Stability of space use in Svalbard coastal female polar bears: intra-individual variability and influence of kinship

Philopatry influences animal distribution and can lead to a kinship-based spatial structure, where proximity and relatedness are tightly linked. In the Barents Sea region, polar bears (Ursus maritimus) of the coastal ecotype remain year-round within the Svalbard archipelago. This coastal strategy is thought to be stable across years; however, little is known about the intra-individual variability in site fidelity or the influence of kinship on space use. Using high-resolution GPS telemetry, we looked at multi-year philopatry among 17 coastal female polar bears over eight years (2011-19) and investigated whether it is linked to the females' degree of kinship. Individuals showed a stable space use in both consecutive and non-consecutive years. Yearly individual home ranges (HRs) overlapped, on average, by 44% (range: 9-96%), and their centroids were, on average, 15 km (range: 2-63 km) apart. The space use of related females revealed a year-round strong female kin structure. Annual HRs of related females overlapped, on average, by 24% (range: 0-66%), and their centroids were, on average, 18 km (range: 2-52 km) apart. In contrast, non-related females had much larger distances between centroids (average: 160 km, range: 59-283 km). Additionally, females showed a great site fidelity in all seasons: individual seasonal HR centroids were, on average, less than 30 km (range: 1.8-172 km) apart. Bears in this region seem to exhibit a stronger site fidelity than those reported from other parts of the species range. These findings also highlight the importance of maternal learning in space use.

Automated summary

The study revealed a stable philopatry behavior among coastal female polar bears in the Barents Sea region, with a strong kin structure among related females and significant differences in spatial use patterns between related and unrelated individuals. Additionally, the bears exhibited a high level of site fidelity, especially among females, with small distances between centroids of individual seasonal home ranges.