arrow shaped mark followed by black, round spot on nape (Image 2a); a
black postocular stripe extending from jaw angle to
neck, ending at lower 3rd dorsal scale row; supra-labials and
infra-labials white, with small black markings on sutures; pupil black with
yellow iris; ventral yellowish-white with small black spots at the lateral
edges (Image 2b). The gender of the individual was confirmed as male, by
observing everted hemipenis. The length of the
individual from snout to vent (SVL) measured 652 mm and tail length (TL) was
165 mm. Comparing the above data with the identification keys and descriptions
specified in standard literature (Whitaker & Captain 2008; Ahmed et al.
2009; Das et al. 2010; Mohalik et al. 2020) the snake
was positively identified as Boiga gocool.
Comparing the morphological
characteristics between the known Boiga
species in northeastern India, it is evident that the dorsolateral series of
45–50 dark brownish and whitish edged Y or T shaped marks, divided by distinct
light vertebral scale row and a narrow black diamond or circular shaped nuchal
dot, that never reaches to the sides of the body were major distinguishing
characteristics of B. gocool (Table 1). In the
past, much confusion existed regarding distinguishing between B. gocool and its closely related and one of the most
widely distributed yet poorly studied congener in Indian subcontinent, B. t.
trigonata (Das et al. 2010). Regardless, B. gocool has a lot in common with B. t. trigonata in terms of habits, body proportions, and
skin colour, but gocool
can be differentiated from trigonata by
strongly enlarged vertebral scales and an entirely distinct head and dorsal
body colour pattern, and dorsolateral series of 45–50
dark brownish and whitish edged Y-shaped marks which are prominently divided by
a light vertebral scale row; whereas B. trigonata
has yellow to whitish, dark edged, angular markings, with irregular branching
across the vertebral scale row, often connected in a zigzag manner. The sole
congener of B. gocool recorded from the state
was B. ochracea (Majumder et al. 2012; Purkayastha et al. 2020) which can be readily distinguished
without confusion from B. gocool by its patternless or indistinct dark transverse dorsolateral
bands on coral red, reddish- or yellowish-brown dorsal body (Table 1).
With the centre
of radiation of B. gocool lying in the plains
and low hills of north and south of the Brahmaputra valley, Assam, (Das et al.
2010), recent records of B. gocool from Odisha
(Mohalik et al. 2020) and Uttar Pradesh (Choure et al. 2020), extend its known distribution range
further to the south and west, respectively. The current record of B. gocool from Tripura eventually fills the void in its
northeastern Indian distribution. The present survey site is about 40 km
north-east from Agartala, the state capital and about 35 km south to the
nearest previously recorded locality for the species from Lawachara
National Park, Sylhet District, Bangladesh (Rahman et al. 2013). The nearest
occurrence of B. gocool from the present
survey site, within northeastern India,
is that of Mizoram (Lalremsanga & Lalronunga 2017; Choure et al.
2020). Despite being situated in the Indo-Burma biodiversity hotspot, Tripura
is rather poorly studied from the herpetofauna assessment viewpoint. Most of
the herpetofaunal studies were limited to a few taxa
and locations of the state (Majumder et al. 2012; Purkayastha
et al. 2020). Before the current record, only one species of the genus Boiga (B. ochracea)
was reported from Tripura, whereas eight representatives of the genus have been
reported and found to be occurring in northeastern India, partly sympatric with
B. gocool (Table 1). Hence, the first record
of B. gocool from this state will contribute
towards updating the checklist of the herpetofauna of Tripura. Future studies
on the genus Boiga and other snake species
sympatric with B. gocool throughout the state
is much needed.
Table 1. Morphological
comparisons of body (dorsal and ventral), head and tail morphology between B.
gocool and other congeneric species from the
Indo-Burma hotspot.
|
Species |
Dorsal body |
Ventral body |
Head and tail |
Distribution in Indo-Burma |
References |
|
gocool |
Dorsal colour yellowish- brown;
dorsolateral series of 45–50 dark brownish and whitish edged Y or T shaped
marks. |
Light yellowish- brown ventral
colour with small dark brown margins or pattern less. |
Head noticeably larger than
neck; wide eye with vertical pupil, long tail. |
Arunachal Pradesh, Assam,
Nagaland, Manipur, Mizoram, Bhutan, and Bangladesh. |
Das et al. 2010; Das et al. 2016; Lalremsanga & Lalronunga 2017; Whitaker
& Captain 2008 |
|
cyanea |
Dorsal colour uniform green or
greyish- or bluish-green; black Interscale colour,
same colour on the head and few dorsal scales. |
Greenish- or yellowish-white
belly; subcaudal scales are paired in a zig-zag pattern. |
Head triangular with rounded
tip, distinctly wider than body. Top of the head is normally same colour as
the dorsal or has a brownish hue. Like other arboreal snakes, long thin tail
with pointed tip. |
Arunachal Pradesh, Assam,
Meghalaya, Mizoram, Sikkim, Bangladesh, and Bhutan. |
Das et al. 2010; Lalremsanga & Lalronunga 2017; Whitaker & Captain 2008 |
|
multifasciata |
Dorsal pattern made up of
narrow black irregular transverse bands separated by reddish-brown vertebral
scale lines. |
Ventral surface greyish- to
reddish-brown. |
Head wider than neck; large eye
has vertical pupil. Long tail. Two black lines run across the top of the
head; another runs down the neck, a black stripe runs behind the eye. |
Arunachal Pradesh and Sikkim. |
Tshewang, & Letro 2018; Das et al. 2010; Whitaker & Captain 2008 |
|
multomaculata |
Dorsal colour is greyish-brown
with dark brown markings, black edges, and brown; double series of
conspicuous spots present. |
Ventral colour is greyish-brown
or impure white, marked with brown spots. |
Head noticeably larger than
neck; eye with vertical pupil; long tail. |
Arunachal Pradesh, Assam,
Nagaland, and Bangladesh. |
Das et al. 2010; Whitaker &
Captain 2008 |
|
ochracea |
Dorsal body coral red, reddish-
or yellowish-brown. |
Scales on the anterior belly
are yellow, while those on the mid-body and tail tip are light brown. |
Head larger than neck; wide eye
with vertical pupil; tail long and thin. |
Sikkim, Assam, Tripura,
Mizoram, Bhutan, and Bangladesh. |
Das et al. 2010; Lalremsanga & Lalronunga 2017; Majumder et al. 2012; Whitaker & Captain 2008 |
|
quincunciata |
Fine dark brown spots and a
dark brown vertebral series make up the dorsal pattern. |
Outer edges of the ventral
surface are yellowish-white with white or brown spots |
Three longitudinal stripes on
the nape; head and neck distinct; body slender and elongated; eyes wide with
vertical pupil. |
Arunachal Pradesh, Assam,
Mizoram, and Bhutan. |
Chaida et al. 2020; Das et al. 2010; Lalremsanga & Lalronunga 2017 |
|
siamensis |
Dorsal body yellowish-brown;
many large black or dark brown oblique bands or V-shaped markings. |
Ventral surface yellowish- or
greyish-brown, with small dark brown spots present sometimes. |
Head wider than neck; large eye
has vertical pupil; tail long. |
Arunachal Pradesh, Assam,
Mizoram, Meghalaya, Sikkim, Nagaland, and Bangladesh. |
Das et al. 2010; Lalremsanga & Lalronunga 2017; Whitaker & Captain 2008 |
|
trigonata |
Dorsal colour brown or tan;
darker zigzag markings that are possibly connected. |
Underside of each belly scale
white or tan, small black spots on the outer edges. |
Head wider than neck; Large eye
with vertical pupil; tail long; distinct pale Y-shaped mark appears on top of
the head, which often black-edged. |
Sikkim. |
Das et al. 2010 |
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