Program on the Environment

The western population of Steller sea lions remains endangered 50 years after its historic decline. Researchers at the National Oceanic and Atmospheric Administration (NOAA) are examining population health and behaviors to understand why recovery has stalled. Through my internship with NOAA’s Marine Mammal Laboratory, I analyzed behavioral data collected from remote cameras in the Aleutian Islands to assess whether adult females are shifting their maternal care strategies over time. The purpose of this research was to examine whether adult females exhibit behaviors that prolong juvenile offspring’s dependence under unfavorable climatic conditions. Using observational data from two breeding grounds, Agattu and Ulak, I compared maternal behaviors from 2017 to 2023, with particular focus on the 2018 North Pacific marine heatwave. Results indicate a slight increase in adult females feeding juveniles via lactation during and for two years after the 2018 heatwave. These preliminary findings suggest that female Steller sea lions may preferentially extend the normal weaning period, maintaining offspring dependence on milk rather than solid food during periods of environmental stress, potentially improving juvenile survival rates. However, this strategy carries significant costs: energetic demands are highest during late lactation, placing the adult female’s health at risk and limiting future reproductive success. These findings (1) demonstrate the behavioral flexibility of Steller sea lions in response to environmental stress, (2) illustrate how climate change may influence maternal care strategies and population health, and (3) highlight the need for continued research into sea lion behavior and long-term monitoring efforts.