The thermoregulatory and metabolic consequences of external contamination have been well documented for oiled sea otters (Costa and Kooyman, 1982; Williams et al., 1988; Davis et al., 1988). In contrast, there has been little evidence of toxicological effects following crude oil exposure in these marine mammals. Geraci and Williams (1990) reviewed the effects of accidental spills and experimental oiling on sea otters and found little indication of organ damage. In several spills involving wild river otters (Lutra lutra, Lutra canadensis), it was not possible to correlate the cause of death with oil contamination (see Chapter 15).
With so little information about the systemic effects of oil on sea otters, it has been difficult to determine the cause of the high mortality in otters contaminated during the Exxon Valdez oil spill (EVOS). Moreover, the effects of external oiling are not easily distinguishable from the possible toxicological effects of hydrocarbon exposure. The purpose of this chapter is to evaluate the primary factors that may contribute to mortality in oiled sea otters. Specifically, the physical and chemical effects of oil exposure and the stress of capture and rehabilitation are discussed. The conclusions of this chapter are based primarily on data from wild sea otters captured for rehabilitation or found dead on beaches following the EVOS. Clinical evaluations, necropsy results, histopathologic assessments, and tissue residue analyses were used to evaluate the cause of death. Because tissues taken during necropsy are critical for these investigations, we first review the procedures for tissue sample collection and storage, histopathology, and toxicology.
