Why Size Does Not Matter: Sex Driven Home Range Differences in Brown Bears

Sex, body size and environmental conditions are key determinants of home range size in large mammals, yet their relative importance within populations remains unclear for many wide-ranging carnivores such as brown bears. This study combined GPS-collar data and detailed morphometrics from 69 free-ranging brown bears (46 males, 23 females) in Türkiye to test how home range size relates to sex, body mass, and body dimensions. Individual home ranges were estimated using 95% minimum convex polygon (MCP95) and kernel utilisation distribution methods, and the MCP95 area was log-transformed and analysed with linear models that included sex, log body mass, representative linear size measures, sampling effort covariates, and principal component scores derived from a multivariate analysis of eight morphometric traits. Home range size varied markedly among individuals (5.1-203.9 km²), with males consistently having nearly twice the MCP95 area of females, with sex accounting for most of the variance in log home range size. In contrast, neither body mass nor linear body dimensions showed significant within-sex relationships with home range size, and sex × mass interactions were not supported. Principal component analysis revealed a dominant body size axis, but this multivariate size component, as well as a secondary shape axis, did not explain additional variation once sex was included. Models that accounted for the number of GPS fixes, tracking duration, and influential points confirmed the robustness of the sex effect and indicated only modest contributions of sampling effort. Overall, the results showed that sex, rather than fine-scale variation in body size or shape, is the primary intrinsic driver of home range size in this southern brown bear population, highlighting the need for sex-specific but not size-specific spatial planning and conservation strategies in the future.