Monitoring the movement, habitat use and mortality of captive‐bred reintroduced gharials in the Mahanadi River, India

Abstract

Abstract Gharials (Gavialis gangeticus) are endemic to the Indian subcontinent and meet IUCN Red List criteria for critically endangered. The Mahanadi River, located in the southernmost part of the gharial range, currently has a few individuals survived although historically had many more. Between 2019 and 2021, the movement, habitat use and survival rate of 13 captive‐bred (juvenile = 6, subadult = 5, adult = 2) reintroduced gharials were monitored using very high frequency (VHF) radio transmitters tracked manually from the river banks. Kernel density estimates and generalized linear model (GLM) were used to investigate the home range and habitat use of individuals. Tagged gharials travelled throughout the river system, with the highest movement during summer and the least in winter. Females moved further and established larger linear home ranges than males. Kernel home ranges were established in and around the Satkosia Gorge wildlife sanctuary, which has favourable ecological conditions for gharials, namely, deep water, sandbars, abundant fish and low human disturbance. Gharial mortality was detected during the study, and post‐mortem examination indicated anthropogenic causes. The use of explosives for fishing, entanglement in fishing nets and a lack of ecological awareness within local communities were identified as key factors that need to be addressed if gharials are to survive the Mahanadi River.