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Article History

Received: 9 April 2026

Accepted: 1 July 2026

First Online: 7 July 2026

Declarations

:

: Serum samples from southern sea otters included in this study were obtained from animals recovered through authorized stranding response by the California Department of Fish and Wildlife (CDFW), and/or rehabilitation of animals that initially stranded alive by The Marine Mammal Center (TMMC), and Monterey Bay Aquarium (MBA). All handling protocols were approved through applicable federal permits and regulatory authorizations as detailed below. Animals included in this study consisted of stranded free-ranging southern sea otters that were found dead, died during care, or were humanely euthanized when necessary for animal welfare reasons; no animals were euthanized specifically for the purposes of this research.

: CDFW handled stranded sea otters under Sect.  109(h) of the U.S. Marine Mammal Protection Act (MMPA), in accordance with U.S. Fish and Wildlife Service (USFWS) regulations implementing the MMPA (50 CFR 18.22[a]) and the U.S. Endangered Species Act (50 CFR 17.21[c][3]). TMMC and MBA conducted animal recovery, rehabilitation, humane euthanasia, and sample collection under USFWS permits MA101713-1 and PER4324646 (TMMC), and MA032027 and MA186914 (MBA), respectively. These statutes and permits authorize wildlife agencies and rehabilitation centers to intervene on behalf of free-ranging marine mammals for their protection and welfare, including rehabilitation and humane euthanasia when indicated. All animal handling and euthanasia procedures were conducted under standardized institutional animal care and veterinary oversight protocols, and gross necropsies were performed on all sea otters by veterinary pathologists and trained staff at CDFW and TMMC. Serum and other biological samples were collected from fresh or previously frozen/thawed carcasses during postmortem examination.

: Not applicable.

: The authors declare no competing interests.