Unwilling to leave, unable to stay: mechanism of plasticity in site fidelity as a rewarding tactic in changing environments

Abstract Context Home-ranging is common among animal species, as site fidelity facilitates cognitive map development and promotes efficient habitat use. The adaptive value of site fidelity, however, should decline as habitat conditions change, yet empirical evidence remains limited, especially for wide-ranging species. Objectives We investigated how fire and forest harvesting affect home-range stability in boreal caribou, a species typically exhibiting strong site fidelity. We then identified conditions where fidelity increases mortality and when shifting home ranges becomes advantageous. Methods We monitored 331 GPS-collared caribou across 667,000 km 2 of boreal forest. Forest harvesting and fire disturbance levels were related to indices of home-range fidelity derived from the spatial proximity of locations across successive years. Survival was then evaluated in relation to habitat conditions following home-range adjustment. Results Recent forest disturbances reduced fidelity, indicating behavioral plasticity. However, the fitness consequences of fidelity were strongly context‑dependent. High fidelity reduced mortality level when individuals occupied or selected low‑disturbance home ranges, but increased mortality when individuals remained faithful to highly disturbed ranges, particularly those dominated by regenerating cuts. Conclusions The study provides empirical evidence that site fidelity acts as both an adaptive strategy and a liability, depending on disturbance context and scale. By linking disturbance history, behavioral decisions, and survival outcomes, our analyses demonstrate how home-range fidelity mediates indirect pathways to mortality and may create fidelity‑induced ecological traps. These findings highlight the importance of maintaining large, connected areas of low disturbance to preserve the adaptive value of site fidelity in threatened caribou populations.