Journal of Threatened Taxa | | 26 September 2021 | 13(11): 19652–19656


ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)

#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 (corresponding author), 2, 3, 4




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.


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.


Dorsal body

Ventral body

Head and tail

Distribution in Indo-Burma



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



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


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


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


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


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


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


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.


Das et al. 2010



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