Gharials (Gavialis gangeticus) in Bardiya National Park, Nepal: Population, habitat and threats

Abstract

Abstract The Critically Endangered gharial (Gavialis gangeticus) residing within Bardiya National Park (BNP) in Nepal constitutes the sixth major sub‐population of this unique lineage; however, this population is not well studied. A 46 km protected stretch of the Babai River and a 60 km stretch of the Karnali River in and around BNP were surveyed for gharials in early 2017 and in 2019. Gharial counts in 2017 – 17 from the Babai and one from the Karnali rivers – consisted of 10 adults, five sub‐adults and three juveniles. In 2019, 19 gharials were counted – 18 for the Babai and one for the Karnali – comprising 11 adults, six sub‐adults and two juveniles. In the Babai River within BNP, four breeding groups were identified. Gharials in BNP prefer sandy vs. rocky banks for basking and completely avoid sand‐grass and clay banks. Habitat preference did not vary with size class. Protected stretches of both rivers inside BNP (76 km) have resident gharial, intact habitats and few human threats. In contrast, the unprotected stretch of the Karnali (30 km) is threatened by boulder quarrying, sand mining and unlicensed fishing, and is avoided by gharials despite the availability of habitat. This study established baseline data, including indices of population size, distribution and habitat preferences, and documented resident gharials that are breeding in the Babai River in BNP. The conservation of this Babai population is crucial for the species’ survival in BNP. Based on this study, we recommend the following conservation actions on the Babai stretch: (a) determine hatching success; (b) assess juvenile recruitment; (c) consider supplementation by releasing captives; (d) study riverine features important as baselines; (e) accommodate upstream movements on the protected Babai stretch; and (f) protect the downstream Babai outside the boundary of the BNP.