Behavioural adaptation to local conditions shapes brown bear coexistence with humans in heterogeneous landscapes

Understanding large carnivore behaviour in human-modified landscapes is essential for their conservation, yet behavioural responses reflect a complex interplay of anthropogenic, environmental, and demographic factors. To understand these responses, we leveraged a natural experiment in the Cantabrian range, which hosts one of Europe's most threatened native brown bear populations and comprises two subpopulations (eastern and western) differing in bear densities and landscape characteristics. Using GPS data from eleven western males, three western females and four eastern males, we compared seasonal movements, space use, and fine-scale habitat selection between subpopulations. Eastern males had the largest home ranges and longest daily movements during the mating period, consistent with the roam-to-mate hypothesis and the lower bear subpopulation density. They also strongly avoided roads and croplands, suggesting cautious behaviour toward humans. Conversely, western bears showed greater tolerance of human-modified areas and spent more time in their surroundings, possibly displaced by higher conspecific pressure under a despotic distribution. This greater tolerance could be transmitted between generations and be facilitated by the ruggedness and spatial configuration of the west, which may have allowed bears to access resources in rural valley bottoms and habituate to human proximity while minimising direct encounters through vertical partitioning. While western bears' tolerance makes conflict prevention an immediate priority, the ongoing eastern recovery warrants proactive coexistence measures, as increasing bear densities could progressively push individuals toward anthropogenic areas. The divergent strategies observed in adult males, even within the same population, highlight bear behavioural plasticity and the need for context-specific management to foster coexistence.