Main Article Content
Supplementation of wild populations of the Critically Endangered Gharial Gavailis gangeticus with individuals reared in captivity is a widely used conservation management tool in Nepal and India, although its efficacy is uncertain. Measuring post-release growth in Gharial can provide valuable information on acclimation of captive-reared Gharial to the wild and provide growth rates to inform population recovery models. We studied post-release growth of Gharial reared in the Gharial Conservation Breeding Centre, Nepal, following their release into the Chitwan National Park. We used recapture data from known individuals to determine growth and change of mass for 26 Gharial recaptured 0.5–10 years after release. We found that Gharial recaptured two or more years post-release had increased in mass and length despite being over six years old at release, however there was a triangular relationship between time since release and growth: some Gharial had grown very slowly, whilst others had grown much faster. All Gharial recaptured less than two years since release had lost mass and had negligible growth in total length. This data show that there is considerable variation in post-release growth rates, which will lead to some individuals being very old before they reach a potentially mature size class, with unknown implications for reproduction. This variation is important for predicting or modelling recovery in populations where the release of Gharial from captivity is a management tool. Our results also suggest the two years after release are an acclimation phase—when Gharial lose mass and do not grow—which should be considered by release strategies in order to give Gharial the best chance of survival after release.
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors own the copyright to the articles published in JoTT. This is indicated explicitly in each publication. The authors grant permission to the publisher Wildlife Information Liaison Development (WILD) Society to publish the article in the Journal of Threatened Taxa. The authors recognize WILD as the original publisher, and to sell hard copies of the Journal and article to any buyer. JoTT is registered under the Creative Commons Attribution 4.0 International License (CC BY), which allows authors to retain copyright ownership. Under this license the authors allow anyone to download, cite, use the data, modify, reprint, copy and distribute provided the authors and source of publication are credited through appropriate citations (e.g., Son et al. (2016). Bats (Mammalia: Chiroptera) of the southeastern Truong Son Mountains, Quang Ngai Province, Vietnam. Journal of Threatened Taxa 8(7): 8953–8969. https://doi.org/10.11609/jott.27126.96.36.19953-8969). Users of the data do not require specific permission from the authors or the publisher.
Acharya, K.P., B.K. Khadka, S.R. Jnawali, S. Malla, S. Bhattarai, E. Wikramanayake & M. Köhl (2017). Conservation and Population Recovery of Gharials (Gavialis gangeticus) in Nepal. Herpetologica 73(2): 129–135. https://doi.org/10.1655/herpetologica-d-16-00048.1
Ballouard, J.M., P. Priol, J. Oison, A. Ciliberti & A. Cadi (2010). Does reintroduction stabilize the population of the critically endangered gharial (Gavialis gangeticus, Gavialidae) in Chitwan National Park, Nepal? Aquatic Conservation: Marine and Freshwater Ecosystems 20(7): 756–761. https://doi.org/10.1002/aqc.1151
Blake, D.K. & J.P. Loveridge (1975). The role of commercial crocodile farming in crocodile conservation. Biological Conservation 8(4): 261–272. https://doi.org/10.1016/0006-3207(75)90004-X
Czarnołe ‘ski, M. & J. Kozłowski (1998). Do Bertalanffy’s growth curves result from optimal resource allocation? Ecology Letters 1(1): 5–7. https://doi.org/10.1046/j.1461-0248.1998.0007b.x
De Vos, A. (1982). A Manual on Crocodile Conservation and Management in India. Food and Agriculture Organisation of the United Nations. Dehra Dun India, 69pp.
Elsey, R.M., T. Joanen, L. McNease & N. Kinler (1992). Growth rates and body condition factors of Alligator mississippiensis in coastal Louisiana wetlands: a comparison of wild and farm-released juveniles. Comparative Biochemistry and Physiology Part A: Physiology 103(4): 667–672. https://doi.org/10.1016/0300-9629(92)90164-L
Elsey, R.M., T. Joanen, L. McNease & V. Lance (1990). Growth rate and plasma corticosterone levels in juvenile alligators maintained at different stocking densities. Journal of Experimental Zoology 255(1): 30-36. https://doi.org/10.1002/jez.1402550106
Grigg, G. & D. Kirshner (2015). Biology and Evolution of Crocodylians. pp. 34-35. In: Biology and Evolution of Crocodylians. Cornell University Press, New York, 648pp.
Huchzermeyer, F.W. (2003). Crocodiles: Biology, Husbandry and Diseases. CABI, Wallingford, 352pp.
Khadka, B.B. (2010). Gharial hatching status in 2010, Chitwan National Park, Nepal. Crocodile Specialist Group Newsletter 3(29): 16–17.
Khadka, B.B. (2012). Gharial Released into Chitwan National Park, Nepal, January-April 2012. Crocodile Specialist Group Newsletter 31(2): 14–16.
Khadka, B.B. (2022). Habitat Assessment of the Rapti and Narayani Rivers and their Tributaries in Chitwan National Park. WWF Nepal. Kathmandu, Nepal, 19pp.
Khadka, B.B. & A. Bashyal (2019). Growth rate of captive Gharials Gavialis gangeticus (Gmelin, 1789)(Reptilia: Crocodylia: Gavialidae) in Chitwan National Park, Nepal. Journal of Threatened Taxa 11(15): 14998–15003. https://doi.org/10.11609/jott.54188.8.131.5298-15003
Koenker, R. (2020). quantreg: Quantile Regression. R package version 5.61.
Lang, J.W. (1987). Crocodilian thermal selection pp. 307–317. In: Webb, G., C. Manoli & P. Whitehead (eds.). Wildlife management: crocodiles and alligators. Surrey Beatty and Sons Pty Ltd, Chipping Norton, New South Wales, Australia, 552pp.
Maskey, T.M. (1989). Movement and Survival of Captive-Reared Gharial Gavialis gangeticus in the Narayani River, Nepal. PhD Thesis. University of Florida, xiii+187pp.
Maskey, T.M. & H.F. Percival (1998). Status and Conservation of Gharial in Nepal. pp. 77–83. In: XIIth Working Meeting of the Crocodile Specialist Group Pattaya, Thailand, 309pp.
Morici, L.A., R.M. Elsey & V.A. Lance (1997). Effects of long-term corticosterone implants on growth and immune function in juvenile alligators, Alligator mississippiensis. Journal of Experimental Zoology 279(2): 156–162. https://doi.org/10.1002/(SICI)1097-010X(19971001)279:2<156::AID-JEZ6>3.0.CO;2-N
R Core Team (2013). R: A language and environment for statistical computing. R Foundation for Statistical Computing. Vienna, Austria.
Singh, L.A.K. (1978). Ecological Studies on Indian Gharial, Gavialis gangeticus (Gmelin)(Reptilia, Crocodilia). PhD Thesis. Utkal University, India, 324pp.
Singh, L.A.K. (2018). Gharial is a Fish-Eating Crocodile, it’s Ecology, Behaviour and Conservation 1st ed. Lambert Academic Publishing, Beau Bassin, Mauritius, 268pp.
Teixeira, C.P., C.S. De Azevedo, M. Mendl, C.F. Cipreste & R.J. Young (2007). Revisiting translocation and reintroduction programmes: the importance of considering stress. Animal Behaviour 73(1): 1–13. https://doi.org/10.1016/j.anbehav.2006.06.002
Turton, J.A., P.W. Ladds, S.C. Manolis & G.J.W. Webb (1997). Relationship of blood corticosterone, immunoglobulin and haematological values in young crocodiles (Crocodylus porosus) to water temperature, clutch of origin and body weight. Australian Veterinary Journal 75(2): 114–119. https://doi.org/10.1111/j.1751-0813.1997.tb14170.x
Wickham, H. (2016). ggplot2: Elegant Graphics for Data Analysis. Springer-Verlag, New York, 276pp.