Journal of Threatened Taxa | | 26 May 2021 | 13(6): 18544–18550


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

#5412 | Received 16 December 2019 | Final received 09 March 2021 | Finally accepted 27 March 2021



Conservation breeding of Northern River Terrapin Batagur baska (Gray, 1830) in Sundarban Tiger Reserve, India


Nilanjan Mallick 1, Shailendra Singh 2, Dibyadeep Chatterjee 3  & Souritra Sharma4


1,3,4 Sundarban Tiger Reserve, Canning Town, South 24 Parganas, West Bengal 743329, India.

2 Turtle Survival Alliance, India- D1/317, Sector F, Jankipurum, Lucknow, Uttar Pradesh 226021, India.

1, 2 (corresponding author), 3, 4




Editor: L.A.K. Singh, Bhubaneswar, Odisha, India.           Date of publication: 26 May 2021 (online & print)


Citation: Mallick, N., S. Singh, D. Chatterjee & S. Sharma (2021). Conservation breeding of Northern River Terrapin Batagur baska (Gray, 1830) in Sundarban Tiger Reserve, India. Journal of Threatened Taxa 13(6): 18544–18550.


Copyright: © Mallick 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: West Bengal Forest Department; West Bengal State Zoo Authority; IUCN Save our Species (SOS) 2012A-031 (2014); Ocean Park Conservation Fund, Hong Kong- OPCFHK_RB02_1516 (2015–2016); People Trust for Endangered Species- (2015-2016); Auckland Zoo (2014–2015); Alan and Patricia Koval Foundation.


Competing interests: The authors declare no competing interests.


Author details: Mr. Nilanjan Mallick is current Additional Principal Chief Conservator of Forests and Chief Conservator of Forest, Finance, West Bengal. He is an officer of 1996 batch of Indian Forest Service (West Bengal Cadre). He has two decades of experience working in Forest and Wildlife Maanagement and had worked in Sunderban Tiger Reserve for 10 years.  Dr. Shailendra Singh spearheads the India Program of Turtle Survival Alliance. He is Regional Vice Chair of  IUCN’s Tortoise and Freshwater Turtle Specialist Group - South Asia. With more than 18 years of experience, he supervises six long-term chelonians conservation projects in five Turtle Priority Areas (TPAs) in the country.  Mr. Dibyadeep Chatterjee, presently working as project associate at Wildlife Institute of India (WII) in the project entitled “Population management of species involved in human-wildlife conflict”. He is also a PhD affiliate with the faculty of wildlife sciences at WII.  Mr. Souritra Sharma, currently employed as project fellow under Wildlife Institute of India, Dehradun, Uttarakhand, for the project “Population management of species involved in human-wildlife conflict”.


Author contributions: Design and conception of the study: Nilanjan Mallick and Shailendra Singh.  Field setup design and structure: Nilanjan Mallick and Shailendra Singh.  Data collection and analysis: Shailendra Singh, Dibyadeep Chatterjee, and Souritra Sharma.  Wrote the paper: Shailendra Singh, Dibyadeep Chatterjee, and Souritra Sharma.


Ethical Standards: All the required work has been done in accordance with the ethical standards and under the permit from the principal chief conservator of forests, wildlife 448/41/4R-1(pt-VIII) 10 dated 15 th February, 2010.


Acknowledgements: We are thankful to Sri Ravi Kant Sinha, principal chief conservator of forests and head of forest force, West Bengal for constant encouragement and permit 448/41/4R-1(pt-VIII) 10 dated 15 February, 2010.  We sincerely thank Sri. V.K Yadav PCCF(WL - West Bengal) and chief wildlife warden for his guidance and support. We would also like to thank Sri Piar Chand, additional principal chief conservator of forest (APCCF) and director, Sundarban Biosphere Reserve for providing support and facilities towards setting up of breeding facility.  We would like to thank Mr. Soumitra Dasgupta, former field director, STR.  We also thank the veterinary officer of Sundarban Tiger Reserve, Dr. Sankar Sekhar Biswas, for helping in monitoring the health of turtles during the initial stages of the project.  SS thanks various organisations such as IUCN Save our Species (SOS); Ocean Park Conservation Fund, Hong Kong; People Trust for Endangered Species, Auckland Zoo and Alan and Patricia Koval Foundation for funding various scientific component of the project between 2012–2019.  Madras Crocodile Bank Trust/Centre for Herpetology is thanked for providing technical inputs.  Mr Rick Hudson, Mr Andrew Walde, Dr Gerald Kuchling, Mr Lonnie McCaskill are thanked for suggestions and inputs.  Dr Niladri Dasgupta, Dr Disha Sharma, Dr. Preeti Goswami, Mr. Shashwat Sirsi, Mr Saurav Gawan, Mr Sayantan Ghosh are thanked for assistance in field and data collection.  West Bengal State Zoo Authority provided additional funding for building assurance colonies.  Various officers and staff members of Sunderban Tiger Reserve are thanked for logistics helps.



Abstract: The population of Northern River Terrapin Batagur baska is ‘Critically Endangered’ and threatened with extinction.  In India, the species was once known to occur in the mangroves of West Bengal and Odisha.  The sub-population in Odisha is suspected to have been wiped out.  The Sundarban Tiger Reserve and the Turtle Survival Alliance launched a modest conservation breeding program in 2012 to recover the species using a small number of adults as founders.  Gravid adult females are kept in a dedicated breeding enclosure with minimal disturbance, eggs are incubated outdoor on an artificial nesting beach, and hatchlings are raised to develop assurance colonies for purposes of reintroduction in future.  Currently, the project holds 12 adults and over 350 juveniles of various size classes.  Three additional assurance colonies were developed for 70 sub-adults from 2012–13 batches, using rain-fed ponds within STR.


Keywords: Critically Endangered, Four-toed Terrapin, Freshwater turtles, Geomydidae, river turtle, Testudines.







Distribution and status of Batagur baska

The Indian subcontinent has one of the richest assemblages of chelonians in the world, with 29 freshwater turtles (Mital et. al 2019) and tortoises, of which all the members of the genus Batagur are seriously threatened.  Batagur baska (Gray, 1830), commonly known as the Northern River Terrapin or Four-toed Terrapin, is a giant river turtle belonging to the family Geoemydidae within the order Testudines.  B. baska is listed as ‘Critically Endangered’ in the IUCN Red List (Praschag & Singh 2019), and is recognised as one of the top 25 endangered turtle species in world (Turtle Conservation Coalitions 2018).  The species is also listed in the Appendix–I of the CITES.

Formerly believed to have been a single species ranging across the entire southeastern Asian region, B. baska is actually one of two genetically distinct species (Praschag et al., 2007).  The populations of river terrapins of Thailand, Malaysia, and Indonesia are now listed as the Southern River Terrapin Batagur affinis, while the northern species from India to Myanmar has retained the name B. baska (Praschag et al. 2008b, 2009; Weissenbacher et al. 2015; Praschag & Singh 2019).

Historically, B. baska was found in Odisha and the Hooghly River mouth, West Bengal (Blyth in. Gunther, 1864) in India, through to Bangladesh and Myanmar (lower Ayayarwady, Sittanug, and Thanlwin), and possibly as far south as the Andaman Sea side of Thailand at the Kra River.  Batagur was distributed in all the coastal districts of Odisha (Orissa), particularly the deltaic regions of Mahanadi, Brahmani, Baitarani, Dhamra and Subarnarekha, but Mishra, et al. (1996) believed it might have got extinct.  During the last recorded river survey in West Bengal and Odisha, while no evidence of a single population of B. baska was found from well-known habitats of this species in Odisha (Praschag et. al 2008a), nesting females were confirmed to be surviving in the Indian Sundarbans of West Bengal.  Furthermore, of the last 10 nesting females informed by Bhupathy (1995), Prachag’s survey only reported one of these females to be nesting on the beaches of Mechhua Island (Praschag 2008a; Moll et al. 2009).  B. baska is now primarily limited to the Sundarbans area of India and Bangladesh, with the exception of three females in two different temple ponds in Myanmar (Praschag & Singh 2019).

Though an aquatic species, it also uses sandy nesting beaches along the sea, frequenting the tidal zones of estuaries, large rivers and mangroves (Asian Turtle Trade Working Group, 2000).  Nests are often subject to predation by Water Monitor Lizards Varanus salvator or Rhesus Macaques Macaca mulatta.  Singh et al. (2014) also found spoors and signs of severe digging by Wild Boar Sus scrofa, possibly in search of turtle nests in Mechhua and other sea facing sandy beaches in the Indian Sundarbans.  Also, intense exploitation of the eggs and adults pertaining to illegal wildlife trade is considered to be the key driver of massive decline of Batagur population.

With an estimate of less than 40 animals in India (Praschag & Singh 2019) the only plausible solution to recover this species is conservation breeding followed by supplementation in the wild.  Sundarban is the only known abode of B. baska in India, and some successful hatching of the species has occurred at the Madras Crocodile Bank Trust (Whitaker, in Singh 2014).  West Bengal Forest Department, with the help of the Turtle Survival Alliance (TSA) has been attempting to recover Batagur baska species since 2008.  In August of the same year, 12 adults were captured and examined by researchers with assistance from local fishermen in the Sajnekhali range of the Indian Sundarbans (Singh & Saha 2008), which led to re-instating the breeding programme in the STR after a gap of about 20 years.  The objective in the present note is to put in record the information about the efforts made for conservation of B. baska in Sundarbans, West Bengal in India. 




The Batagur population

The local Bengali name for Batagur baska is ‘pore katha’ for male, and ‘sundi’ or ‘balli katha’ for female (Das 1985).  Since the 1980’s ex situ conservation program for the Olive Ridley Turtle Lepidochely solivacea was operational in STR, when eggs of the species were collected from wild nests and incubated in controlled environment at Sajnekhali.  Subsequently, the hatchlings were released in the sea.  During the nesting season of 1983, amongst the Olive Ridley hatchlings there were nine hatchlings of some other species, which were later identified as B. baska (Ghosh & Mandal 1990).

In 1988, three clutches of eggs of Batagur were translocated from Mechhua to Parkhiralaya (Ghosh & Mandal 1990), followed by 24 more nests in 1988 to 1991 (Ghosh & Mandal 1990; Moll et al. 2009).  Subsequently, the West Bengal Forest Department began captive breeding followed by hatch-and-release program for B. baska in the Sajnekhali Range Station within STR, where less than 50% of the eggs hatched after artificial incubation (Bhupathy et al 1995).  In the late 1990s, the hatch-and-release program was abandoned and the remaining captives were subsequently released in nature (Moll et al. 2009).

Observations recorded from Sajnekhali or its surroundings from 2008 onwards included detection of turtles, their relocations, occasional escapes, nesting, collection of eggs, incubation of eggs under supervision, hatching of young turtles, and housing of turtles in the available facility (Singh & Saha 2008; Pandit 2013; Singh 2013).  


Housing facilities for Batagur in Sajnekhali, Sundarbans

1. The breeding enclosure, built in 2018 is of length (L) x width (W) x depth (D) of 16.40m × 14.50m x 9m, provided with artificial sand bank (7m × 5.8m) for nesting and two basking platform of 3m ×3m size (Figure 3 iii).  The enclosure is covered with agro-net, topped with nylon net fencing to avoid predators as well as excessive sun.  Females Batagurs of 2012 constituted the founder colony for nesting (Table 1).

2. The temporary nesting enclosure/ yearling pool is a make-shift ‘8’-shaped enclosure, measuring LxWxD 20.6m × 5.5-9.40m x 3.5m (Figure 3 i), with nylon net fencing on all sides.  During the nesting season a few gravid females are shifted here for nesting.  The turtles of 2016 batch are also retained here.

3. The retention pond is an earthen pond of 39.70m x 35.31m size x 3.65m depth (Figure 3 ii).  It is the main holding facility in Sundarbans.  It holds Batagurs of the founder colony and turtles of batch 2013 and 2014.

4. The old nursery is 7.55m x 3.5m x 50cm (Figure 3; no. v) and the new nursery is 9m x 2.5m x 70cm (Figure 3 iv) with two hatchling ponds.  This facility is enclosed from all sides for thermoregulation and to avoid predation.  After the incubation period of about 60 to 66 days the hatchlings are collected and shifted to this enclosure.  After the transfer, hatchlings are retained here for the next six months.


Assurance facilities at Chamta, Jhingekhali, and Netidhopani and their usage

As the Sundarbans is prone to storm, it became essential to set up assurance colonies in order to avoid total wipe-outs, as was feared in 2009, when tropical storm Aila hit the Sundarbans, when one adult male escaped due to overflow of water from the original earthen pond.  Aiming for circumventing overcrowding, natural disaster and also as a precautionary measure in case of an outbreak of any contagious disease, the assurance colony ponds were set up at three islands namely Chamta, Jhingekhali, and Netidhopani, near forest department head-quarters, besides Sajnekhali, within STR.

These facilities are rain-fed earthen ponds, the embankments of which are fenced to ward off predatory animals such as V. salvator.  These ponds measure, Netidhopani: 40m x 7m x 2m depth (Figure 4, i); Chamta: 30m x 32m x 3m depth (Figure 4, ii), and Jhingekhali: 25m x 16m x 2m (Figure 4, iii).

Turtles from the 2012–2014 batches were transferred to these ponds, and now they hold 70 individuals of B.baska juveniles and subadults.  Other shifting were 20 individuals (13 female, 7 male) in March 2017, 34 in September 2017 to the Netidhopani sweet water pond and 16 individuals (13 female, 3 male) in November 2017 to the Jhingekhali sweet water pond.


The characteristics of water in captivity

The pH of Sajnekhali rain-fed pond is 7.68 and the salinity is 0.86 PSU, assumed to be conducive for long term retention of the species.  Thus, basic physiochemical parameters of the three assurance colony ponds were tested (Table 2) to keep the level of salinity and pH adjusted in reference to the Sajnekhali; however, the result depicted a higher measure of salinity in the pond located at Jhingekhali compared to other ponds (Figure 2).  Therefore, all three ponds were conditioned by adding fresh river water to keep the salinity under 10 part per thousand (ppt), and to correct the alkalinity and pH of the water matching with the specifications of the Sajnekhali Pond.


Hatching of the eggs and tending of the hatchlings and transfer to yearling pool

Gravid females after examination for calcified eggs in late February or early March are shifted to the breeding pond for nesting.  By the third week of March the females lay their eggs, which are determined with emergence, nesting tracks and camouflaging of nest cavity by the females.  During 2015 and 2018, no eggs hatched, the reason for which is non-conclusive

The eggs laid by the females are kept on an artificial sand beach and a temperature of about 30–32 °C is maintained by mimicking the reported nest depth and providing additional shade in breeding enclosure.  Temperature and humidity of the nest were continuously tracked using temperature data loggers.  After an incubation period of about 60–66 days the eggs hatch during end of May.  The hatchlings are then collected and shifted to the nursery (hatchling enclosure).  The artificial nesting bed is monitored for about five days from the time of emergence of the first hatchling.  Generally, all the eggs hatch in about two days’ time.  The hatchlings are transferred to the nursery pens, and are fed with aquatic plants and vegetables for the next six months.  After one year, when the hatchlings weigh approximately 250g, they are transferred to the yearling ponds, which offer a larger area and deeper water.

In July 2018, five juveniles from the 2017 batch showed symptoms like sloughing off part of the face, including the mouth region, nose and eye.  Two of these individuals succumbed to death during treatment.  Four swab samples examined at the Institute of Animal Health and Veterinary Biologicals, Kolkata tested negative for bacteriological infections, but tested positive for the Herpesvirus glycoprotein B.  All the infected individuals died in a few weeks’ time and carcasses were carefully disposed.  The remaining non-infected individuals were taken out of the adult pool for necessary treatment and observation and later quarantined as a precaution.

Currently, there is no data on survival and dispersal of Batagur in Sundarban.  The soft-release enclosure was blown away in a storm in February 2016 and all 10 telemetered animals escaped.





Batagur baska is not known to have any viable wild population in the last 20 years, which possibly suggest that the species has become functionally extinct from much of its range.  Sundarbans Tiger Reserve has carried out assisted breeding program since 2012, and has 359 individuals in captivity today, making it the largest holding of Batagur anywhere.  Batagur recovery initiative is also carried out in Bangladesh in association with Vienna Zoo and TSA.  The present account shows that the entire process in Sundarbans has been a learning experience.



Table 1. Year-wise captive stock of Batagur baska in Sundarbans




Place of housing



12 founders

Reported from Sajnekhali pond

Retention pond at Sajnekhali

Founder colony


33 hatchlings

founder colony of 12 individuals

Retention pond at Sajnekhali

Development of assurance colony and wild supplementation


55 hatchlings

Founder colony of 12 individuals

Retention pond at Sanjekhali

Development of assurance colony and wild supplementation


57 hatchlings

Founder colony of 12 individuals

Retention pond at Sanjekhali

Development of a ssurance colony and wild supplementation


96 hatchlings

Founder colony of 12 individuals

Temporary breeding cum holding facility in Sajnekhali

Development of assurance colony, survival dispersal study


74 hatchlings in 2017,

Founder colony of 12 individuals

Old Nursery in Sajnekhali

Development of assurance colony and wild supplementation


50 hatchlings

Founder colony of 12 individuals

New Nursery in Sajnekhali

Development of assurance colony and wild supplementation



Table 2. Results of water tests done on three assurance colonies by an external laboratory recognised by the West Bengal Pollution Control Board.


Assurance colonies





pH Value (at 25"C)

(APHA 22ND'Edition4. 500-H -B)




Total Alkalinity (as CaCO3), mg/ml 

(IS: 3025(Part-23)-I986)




Nitrate (as NO3), mg/ml 

(APHA 22ND Edition,4 500N Or'E)

< 0.5

< 0.5

< 0.5

Salinity (PSU)

(Electrical Conductivity Method)


< 0.5



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