Imperiled populations globally face many interacting threats to their existence, including land use change, disease, and climate perturbations. As individuals are born, disperse, and reproduce, they experience these threats differentially and at both local and regional scales. The potential for complex interactions is high; for example, if land use change alters dispersal patterns, which in turn alter spread of disease. Here, we use statistical models to improve our understanding of imminent threats and their impact on the dynamics and dispersal behaviors of a species that has historically been threatened by environmental events and conflict with fisheries. The California sea lion, Zalophus californianus, lives along the pacific coast of Mexico and California. The collapse in marine productivity during El Nino decreases natality rates and maternal investment, and increases the numbers of stranded individuals. Some animals display behavioral differences in habitat use and range during El Nino events that can impact density and dispersal, and the potential for disease spread.
We found that initial weight was different for the sexes and that first year survival for sea lion pups increased with birth weight. There was a reduction in birth weight and an increase in pup mortality during higher sea surface temperatures (SST), which are associated with El Nino events and reduced marine productivity. High SST also impacted adult mortality and an individual’s tendency to disperse from natal location. Adult mortality also differed with age and sex. This information will be used to inform mathematical models of sea lion dynamics to address questions in the threatened and closely-related Galapagos sea lion. This will improve our understanding of imminent threats and their persistent impact on the dynamics of an endangered species. Population managers will be able to use this information to inform conservation efforts and sampling design for pinniped species.