USGS ScienceSearch

USGS · 1007986

Sea otter mortality from the Exxon Valdez spill: Evaluation of an estimate from boat-based surveys

Abstract

The Exxon Valadez oil spill killed large numbers of sea otters ( Enhydra lutris ) in Prince William Sound (PWS), Alaska, where the spill originated, as well as within the oil’s path along the coasts of the Kenai Peninsula and Kodiak Island. Sea otters attracted particular attention after the spill due to their public appeal (Batten 1990) and known vulnerability to oil (Costa and Kooyman 1982, Siniff et al. 1982, Davis et al. 1988, Williams et al. 1988). Extensive efforts were made to rescue and rehabilitate oiled otters at a resulting cost of ca. $80,000 per animal (Estes 1991). The argument that otters lost in the spill should be similarly valued made the estimate of mortality a matter of substantial concern to those involved in spill-related litigation or out-of-court settlements.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

David L. Garshelis, James A. Estes. 2006-08-26. Sea otter mortality from the Exxon Valdez spill: Evaluation of an estimate from boat-based surveys. https://doi.org/10.1111/j.1748-7692.1997.tb00640.x

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

Quantifying southern sea otter (Enhydra lutris nereis) reactions to a quadcopter drone in central California

Drones are useful for wildlife research and management, but they can cause disturbance and harassment to wildlife. Sea otters ( Enhydra lutris ) are candidates for drone-based observation and monitoring but are vulnerable to disturbance. No studies have evaluated drone effects on sea otter behavior, but based on prior disturbance studies, we hypothesized: (1) sea otters would exhibit behaviors indicating higher reactivity in the presence of drones than when drones were absent and (2) drone disturbance to sea otters would be greater when drones were closer. At two sites in Monterey Bay, CA, we conducted 37 observational sessions, recording behavior codes for focal sea otters during a baseline (no drone) period and three consecutive drone flights. Data were analyzed using ANOVA and ordinal logistic regression models. At both locations, focal sea otters had higher behavior codes during drone trials compared to baseline, and behavior codes increased with descending drone altitude. Pup presence, group size, flight trial number, and gull presence were significant covariables. We calculated multipliers to predict drone-mediated behavioral responses at a range of drone altitudes. Our findings can inform best practices for a variety of uses of drones around sea otters, including population monitoring, oil spill response, and drone photography/videography.

California

Effects of feeding and habitat on resting metabolic rates of the Pacific walrus

Arctic marine mammals live in a rapidly changing environment due to the amplified effects of global warming. Pacific walruses ( Odobenus rosmarus divergens ) have responded to declines in Arctic sea-ice extent by increasingly hauling out on land farther from their benthic foraging habitat. Energy models can be useful for better understanding the potential implications of changes in behavior on body condition and reproduction but require behavior-specific metabolic rates. Here we measured the resting metabolic rates (RMR) of three captive, adult female Pacific walruses through breath-by-breath respirometry when fed and fasted resting out of water (sitting and lying down) and while fed resting in water. RMR in and out of water were positively related with pretrial energy intake when not fasted and 25% higher than RMR when walruses were fasted and out of water. Overall, RMR was higher than previously estimated for this species. Fasting RMR out of water was only 25% lower than subsurface swimming metabolic rates suggestive of relatively efficient swimming in adult females. Our results identify the importance of considering feeding status and species-specific differences in affecting metabolic costs. Further research is needed to better understand potential energetic costs of thermoregulation at temperatures experienced by wild walruses.

Valencia