Predator Avoidance Influences Selection of Neonatal Lambing Habitat by Sierra Nevada Bighorn Sheep

To improve lifetime reproductive success, maternal ungulates should pursue behavioral strategies that reduce risk of offspring mortality. Predation is a leading cause of neonatal mortality; thus, maternal ungulates should select habitat that reduces risk of predation on vulnerable neonates. We examined selection of habitat across subpopulations of federally endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae) within Sierra Nevada, California, USA, 2008-2018. Our objectives were to understand how maternal Sierra Nevada bighorn minimize risk of predation through selection of habitat and to quantify current and future potential neonatal habitat across the Sierra Nevada. Mountain lions (Puma concolor) are the predominant predators of adult Sierra Nevada bighorn; thus, we hypothesized females would select habitat that minimized risk of predation from mountain lions. We developed a used-available resource selection function to quantify patterns of habitat selection and produced predictive maps identifying highly selected lambing habitat across the Sierra Nevada. Our top model demonstrated females selected habitat where the relative probability of encountering mountain lions was low and near escape terrain. Selection for vegetation type was dependent on risk of encounter with mountain lions; when risk of encounter was low, females selected shrub cover. This suggests that when risk of encountering mountain lions was low, females may have selected areas with dense shrubs to reduce risk of being detected by other predators such as coyotes (Canis latrans) and golden eagles (Aquila chrysaetos). As risk of encountering mountain lions increased, females avoided all vegetation types other than barren, suggesting that despite increased risk of encounter, females may have been able to mitigate overall mortality risk by selecting habitat where approaching mountain lions could be detected and avoided. Our predictive models and resulting maps demonstrate differences in prevalence and connectivity of highly selected lambing habitat across subpopulations, which may explain differences in lamb recruitment and adequacy of lambing habitat observed among subpopulations. Recolonization into historical ranges and increasing connectivity between Sierra Nevada bighorn subpopulations is an important conservation need for species recovery and long-term viability of fragmented subpopulations.