Herpetological Conservation and Biology 16(2):452–460. Submitted: 23 June 2020; Accepted: 8 July 2021; Published 31 August 2021. FEEDING ECOLOGY AND GROWTH PERFORMANCE OF THE CRITICALLY ENDANGERED BATAGUR BASKA IN CAPTIVITY NASRIN AKTER BRISTY1, MOHAMMAD FIROJ JAMAN1, A.G.J. MORSHED2, MD. MAHABUB ALAM1,4, MD. MOKHLESUR RAHMAN1, EBTISAMUL ZANNAT MIM1, 3 AND S.M. NAZMUL ALAM 1Department of Zoology, University of Dhaka, University Street, Nilkhet Road, Dhaka 1000, Bangladesh 2Project-Batagur Vienna Zoo, Maxingstraβe 13b, 1130 Vienna, Austria 3Department of Social Science, Curtin University, Perth, Kent Street, Western Australia 6102, Australia 4Corresponding author, e-mail: [email protected] Abstract.—We studied the feeding ecology of hatchling and juvenile Northern River Terrapin (Batagur baska) from April 2017 to April 2018 in captivity in Bangladesh. We made direct observations daily after providing foods in the late morning around 0930. We weighed food before and after the feeding season to measure the amount of food intake. We also obtained growth measurements at the end of the month. The consumption of greens was highest by the hatchlings (82%) and juveniles (73%), followed by vegetables (11% and 12%, respectively), fruits (6% and 10%), fresh shrimp (1% and 2%), and dry shrimp (0.3% and 2%). Food consumption and growth increased during the rainy and summer seasons. Food consumption was lower in January relative to the remainder of the year. Growth of juveniles increased from April to November and that of hatchlings from July to November. There were no substantial differences in food consumption among seasons. The relationship between food consumption and growth in body mass, carapace length, and plastron length were positive and significant for both juveniles and hatchlings. We also found positive and significant relationships between mean body mass and growth in carapace length and plastron length for both juveniles and hatchlings. Food consumption had significant and large effects on hatchling and juvenile growth. We found hatchlings attained higher growth rates than juveniles. Our study summarizes the food preferences, consumption rates, and associated growth rates that can be applied to range-wide captive breeding and rearing activities as a protocol for Batagur baska. Key Words.—Bangladesh; ex situ conservation; food and feeding; hatchlings; juveniles; Northern River Terrapin INTRODUCTION sand mining (Moll 1997; Moll et al. 2009; Pandit 2013; Behera et al. 2019), exploitation of eggs and adults, and The Northern River Terrapin, Batagur baska (Gray loss, degradation, and fragmentation of habitat (Pandit 1830), is one of the largest estuarine and long-lived 2013; Weissenbacher et al. 2015; Stanford et al. 2018; emydids in the world (Pandit 2013). Batagur baska Praschag and Singh 2019; Behera et al. 2019). Other has a distribution that includes India, Bangladesh, and causes of decline include the illegal turtle trade (Rashid Myanmar (Praschag et al. 2008a,b; Moll et al. 2009; and Khan 2000; Praschag and Singh 2019), incidental Weissenbacher et al. 2015; Praschag and Singh 2019). capture in fishing nets and traps, accidental death by During the 19th and 20th centuries, large populations of collision with motorboats, loss of nesting beaches, this species were present in the Hugli River of India and destructive fishing practices, and unseasonal floods the Ayeyarwady and Bago rivers of Myanmar (Praschag (Pandit 2013). These causes pose serious threats to et al. 2008a,b; Moll et al. 2009). In Bangladesh, B. this species globally, including in Bangladesh (Moll et baska is known to occur in large rivers and estuaries in al. 2009; Pandit 2013; Praschag and Singh 2019). The the coastal districts of Noakhali, Barisal, and Khulna species is now ranked as Critically Endangered (CR) (Morshed and Sobhan 2014). The global wild population globally by the International Union for Conservation of of B. baska has decreased by more than 90% over the Nature (Moll et al. 2009; Stanford et al. 2018; Praschag last two centuries. From being abundant in the 19th and Singh 2019) and regarded as one of the most Century, this species now has fewer than 100 mature threatened chelonians in the world (Das 1997; Rhodin individuals remaining (Praschag and Singh 2019). et al. 2018; Stanford et al. 2018). Batagur baska is Populations of this species have also been decimated also listed in the Convention on International Trade in in the wild in Bangladesh (Moll 2009; Weissenbacher Endangered Species of Wild Fauna and Flora (CITES) et al. 2015). This decline is attributable to a variety of Appendix I, where commercial trade of the species is causes, including removal of the mangrove forests and strictly prohibited (Praschag and Singh 2019). Copyright © 2021. Nasrin Akter Bristy 452 All Rights Reserved. Herpetological Conservation and Biology Understanding the feeding ecology of a species is an study. We obtained hatchlings after hatching of eggs essential component of assessing its ability to survive in June 2017 and no foods were provided that month, and is vital for management and conservation plans, but we measured their growth at the end of the month. whether in undisturbed or highly disturbed habitats We tagged both hatchlings and juveniles with Passive (Rahman et al. 2015). Batagur baska consumes Integrated Transponders (PITs) to enable individual whatever is available in their habitat to maximize the identification. Two of the 61 hatchlings died, one in daily intake of required energy and nutrients to thrive February and another in March of 2018. As a result, we and survive (Duli 2009). They are browsers, often studied 60 individuals in February and 59 individuals feeding sporadically for several hours before satiation in both March and April of that year. We differentiated (Moll et al. 2009). Most feeding occurs at high tide hatchlings and juveniles by their age and morphology. when vegetation is exposed and fruits from low hanging We distinguished juveniles from adults by size, carapace limbs hang down in the water (Moll 1984). The species shape, and plastron color (Pritchard and Trebbau 1984; is omnivorous but predominantly herbivorous from the Ernst and Barbour 1989). We confirmed that our turtles hatchling stage (Moll 1978, 1980; Pandit 2013). Besides were hatchlings after comparing our initial measurement leaves and stems, fruit (overwhelmingly mangrove fruit) of carapace length (CL), plastron length (PL), and body and mollusks shells (pelecypods of unidentified species) mass (BM) to the measurements of an average CL of 60 were found in the fecal samples of B. baska (Moll 1980; mm, PL of 55 mm (Edward O. Moll, unpubl. report), Whittaker 1983; Moll et al. 2009). and average BM of 45 g (Sanyal and Seth 1992). We Concerning their threatened conservation status, also considered hatchlings to be 11 mo old and juveniles the Bangladesh Forest Department, the Turtle Survival to be 34–45 mo old. During this study, we used two Alliance, Zoo Vienna, Austria, and Prokiti o Jibon large and five small tanks for rearing juveniles and Foundation, Bangladesh, have undertaken species hatchlings, respectively. We labeled each tank with the recovery efforts under Project Batagur. Recovery number of individuals it contained: tank number 1 had largely includes species reintroduction enabled by four juveniles, tank number 2 had one juvenile, and tank captive breeding efforts at Bhawal National Park in numbers 3–7 had nine, 10, 13, 13, and 16 hatchlings, Bangladesh (Morshed and Sobhan 2014; Weissenbacher respectively. We changed water in all tanks once a week et al. 2015). The knowledge obtained from zoo-based to maintain good water quality. We divided the study research is especially important for species whose period into summer (March-June), rainy season (July- natural population become limited or decimated, such October), and winter (November-February). as B. baska, and can also contribute significantly to the survival of offspring hatched or born in the natural Feeding protocols and monitoring.—We categorized habitat (Weissenbacher et al. 2015). Therefore, the food as greens including Water Hyacinth (Eichhornia current study aimed to investigate the preferred crassipes), Water Spinach (Ipomoea aquatica), Cabbage food items, monthly and seasonal variation in food (Brassica oleracea), and Taro (Colocasia esculenta) consumption, and growth response of hatchlings and leaves; fruits including banana (Musa sp.) and Jackfruit juveniles with foods provided in captivity. The study (Artocarpus heterophyllus); vegetables including Sweet provides baseline information and knowledge that Gourd (Cucurbita maxima) and Wax Gourd (Benincasa can be applied to future captive breeding and rearing hispida), and animals including fresh shrimp (Penaeus activities for population recovery programs. The study sp.), dry shrimp (Macrobrachium sp.), and mollusks will also provide insights for future conservation efforts (Pomacea sp.). We provided I. aquatica and E. crassipes of the species in Bangladesh or elsewhere in the world. following Nyok and Heng (2005), Moll et al. (2009), and Pandit (2013). We also followed Weissenbacher MATERIALS AND METHODS et al. (2015) and Nyok and Heng (2005) to provide fruits and animal food. We provided B. oleracea, C. Study area and tank facilities.—We conducted the esculenta, and vegetables (C. maxima, B. hispida) study from April 2017 to April 2018 at Bhawal National based on their omnivorous feeding habit. We offered Park, (24°5′45″N, 90°24′14″E), Gazipur, Bangladesh. hatchlings and juveniles the same food items provided This study site inside the park has 15 cement rearing on the surface of the water in each tank. We adjusted tanks for juveniles and hatchlings. Seven tanks were the amount of food according to the size and abundance large (4.27 × 3.04 × 0.91 m) and eight tanks were of hatchlings and juveniles in each tank. Among the smaller (1.83 × 1.83 × 0.91 m). Each tank has watering limited food supply in the project site, we measured and dewatering facilities, and the water depth of both feeding preferences for both hatchlings and juveniles sized tanks was 0.76 m.