Population status, distribution and threats of the critically endangered Gharial (Gavialis gangeticus) in Narayani River of Chitwan National Park, Nepal

Abstract

The Gharial (Gavialis gangeticus), also known as the gavial or fish-eating crocodile, is a member of the family Gavialidae, is the most threatened of the two species of crocodilians found in Nepal. However, sufficient information on its habitat characteristics influencing population status, distribution, and threats to its existence are lacking. We studied the gharial population in the Narayani River that was carried out in the winter season during December 2019 to April of 2020. During our surveys, a total of 117 gharials were recorded, including an adult male, 56 adult females, 19 sub-adults, 32 immature and nine were unidentified. The gharial census recorded 57 gharials in Sikrauli-Amaltari (Chitwan branch) river section followed by 14 in Sikrauli-Amaltari (Nawalparasi branch), 16 in Amaltari-Baguwan and 30 in the Baguwan-Tribeni River sections. Of 117 individuals, the number of gharials sighted under the direct observation category was 112. The majority of respondents (129 of 140) during our questionnaire, considered gharial as an important species and displayed a favorable attitude towards gharial conservation. This study concludes that the population of gharial in the Narayani River has increased, as the present population is larger than recorded during previous surveys. Finally, regular surveys and monitoring of gharial in the area are recommended to investigate the status of gharial, the prevalence of any threats and disturbance along the habitat of this important species.

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

“…The results of this study showed that gharials prefer sandy banks for basking more than other habitat or substrate types. In Nepal, previous studies have found a similar selectivity for basking on sandy banks on the Narayani River (Maskey, 1989;Maskey, Percival & Abercrombie, 1995;Thanet, 2014;Rajbhandari & Acharya, 2015) and on the Rapti River (Bhatta, 2009). On the Chambal River in India, gharials also show a preference for sandy banks (Hussain, 2009;Katdare et al, 2011;Nair et al, 2012) without regard to availability.…”

“…Maskey (1989) sex ratio of 1:5 and Rajbhandari & Acharya (2015) reported a sex ratio of 1:12 in the Narayani River. A sex ratio of 1:9.5 was reported by Bhatta (2009) in the Rapti River in the CNP. The present study recorded a male to female ratio closer to 1:1 to 1:1.5 in the BNP in 2017 and 2019, respectively.…”

“…Encounter rates in the Babai and Karnali were consistent between years, but lower than encounter rates for gharials in other rivers in Nepal and in India. For instance, encounter rates were 0.52 (Rajbhandari & Acharya, 2013) and 0.6 in the Narayani River (Rajbhandari & Acharya, 2015), and 0.5 (Bhatta, 2009) and 0.7 in the Rapti River (Rajbhandari & Acharya, 2013) in CNP. Encounter rates were 1.11 (Katdare et al, 2011) and 2.04 (Hussain, 2009) in the Chambal River and 4.01 in the Dhikala River (Chowfin & Leslie, 2014) in India.…”

Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal

“…The direct count method showed that between 2004 and 2013, the Rapti River had a population of no more than 35 gharials (Acharya et al, 2017; Bhatta, 2009; Maskey et al, 2006). In 2016, their population increased to 82, and in 2017, it increased to 118 (Acharya et al, 2017; Poudyal et al, 2018).…”

“…Numerous studies have been conducted in the Rapti River to estimate gharial population since 1980s (Acharya et al, 2017; Ballouard & Cadi, 2005; Bhatta, 2009; DNPWC, 2018; Maskey, 1989, 1998; Mishra, 2002; Poudyal et al, 2018; Rajbhandari & Acharya, 2015). To the best of our knowledge, almost all the studies on population estimation of gharials in Nepal including the Rapti River have employed the direct count method whereby the number of observed gharials in stretch of river under consideration is counted to estimate their total count (Acharya et al, 2017; Ballouard & Cadi, 2005; Bashyal et al, 2021; Bhatta, 2009; DNPWC, 2018; Maskey, 1989, 1998; Mishra, 2002; Poudyal et al, 2018; Rajbhandari & Acharya, 2015). The direct count method, however, does not account for imperfect detection (Barão‐Nóbrega et al, 2022 and references therein).…”