Abstract
Domoic acid (DA) toxicosis is an important cause of mortality in sea otters, yet little is known about the clinical signs and effects of DA exposure in live sea otters. In 2017, two adult male southern sea otters were rescued due to malnutrition and neurologic signs. The first otter stranded on May 31 in Morro Bay, CA (otter 1) and the second on July 3 in Half Moon Bay, CA (otter 2). High levels of DA were found in the feces of otter 1 upon admission to The Marine Mammal Center for rehabilitation. MRI scans showed mild unilateral (right) atrophy of the hippocampus in otter 1 and severe unilateral (left) hippocampal atrophy in otter 2, both consistent with lesions commonly found in sea lions with DA toxicosis. Otter 1 also had an elevated titer to Toxoplasma gondii, and was treated with trimethoprim/sulfamethoxazole for 30 days. A life history tag (LHX) and VHF tag were implanted intra-abdominally to monitor the otters’ location, post-surgery internal temperature, and long-term survival. After four months of supportive care and rehabilitation, the otters were released in the same locations that they originally stranded. Location and behavioral data were collected daily for 30 days post-release for otter 1, who remained resident to the release site. This otter exhibited normal behavior for two months post-release before becoming acutely ill and dying from complications of disseminated coccidioidomycosis. Otter 2 did not show resident behavior and within 7 days of release had traveled 50 mi (80 km) north in Point Reyes National Seashore and has been sighted opportunistically thereafter through January 27, 2018. These cases demonstrate the ability to diagnose, rehabilitate, and release sea otters affected by DA toxicosis, and will help define the clinical signs and potential impact of DA on sea otter populations.
Acknowledgements
We thank Michelle Staedler, Andy Johnson, and Marissa Young, RVT from the Monterey Bay Aquarium for support and training The Marine Mammal Center staff and volunteers in post-release observations and implant surgery and the dedicated response, animal care volunteers and staff, and necropsy staff at The Marine Mammal Center and California Dept. of Fish & Wildlife for their excellent rescue, animal care, post-release monitoring, and laboratory assistance.
* Presenting author