What is home? Post-release movements of captive-reared and translocated mature saltwater crocodiles in Bangladesh

Context The ability of animals to exhibit homing behaviour, returning to familiar locations by using spatial memory, is central to understanding movement ecology, conservation planning, and the success of reintroduction programs. Despite this, little is known about the homing behaviour of mature captive-reared crocodiles once released into the wild. Aims This study investigated post-release movements of captive-reared, wild-caught, and translocated saltwater crocodiles (Crocodylus porosus) in Bangladesh’s Sundarbans mangrove ecosystem, with the aim of assessing homing tendencies and how movement patterns differ among release types. Methods Five mature crocodiles were monitored, including three captive-reared individuals, one wild-caught and released, and one wild-caught translocated animal. Satellite telemetry and continuous-time state-space modeling were applied to estimate daily movements and home-range sizes across tracking periods of 53–127 days per individual. Key results Movement patterns varied substantially among individuals. The translocated crocodile exhibited the greatest daily movements (up to 34.3 km/day) and an expansive home range (2515 km2), consistent with previously documented strong homing and exploratory responses to translocation. In contrast, captive-reared and wild-caught released crocodiles moved shorter daily distances and maintained smaller, more defined home ranges (14.2–125 km2). Importantly, captive-reared crocodiles showed no indication of homing towards prior husbandry sites, despite long-term captivity. Conclusions Mature captive-reared crocodiles were able to establish ranges in the wild without showing fidelity to former captive or husbandry sites. In contrast, the pronounced exploratory behaviour of the translocated crocodile underscores the challenges associated with adult translocations. Implications These findings highlight the potential of releasing subadult and adult captive-reared crocodiles as a viable conservation strategy to bolster wild populations while avoiding the high predation risks of juvenile releases. At the same time, they emphasise the importance of carefully considering release sites and incorporating measures such as soft-release protocols to mitigate homing behaviour in translocated animals. The results provide an evidence base for refining crocodile reintroduction and restocking efforts across their range.