The effects of oil contamination and cleaning on sea otters (Enhydra lutris). II. Metabolism, thermoregulation, and behavior

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Abstract
The purpose of this study was to develop a method to clean and rehabilitate sea otters (Enhydra lutris) that might become contaminated during an oil spill and to determine which physiological and behavioral factors were important in restoring the insulation provided by the fur. Tests were conducted on 12 sea otters captured in Alaska and brought to the Sea World Research Institute in San Diego. Measurements of average metabolic rate, core body temperature, behavior, and squalene (the major lipid of sebum) concentration on the fur were made under three conditions: (i) before oiling (base line), (ii) 1–3 days after 20% of the body surface area was covered with fresh crude oil, and (iii) after cleaning. Under base-line conditions in water at 13 °C, average metabolic rate was 8.0 W/kg, core body temperature was 38.9 °C, and whole body thermal conductance was 10.7 W/(m2∙ °C). Otters spent 35% of their time grooming, 45% resting, 10% swimming, and 10% feeding. The squalene concentration on the fur averaged 3.7 mg/g fur. Oiling increased thermal conductance 1.8 times. To compensate for the loss of insulation and maintain a normal core body temperature (39 °C), the otters increased average metabolic rate (1.9 times) through voluntary activity and shivering; the time spent grooming and swimming increased 1.7 times. Using Dawn detergent, we were able to clean the oiled fur during 40 min of washing and rinsing. Grooming activity by the otters was essential for restoring the water-repellent quality of the fur. Core body temperature, average metabolic rate, and thermal conductance returned to base-line levels 3–6 days after cleaning. Squalene was removed by cleaning and did not return to normal levels in the oiled area after 7 days. Veterinary care was important to keep the otters healthy. At least 1–2 weeks should be allowed for otters to restore the insulation of their fur and for recovery from the stress of oiling and cleaning.