The effects of oil contamination and cleaning on sea otters (Enhydra lutris), I. Thermoregulatory implications based on pelt studies

Abstract

The contamination of sea otter (Enhydra lutris) fur with crude oil or dispersants reduces its insulation and could subject the animal to hypothermia. This study tested methods for removing crude oil from sea otter pelts, and measured changes in insulation caused by oil contamination and subsequent cleaning. Four detergents and two pretreatments were tested on sea otter pelts soiled with fresh crude, 5-day weathered crude, and an oil–dispersant (COREXIT 9527) solution. To examine the effects of oiling and cleaning on the thermal properties of the fur, the thermal conductance of untreated, oiled, and cleaned pelt samples was determined with a heat-flow transducer. Changes in lipid concentration in the fur resulting from contamination and cleaning were also assessed. The results demonstrated that Dawn dishwashing detergent was the most effective agent in removing crude oil from sea otter fur. This detergent removed similar amounts of oil with 15 or 40 °C rinse water, and was less effective when used in conjunction with mineral oil or soap pretreatments. Oil contamination caused a two- to four-fold increase in thermal conductance over base-line levels (7.64 ± 1.30 W/(m2∙ °C)). Following cleaning, the thermal conductance of the pelt was not significantly different from that of untreated fur. However, mean lipid weight decreased from 7.4 mg lipid/g fur in untreated pelts to 2.0 mg lipid/g fur in cleaned pelts. This study demonstrated that even though natural oils may be lost during the cleaning process, proper cleaning and rinsing restores the water repellency of the sea otter pelt after exposure to crude oil.