Increasing human activity in coastal habitats elevates the potential for wildlife disturbance. For southern sea otters (Enhydra lutris nereis), whose high metabolic rates require near-constant foraging, repeated disturbances can result in significant energetic costs. From 2015–2020, we conducted scan surveys at three California sites—Monterey, Moss Landing, and Morro Bay—to quantify sea otter behavior and exposure to potential disturbance stimuli. Using a hierarchical, process-based model, we examined how activity patterns changed with proximity to disturbance while accounting for site, group size, pup ratio, and kelp canopy presence. We linked behavioral responses to published activity-specific metabolic rates to estimate additional energetic costs associated with disturbance. Behavioral effects were location-specific and varied non-linearly with distance from disturbance stimuli. The likelihood of disturbance was <10% when stimuli were beyond 29 m, although this threshold varied by covariate. Estimated energetic costs increased 5–7%, with the greatest increases in Monterey’s Cannery Row area. Our findings provide a quantitative framework for assessing energetic consequences of human disturbance in marine mammals and inform management strategies to reduce impacts and promote coexistence between humans and recovering sea otter populations.

Heather E. Barrett is a marine ecologist and science communicator whose passion for wildlife ecology began early through youth biology education at the Lawrence Hall of Science and the UC Berkeley Botanical Garden. She earned her B.S. in Ecology and Evolution from UC Santa Cruz, working with Jim Estes lab and the Sea Otter Research and Conservation Program (SORAC) in collaboration with USGS and the Monterey Bay Aquarium. After several years with the California Department of Fish and Wildlife, Heather completed her M.S. at Moss Landing Marine Laboratories, where she studied the energetic costs of human disturbance to sea otters. As a Biologist and the Science Communication Director for Sea Otter Savvy, she integrates research and outreach to inspire coexistence between people and marine wildlife.