A multi-method approach for the inventory of the adult population of a critically endangered crocodilian, the Gharial (Gavialis gangeticus) at Dhikala, Corbett Tiger Reserve incorporating direct counts and trail cameras

Chowfin, S. M.; Leslie, Alison J.

doi:10.5897/ijbc2013.0564

Cited by 9 publications

(2 citation statements)

References 7 publications

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“…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. Although all of these studies were daytime surveys similar to ours, direct comparisons of encounter rates are not justified because these populations probably differed with respect to population dynamics or management regimes, and were conducted in different years.…”

Section: Discussionmentioning

confidence: 98%

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

Bashyal

Shrestha

Luitel

et al. 2021

Aquatic Conservation

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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.

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Section: Discussionmentioning

confidence: 98%

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

Bashyal

Shrestha

Luitel

et al. 2021

Aquatic Conservation

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“…(2018) reported a relatively higher number of Gharials ( n = 33) in BNP compared to our study, possibly due to the use of a different survey method, namely the Unmanned Aerial Vehicle (UAV). While majority of Gharial studies (including this) (Bashyal et al., 2021; Chowfin & Leslie, 2014; Neupane et al., 2020; Nishan et al., 2023; Rajbhandari & Acharya, 2015; Singh & Rao, 2017) in multiple sites in India and Nepal employed visual encounter surveys (Crump et al., 1994) while sailing random transects along riverine habitat to estimate the Gharial population size.…”

Section: Discussionmentioning

confidence: 99%

Gharial (Gavialis gangeticus) conservation in Bardia National Park, Nepal: Assessing population structure and habitat characteristics along the river channel amidst infrastructure development

Dhami,

Maraseni,

Thapa

et al. 2023

Ecology and Evolution

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Nepal initiated numerous hydropower and irrigation‐related infrastructure projects to enhance and promote green energy, water security, and agricultural productivity. However, these projects may pose risks to natural habitats and the well‐being of aquatic fauna, leading to significant effects on delicate ecosystems. To understand these potential impacts, it is crucial to gather reliable baseline data on the population status and habitat characteristics of species. This study specifically focuses on Gharials (Gavialis gangeticus), a critically endangered species. We recorded data on pre‐determined habitat variables at stations spaced 500 m apart along the two major river streams of Bardia National Park, as well as at locations where Gharials were sighted between February and March 2023. We used binary logistic regression with a logit link function to investigate the habitat characteristics related to the occurrence of Gharials. The presence/absence of Gharials at sampling points served as the dependent variable, while 10 other predetermined variables (ecological variables and disturbance variables) served as independent variables. Our study recorded 23 Gharials, comprising 14 adults, six sub‐adults, and three juveniles, with a sex ratio of 55.56 males per 100 females. Most individuals (83%) were found basking. Among the 10 habitat predictors, three variables (mid‐river depth, river width, and water temperature) were significantly correlated (p < .05) with the probability of Gharial occurrence. The model shows that Gharial detection probability increases with greater mid‐river depth and width and lower water temperature. This study establishes a population baseline for Gharials within the river system before the construction of large infrastructure projects, such as dams and irrigation canals. It also recommends continuous monitoring of Gharial populations after water release and/or diversion to evaluate the impact of large infrastructure projects on the population and their associated habitat characteristics. This will help enable more informed and targeted conservation efforts.

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Differential response to disturbance factors for the population of sympatric crocodilians (Gavialis gangeticus and Crocodylus palustris) in Katarniaghat Wildlife Sanctuary, India

Choudhary

Choudhury

Gopi

2017

Aquatic Conservation

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1. Katarniaghat Wildlife Sanctuary along the Indo-Nepal border in India harbours a well-known breeding gharial (Gavialis gangeticus) population in its global distribution range together with a substantial population of breeding muggers (Crocodylus palustris). However, no systematic information on size and structure is available for either of the species' populations in the protected area.2. This study was undertaken in winter and the ensuing summer of 2010-2011 to estimate the relative population density and structure of the two crocodilian species and to examine the effect of various disturbance factors, with the main focus on the effects of tourism and illegal fishing on the behavioural attributes of the two species.3. Five daytime surveys were conducted from December 2010 to April 2011. Relative density based on encounter rate (number per 20 km) was highest for gharial juveniles followed by gharial adults and gharial sub-adults in all the five surveys. Muggers, on the other hand, showed the opposite trend, with the lowest encounter rate being for juveniles, followed by sub-adults and adults. The encounter rate of both species declined with increase in the mean ambient temperature from December to April. 4. The river habitat was divided into 2 km segments and disturbance factors were recorded at intervals of 100 m on both river banks. Wariness was taken as an indicator of response to disturbance caused by human beings and was measured from mechanized boats used for tourism and non-mechanized boats used for illegal fishing. 5. Segments with sandbars, in spite of moderate to high disturbance rate, were preferred for basking by both species. In conclusion, with suitable habitat for basking, gharials and muggers were observed to tolerate moderate levels of disturbance. Wariness resulting from disturbances from the non-mechanized boats was higher than that from the mechanized boats. Gharials tend to avoid humans, possibly with age/size acquired experience and knowledge, whereas muggers become more tolerant to human presence with increased age/size. 6. Despite many disturbance factors, the crocodilian population in Katarniaghat Wildlife Sanctuary is doing relatively well compared with populations in other habitats in India. With the involvement of local stakeholders and strict implementation of forest laws, the habitat can be further improved and a healthy gharial population can be ensured.

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A multi-method approach for the inventory of the adult population of a critically endangered crocodilian, the Gharial (Gavialis gangeticus) at Dhikala, Corbett Tiger Reserve incorporating direct counts and trail cameras

Cited by 9 publications

References 7 publications

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

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

Gharial (Gavialis gangeticus) conservation in Bardia National Park, Nepal: Assessing population structure and habitat characteristics along the river channel amidst infrastructure development

Differential response to disturbance factors for the population of sympatric crocodilians (Gavialis gangeticus and Crocodylus palustris) in Katarniaghat Wildlife Sanctuary, India

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