Abstract
The primary means of removing oil from sea otters (Enhydra lutris) is washing them in dilute detergent with prolonged rinsing in warm water, forced air drying, and recovery with variable access to sea water.1 Sea otter body temperatures normally vary over a range of at least 2°C; however, both hypo- and hyperthermia have been problems previously observed when otters are captured, anesthetized, and washed. Male southern sea otters deemed non-releasable by U.S. Fish and Wildlife Service were obtained and trained for medical and sampling behaviors, equipped with temperature-monitoring devices, and washed in the same manner as they would be if oiled. A reductionist approach was used to try and isolate the effects of each stage in the washing procedures. Anesthesia alone resulted in a modest core temperature elevation. Temperature of rinse water (27°C and 32°C tested) made little difference in the rate of core body temperature loss, but did influence the depth of temperature depression. Otters exhibited significant behavioral changes after washing, primarily greatly increased grooming and time out of water. By providing washed sea otters with access to warmed or ambient temperature soft fresh water, very significant improvements were seen in otters’ grooming behaviors, core body temperature stability, subcutaneous temperature stability, return of coat insulating patterns as measured by visual and infrared imaging, as well as reduced caloric requirements to maintain base body weight. These improvements resulted in an approximately 50% reduction in the time required for recovery to a defined normal baseline. Based on electron micrographic imaging of river otter pelts, it appears that scales and shafts of the hair form interlocking watertight plates that trap air against the skin and keep water out. Physical interlocking and electrostatic forces are believed to help hold these plates together, and it appears that salt crystals and soap scum left on sea otter underfur hairs using previously accepted washing methods interfere with this. It appears that several simple and relatively inexpensive improvements in methods used to wash sea otters could greatly reduce the time required for recovery, thus the stress, labor and expense associated with washing oiled sea otters. This could also improve recovery and survival of oiled free-ranging sea otters and reduce costs, a source of some controversy, in the event another catastrophic oil spill occurs in coastal waters of Eastern Siberia, Alaska, the Pacific Northwest or California that support sea otter populations. Major oil extraction, shipping, transit, and refinery operations occur and are planned for these areas, and the western Alaskan and California sea otter populations are listed as threatened under the Endangered Species Act of 1973.
Literature Cited
1. Williams T.M., and R.W. Davis. 1995. Emergency Care and Rehabilitation of Oiled Sea Otters. University of Alaska Press.