Behavioral Plasticity of Female Northern Elephant Seals Drives Fine-Scale Foraging Success

Few studies have been able to evaluate foraging success and behaviors of top marine predators at the fine-scale spatial and temporal resolutions of their prey patches. Using a large, multi-year dataset of female northern elephant seal movement and diving behavior, we examined how a number of variables influenced foraging behaviors, and how changes in behaviors related to daily foraging success as inferred from in-situ measures of buoyancy change. Diving behavior was affected by many extrinsic (temperature and light level) and intrinsic (mass, age, and individual quality) factors. Daily foraging success was affected by several diving behaviors, clustered into three categories: bottom activity, depth of foraging zone, and vertical transit rate. Our results suggest that behaviors that reduced the energy invested into foraging dives were more important to foraging success than behaviors associated with increased prey encounters. Behaviors were variable between and within individuals and seasons. The behavioral responses to the environment appeared to be constrained by the metabolic costs of pregnancy. By modeling the fine-scale changes in behaviors and foraging success in this top marine predator, changes in ocean productivity and climate may be detected at small temporal and spatial scales.