For decades, the headstarting programme in Chitwan National Park has been a cornerstone of gharial conservation in Nepal. Since 1978, hundreds of gharials have been reared in captivity and released into the wild. However, by 2016, conservationists faced a troubling reality: despite the release of 910 gharials between 1981 and 2016, the adult population in Chitwan remained stubbornly small.

The problem? A lack of post-release monitoring meant the causes of this limited recovery were poorly understood.

A Collaborative Effort to Understand the "Why"
From 2017 to 2023, through a collaborative project with the Department of National Parks and Wildlife Conservation, Chitwan National Park, and the National Trust for Nature Conservation, we embarked on a groundbreaking project. Using radiotelemetry, we tracked a cohort of 20 head-started gharials to investigate their survival and dispersal. In parallel, we analyzed 40 years of release and survey data to contextualize our findings.

The Hard Truths of Post-Release Survival
The results, published in our latest study, highlight the perilous journey these animals face after release:

• High Mortality: 25–50% of the tracked gharials died within two years of release. The predominant cause was bycatch in gill nets.
• Failure to Settle: Movement analysis revealed that one-third of the tracked individuals did not settle in a defined river stretch, suggesting a failure of post-release adaptation.
• The Size Paradox: Counterintuitively, larger release size did not result in improved survival. In fact, larger gharials were less likely to settle.
• Long-Distance Dispersal: Most gharials dispersed 20–60 km from their release sites, with some travelling substantially farther.

Why This Matters
This study demonstrates that post-release monitoring using telemetry is invaluable. Without it, mortality and maladaptive behaviors are likely to be underestimated or entirely undetected. High-resolution movement data and longer tracking durations (2+ years) are necessary to capture delayed mortality and prolonged adjustment periods.

The Path Forward
Our findings enable evidence-based refinement of head-starting approaches. By understanding the specific threats (like gill net bycatch) and behaviors (like failure to settle), we can support adaptive management and ensure that conservation investment is guided by demonstrable outcomes.

Watch the video to learn more about this research and the people behind it: https://www.youtube.com/watch?v=19XQraXE0AU