Abstract

The southern sea otter (Enhydra lutris nereis) was listed as “threatened” under the Endangered Species Act (ESA) in 1977 and, despite 25 years of protection and efforts to foster recovery, they remain well below the threshold for delisting. Some populations of northern sea otters (Enhydra lutris kenyoni) are in the process of being listed under ESA following recent sharp and poorly understood population declines. Persistent organic pollutant (POP), disease exposure and overall health data was derived from apparently healthy free-ranging sea otters captured in Monterey Bay California from 1998–2000. Similar data was derived from several populations of Alaskan sea otters in 1997. Age, sex, and location appear to exert significant influence on POP and disease exposure. In general, southern sea otters have higher levels of accumulated POPs, with the exception being some specific locations in Alaska where military dumping is known to have occurred. POPs appear to accumulate with age in both males and females and reach highest levels in adult males. Pregnancy followed by pupping results in sharp drops in POP burdens of female southern sea otters, probably as a result of lactational transfer. Patterns of disease exposure are very different for Alaskan and California sea otters, and in some locations, differences in disease and POP exposure may influence the health of sea otters, patterns of mortality, and population demographics. Conservation strategies for northern and southern sea otter populations need to reflect these findings.