A new UC Davis analysis finds that adult sea otters in California in 1998-2001 died in unusually high numbers from newly recognized diseases and in geographic clusters -- all of which suggest that their coastal environment may be so substantially altered that the species could be in jeopardy.
The findings are particularly worrisome in the wake of last week's report that a startling 100 southern sea otters have washed up dead on California beaches since January -- 100 deaths in a population that has been falling overall since 1995 and now stands at about 2,000.
The new analysis, done in collaboration with the California Department of Fish and Game, does not include those 100 otters, but its findings may help researchers understand their deaths.
"We are very concerned that the otters are dying so frequently of diseases. This indicates that the ecosystem is very unhealthy," said wildlife epidemiologist Jonna Mazet, director of the UC Davis Wildlife Health Center and leader of the campus' longstanding otter-research programs.
The new study identifies the most important causes of otter deaths in California and determines where otters are most at risk. It reviews 105 deaths of southern sea otters (Enhydra lutris nereis) -- all the beached carcasses found in California from February 1998 through June 2001, the most recent period for which complete data are available.
The lead analyst was Christine Kreuder, a veterinarian at the UC Davis Wildlife Health Center and a doctoral student in epidemiology. Her chief collaborator was Melissa Miller, a UC Davis wildlife veterinarian who has been performing otter necropsies for Fish and Game since 1998.
The researchers' key findings:
In a healthy population, juvenile and aged otters should account for most deaths. But the UC Davis/Fish and Game analysis found that the largest proportion of dead otters -- 47 percent -- were 4 to 9 years old. That is the age when the anima
Contact: Sylvia Wright
University of California - Davis