Data from: Infanticide as a male reproductive strategy has a nutritive risk effect in brown bears

Behavioral strategies to reduce predation can incur costs (i.e. risk effects). A common strategy to avoid predation is spatiotemporal avoidance of predators, in which prey typically trade optimal resources for safety. Analogous with predator-prey theory, risk effects should also arise in species with sexually selected infanticide (SSI), in which females with dependent offspring avoid infanticidal males. In brown bears (Ursus arctos), SSI is common and explains spatiotemporal segregation among reproductive classes. Here, we show that females with cubs-of-the-year had lower quality diets than conspecifics during the SSI high-risk period, the mating season. After the mating season, their diets were of similar quality to diets of their conspecifics. Our results suggest a nutritive risk effect of SSI, in which females with cubs-of-the-year alter their resource selection and trade optimal resources for offspring safety. We suggest that risk effects can be widespread among species with SSI, and that these risk effects can add to the female costs of reproduction.

降低捕食风险的行为策略往往会带来代价，即风险效应（risk effects）。规避捕食的常见策略为时空上避开捕食者，在此情境中猎物通常会牺牲最优资源以换取生存安全。与捕食者-猎物理论类似，存在性选择杀婴（sexually selected infanticide，SSI）的物种中也应存在风险效应，这类物种里携带依赖子代的雌性会避开具有杀婴行为的雄性。在棕熊（Ursus arctos）种群中，性选择杀婴现象较为普遍，且该现象可解释繁殖类群间的时空分隔现象。本研究发现，在性选择杀婴的高风险时期——即交配季，携带当年幼崽的雌性的日粮质量低于同种个体。交配季结束后，这类雌性的日粮质量则与同种个体无显著差异。本研究结果表明，性选择杀婴存在营养层面的风险效应：携带当年幼崽的雌性会调整其资源选择策略，以牺牲最优资源为代价换取子代的安全。我们推测，风险效应在存在性选择杀婴的物种中可能广泛存在，且此类风险效应会进一步增加雌性个体的繁殖代价。