ABSTRACT:

Juvenile stages are critical yet understudied periods in the life cycle of endangered hawksbill turtles (Eretmochelys imbricata). This study used Fastloc-GPS tracking to examine the home range and movement patterns of 19 immature hawksbills (mean curved carapace length ± SD = 56.1 ± 10.2 cm) across five neritic habitats around Reunion Island (mean tracking duration ± SD = 230 ±133 days). Eight tags were physically recovered, providing access to memory records, including wet/dry and sea temperature data. We investigated their spatiotemporal movement patterns, site fidelity, and habitat use dynamics across daily, monthly and seasonal timescales. The results revealed strong site fidelity, with 95% utilization distributions (UDs) averaging 0.79 km² (95% UD) and remaining highly stable over time. Daily activity patterns are closely linked to the sun’s angle, with the greatest spatial extent when the sun is highest and resting behaviours at night. Surface time, derived from wet/dry data, peaked in the morning and increased by a factor of 1.5–1.6 at lower sea temperatures (range = 24 – 28°C). Nocturnal site selection strongly influenced the extent of the home range, with most turtles favouring the night shelter closest to their core foraging ground. While small-scale exploratory movements (<5 km) were common (11 individuals), two turtles undertook long-range migrations (>1000 km), suggesting that juveniles transition through multiple developmental sites before adulthood. These findings provide new insights into the spatial variability of immature hawksbills, alternating between highly conservative behaviour and exploration, emphasizing the need for regional conservation strategies and site-specific protection.