Abstract
<title>Abstract</title> <p> Headstarting, or rear-and-release, is a widely used conservation intervention that assumes animals raised in captivity to a larger size have better survival than if left in the wild. It has been the main conservation intervention for the critically endangered gharial ( <italic>Gavialis gangeticus</italic> ) since the 1970s, yet most populations have not recovered. In Chitwan National Park, Nepal, recruitment of headstarted individuals into the adult population remains poorly understood, so we used VHF radio telemetry to monitor survival, dispersal, and residency of released gharial (n = 20). Most individuals dispersed 20–60 km (mean=47km) downstream during an initial exploratory phase, after which some established residency. Individuals that established residency were significantly smaller, both overall and relative to age, than those that did not. Larger gharial showed no improved survival, and post-release mortality was high, with 25–50% dying within two years, mostly due to gill-net bycatch. Our findings show telemetry is a useful tool for post-release monitoring, helping explain survival outcomes and evaluate release strategies. In Chitwan, reducing bycatch remains critical for population recovery. Releasing gharial upstream of suitable habitat, before the monsoon, and at smaller sizes may improve outcomes. More broadly, our results suggest the core assumption of headstarting—that bigger is better, regardless of captive rearing—should be critically evaluated across species and systems. </p>