American Trail keepers at the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) are in mourning following the sudden passing of Nick, an 18-year-old California sea lion, on August 7, 2025. The average life expectancy for California sea lions in human care is 23 years, making Nick’s death particularly poignant for both the caretakers and visitors who loved him.
Nick first showed changes in behavior on July 14, exhibiting a lack of appetite and decreased energy. Despite receiving pain relief medication and thorough examinations by the zoo’s veterinary team, his condition continued to decline. Tragically, while undergoing a full examination that included anesthesia to better assess his health, Nick went into cardiac arrest and could not be revived despite the staff’s best efforts. A final pathology report is anticipated to shed more light on the circumstances of his death in the coming weeks.
Victoria Adams, an American Trail keeper, expressed the joy Nick brought to the zoo, stating, “Nick was such a delightful sea lion to see and experience here at American Trail. Visitors from all over were astonished to see how strong and smart he was and see his unique variety of special training behaviors.” Katelyn Stache, assistant curator of carnivores at the Denver Zoo Conservation Alliance (DZCA), highlighted Nick’s loving nature and the joy he brought to community educational efforts, recalling his fame for his playful demeanor and impressive range of vocalizations.
Nick was rescued from Laguna Beach, California, as a newborn, left alone with his umbilical cord still attached. After being hand-reared at the Pacific Marine Mammal Center, he was deemed unreleasable and later transferred to the DZCA in Denver. Nick arrived at NZCBI on October 6, 2023, and was set to return to DZCA following renovations. His charming personality and unique abilities made him a significant ambassador for marine conservation, as he inspired countless visitors about the importance of protecting ocean wildlife.
Despite being classified as “of least concern” by the International Union for Conservation of Nature, California sea lions still face challenges such as human conflict and ocean pollution. Individuals can contribute to the protection of marine mammals by reducing single-use plastics and recycling, as well as opting for sustainably sourced seafood.
Nick’s legacy will continue through his two pups, Gunnison and Ady, and his mate, Luci, ensuring that the impact he had on the lives of his caretakers and the larger community will not be forgotten. His story emphasizes the importance of marine conservation and the collective effort needed to safeguard our ocean environments.