Alas, today’s post is about a sad event that happened recently, but is nonetheless important to share: Otto, the southern sea otter we had previously posted about, died on December 19th. His body was recovered floating in Morro Bay, California.
As we previously reported, Otto was one of two southern sea otters recently taken to The Marine Mammal Center in Sausalito, California. Both otters were suffering from symptoms of domoic acid toxicosis (referred to as amnesic shellfish poisoning in humans), and were released after completion of rehabilitation. Otto and Yankee Doodle, the second otter, were notably the first two otters released back into the wild with two telemetry transmitters surgically implanted: a Life History Transmitter (or LHX tag) and a VHF transmitter beacon.
Until fairly recently, both animals were doing well after their release. However, in early December Otto was spotted acting abnormally, and his body condition had declined. Senior Biologist Mike Harris from the California Department of Fish and Wildlife Office of Spill Prevention and Response (CDFW OSPR) and volunteers from the Center repeatedly attempted to rescue him, but he evaded capture. After his body was discovered, it was transported to the CDFW OSPR Marine Wildlife Veterinary Care and Research Center in Santa Cruz for postmortem examination.
The necropsy was performed by CDFW OSPR pathologist Melissa Miller, her necropsy team and The Marine Mammal Center’s chief pathologist Padraig Duignan, research assistant Barbie Halaska, and visiting resident pathologist Norbert van de Velde. Otto’s cause of death was drowning. His lungs and airways were filled with seawater and body fluids. However, microscopic examination of tissue impression smears and positive fungal culture confirm that the drowning was the result of complications from coccidioidomycosis, an infection caused by the fungus Coccidioides immitis. This infection, more commonly known as Valley Fever, was widespread in his body with involvement of his lungs and pleura (a thin layer of tissue that protects and cushions the lung), as well as most of his lymph nodes and his spleen.
Almost all cases of coccidioidomycosis in animals and people are environmentally acquired (inhaled). Prior scientific studies have shown that Otto’s home range in San Luis Obispo County, California, is endemic for Coccidioides immitis, and local exposure through inhalation is the most likely source of his infection. This naturally occurring fungus is not easily transmitted between infected individuals. The main risk for people would be from cutting or injecting themselves while handling infected carcasses or tissues, or from handling severely decomposed, infected animals where the risk of inhalation of fungal spores could be present. Staff at CDFW OSPR and The Marine Mammal Center are trained to employ extra precautions when caring for, recovering, or performing postmortem examinations on stranded wildlife. Members of the public should always ask for help from these trained experts rather than handle live or dead sea otters themselves.
Given that visibly enlarged lymph nodes were documented in photographs taken in the field soon after release September 2017 (see photo above), there is a possibility that Otto was already infected and in the earlier stages of coccidioidomycosis when he first came into captive care in June 2017, even though he did not display any clinical signs of infection during his period of rehabilitation. Although the period from fungal infection to clinical disease is unknown for sea otters, this fungus is capable of causing chronic, slowly progressive disease.
During the necropsy, the two implanted tags were removed. The tags were both found free-floating, as should be, with no signs of adhesion or entrapment. The site of the surgical incision was unremarkable. After sanitizing the tags to remove or kill any bacteria, virus or fungal spores, Tenaya Norris and other scientists from The Marine Mammal Center conducted some testing with the LHX tag, which was then sent to the Alaska SeaLife Center in Seward, AK, for a more detailed analysis of the tag and any additional data not transmitted. Since the LHX tag was removed from the host body during necropsy, its normal sequence of operations was altered. LHX tags transmit a condensed, processed subset of all the data stored since implantation, and physical access to the tag allows the downloading of additional data not previously transmitted. So, standby for an upcoming and more detailed report about what we will still learn from the pathology report and the data recovered from the LHX tag.
Though expected, it is good news that the preliminary necropsy revealed no indication that the two implants or the surgery were in any way connected to Otto’s death.
And happily, we can report that Yankee Doodle continues to do well, and was recently spotted by kayakers eating crab near Point Reyes:
The rehabilitation and research referenced above was conducted under USFWS permit #MA101713-1.
Written by Markus Horning with Melissa Miller.
Featured Image: Eight-year-old southern sea otter Otto rests in a pool during rehabilitation at The Marine Mammal Center in Sausalito, CA. The male otter was rescued by trained responders from the Center’s San Luis Obispo Operations in Morro Bay, CA. Photo Credit Dana Angus © The Marine Mammal Center.