Zoo Staff Mourn the Loss of Sea Lion Nick

American Trail keepers at the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) are mourning the loss of Nick, an 18-year-old male California sea lion who died suddenly Aug. 7, 2025. The median life expectancy of California sea lions in human care is 23 years.

On July 14, keepers first noticed Nick had a decreased appetite and less energy than usual. After a consultation with the Zoo’s veterinary team, Nick received a pain medication due to concerns that discomfort could be resulting in his behavior change. However, Nick’s appetite did not improve, and he exhibited worsening weight loss and uncharacteristic behaviors, including avoiding his keepers and the other sea lions. On Aug. 7, the Zoo’s veterinary team undertook a full examination, which required placing Nick under general anesthesia. Nick went into cardiac arrest while under anesthesia, and despite every effort to resuscitate him, staff were unable to revive Nick. A final pathology report will provide more information in the coming weeks.

American Trail keeper Victoria Adams described Nick as being a charming and fun individual to work with. “Nick was such a delightful sea lion to see and experience here at American Trail,” said Adams. “Visitors from all over were astonished to see how strong and smart he was and see his unique variety of special training behaviors.”    

A true ambassador for his species, Nick's personality and size—more than 700 lbs. during breeding season—made him popular with visitors, providing them with an opportunity to learn about an iconic North American species and what steps they can take to protect marine wildlife.

“Nick was such a sweet and silly sea lion,” said Katelyn Stache, assistant curator of carnivores at Denver Zoo Conservation Alliance (DZCA). “Even with his large size, he was incredibly patient and seemed unaware of just how big he was — which made him the perfect animal to help teach many of us how to work with sea lions. He knew so many different behaviors on cue, but his vocalizations were always my favorite. I’m really going to miss his funny grin and seeing the trust he shared with his caretakers. What a special boy.”    

Born in the wild, Nick was found alone in Laguna Beach, California as a newborn with his umbilical cord still attached. He was rescued and hand-reared by the Pacific Marine Mammal Center, who cared for him until he was 10 months old. Because of his reliance on human caretakers, Nick was deemed to be unreleasable, and transferred to the DZCA in Denver, Colorado. He moved to NZCBI on Oct. 6, 2023, to be temporarily housed until DZCA complete renovations to the sea lion habitat. He made a big splash when he arrived in Washington, D.C., impressing visitors with his large personality, unique dance moves and booming bark. Nick was expected to return to DZCA later this year.  

According to the team at DZCA, Nick’s legacy lives on through his two offspring who still call DZCA home, Gunnison and Ady, his mate, Luci, and the countless human lives he touched during his lifetime.    

Although considered “of least concern” on the International Union for Conservation of Nature’s Red List, wild California sea lions face dangers such as human conflict and ocean pollution. Those interested in helping protect marine mammals can consider reducing their use of single use plastics and recycling, when possible, as well as choosing sustainably source seafood.