Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation

Abstract The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat...

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Autores principales:	Gaurav Vashistha, Ninad Avinash Mungi, Jeffrey W. Lang, Vivek Ranjan, Parag Madhukar Dhakate, Faiyaz Ahmad Khudsar, David Kothamasi
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/f5ac14c28dd14de2ba4c655d41927f84
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spelling	oai:doaj.org-article:f5ac14c28dd14de2ba4c655d41927f842021-12-02T13:33:44ZGharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation10.1038/s41598-021-84143-72045-2322https://doaj.org/article/f5ac14c28dd14de2ba4c655d41927f842021-02-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-84143-7https://doaj.org/toc/2045-2322Abstract The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverbank of the Girwa River. A natural channel shift in the mainstream Karnali River (upstream in Nepal) has reduced seasonal flow in the Girwa stretch where gharials nest, coincident with a gradual loss of nest sites, which in turn was related to an overall shift to woody vegetation at these sites. To understand how these changes in riparian vegetation on riverbanks were related to gharial nesting, we sampled vegetation at these sites from 2017 to 2019, and derived an Enhanced Vegetation Index (EVI) from LANDSAT 8 satellite data to quantify riverside vegetation from 1988 through 2019. We found that sampled sites transitioned to woody cover, the number of nesting sites declined, and the number of nests were reduced by > 40%. At these sites, after the channel shift, woody vegetation replaced open sites that predominated prior to the channel shift. Our findings indicate that the lack of open riverbanks and the increase in woody vegetation at potential nesting sites threatens the reproductive success of the KWS gharial population. This population persists today in a regulated river ecosystem, and nests in an altered riparian habitat which appears to be increasingly unsuitable for the continued successful recruitment of breeding adults. This second-ranking, critically endangered remnant population may have incurred an "extinction debt" by living in a reservoir that will lead to its eventual extirpation.Gaurav VashisthaNinad Avinash MungiJeffrey W. LangVivek RanjanParag Madhukar DhakateFaiyaz Ahmad KhudsarDavid KothamasiNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Gaurav Vashistha Ninad Avinash Mungi Jeffrey W. Lang Vivek Ranjan Parag Madhukar Dhakate Faiyaz Ahmad Khudsar David Kothamasi Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
description	Abstract The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverbank of the Girwa River. A natural channel shift in the mainstream Karnali River (upstream in Nepal) has reduced seasonal flow in the Girwa stretch where gharials nest, coincident with a gradual loss of nest sites, which in turn was related to an overall shift to woody vegetation at these sites. To understand how these changes in riparian vegetation on riverbanks were related to gharial nesting, we sampled vegetation at these sites from 2017 to 2019, and derived an Enhanced Vegetation Index (EVI) from LANDSAT 8 satellite data to quantify riverside vegetation from 1988 through 2019. We found that sampled sites transitioned to woody cover, the number of nesting sites declined, and the number of nests were reduced by > 40%. At these sites, after the channel shift, woody vegetation replaced open sites that predominated prior to the channel shift. Our findings indicate that the lack of open riverbanks and the increase in woody vegetation at potential nesting sites threatens the reproductive success of the KWS gharial population. This population persists today in a regulated river ecosystem, and nests in an altered riparian habitat which appears to be increasingly unsuitable for the continued successful recruitment of breeding adults. This second-ranking, critically endangered remnant population may have incurred an "extinction debt" by living in a reservoir that will lead to its eventual extirpation.
format	article
author	Gaurav Vashistha Ninad Avinash Mungi Jeffrey W. Lang Vivek Ranjan Parag Madhukar Dhakate Faiyaz Ahmad Khudsar David Kothamasi
author_facet	Gaurav Vashistha Ninad Avinash Mungi Jeffrey W. Lang Vivek Ranjan Parag Madhukar Dhakate Faiyaz Ahmad Khudsar David Kothamasi
author_sort	Gaurav Vashistha
title	Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
title_short	Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
title_full	Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
title_fullStr	Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
title_full_unstemmed	Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
title_sort	gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/f5ac14c28dd14de2ba4c655d41927f84
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Gharial nesting in a reservoir is limited by reduced river flow and by increased bank vegetation

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