Effects of the Exxon Valdez Oil Spill on River Otters

"Integration of individual-based and population-based studies is essential to understanding effects of pollution on populations and ecosystems. Here we provide an example of such integration from our exploration of effects on the Exxon Valdez oil spill (EVOS) on river otters (Lontra canadensis) inhabiting the terrestrial-marine interface in Prince William Sound, Alaska, USA. Our research was divided into 2 phases: an early phase (1989-92) immediately following the oil spill; and a late phase (1996-99), which focused on potential chronic effects of oil contamination in the Sound. We used a variety of measurements that considered the physiological status and health of individual river otters, as well as aspects of their ecology, behavior, and demography. We then conducted meta-analysis to explore interactions between individual-based and population-level data in demonstrating injury and subsequent recovery of otters from ill effects of EVOS. During both phases of our studies, we first conducted intensive research at 2 study sites, which we believed to be oil and non-oiled, and then expanded our investigations throughout similar areas of Prince William Sound. Nonetheless, our data are best interpreted as differences between heavily oiled areas and lightly oiled sites because later information indicated that our reference sites were lightly oiled. Thus we refer to heavily oiled sites as oiled and lightly oil sites as 'nonoiled'"--page 1.