Oiled Sea Otter Rehabilitation Course

Release Alternatives

In addition to a no release alternative, there are four alternatives in release of rehabilitated sea otters: 1) release at the site of capture, 2) release in the general vicinity of capture, 3) relocation to an area already inhabited by sea otters, or 4) relocation to an area uninhabited by sea otters. Each will result in costs and benefits to sea otter conservation.

No Release

In terms of preventing the possible introduction of any domestic or exotic animal diseases into the wild sea otter population, the most conservative approach would be not to release the animals. If this decision is made, then the only alternatives are placing the animals in zoos, aquaria, or research facilities or to euthanize them. If the number of rehabilitated animals is small (ten or fewer), their placement in such facilities may be feasible. Although several facilities are willing to temporarily care for oiled or young sea otters on an emergency basis, most have little or no need for additional wild-caught sea otters. During the EYOS, thirty-seven sea otters, either because of age or health, required permanent care in captivity. Nine of these heavily oiled otters died in April 1989. Another 197 sea otters were rehabilitated to the point that release was recommended. Placement of that many animals in aquaria was impossible. Given the constraints of existing space, a no release alternative is feasible only if few animals are in need of placement. Clearly, permanently holding large numbers of sea otters would require construction of additional holding space. Euthanasia, although not a preferred option for healthy sea otters, must be considered for unwanted, impaired, or unhealthy animals.

Release at Capture Site

We assume in this discussion that only sea otters that are oiled will be captured and, therefore, that the capture sites will have been oiled or located adjacent to oiled areas. In many respects, the release of sea otters near their capture sites is preferred because the animals will be familiar with areas normally used for feeding, resting, pupping, and protection from inclement weather. However, release at capture sites could be precluded by contamination of local habitat. Although release at the point of capture may contribute to research objectives, it may not be in the best interest of the released animals. Barring such research, long-term holding of sea otters while the environment cleanses itself may be required if this option is selected.

Release in General Vicinity of Capture

Releasing sea otters in unoiled areas relatively close to the original capture sites (e.g., within 30-80 km) may minimize the detrimental effects of placing the animals in an unfamiliar area. If the animals are released into familiar habitat, they may remain in the area, thereby enhancing their chances for surviva1. However, it may be difficult to keep the sea otters from reentering oiled areas. The relative benefits of releasing otters near their original capture sites, which may still suffer from oiling, to minimize relocation effects (see below) cannot be determined at this time. Certainly, the severity and geographical extent of the oil contamination would have to be considered. Assuming that damage to the habitat from oil is not extensive, release close to the original capture area may pose the lowest risk to individual animals.

Relocation to an Area Inhabited by Other Sea Otters

The risks of relocating sea otters into areas inhabited by other sea otters are not known. By relocation, we refer to transporting sea otters to areas outside of their home range. Home ranges of sea otters vary in size and are not known with certainty. However, radio telemetry studies of sea otters suggest that the maximum extent of their home range can be measured in tens of kilometers, as opposed to hundreds or thousands of kilometers. Information on the success of relocations comes largely from programs to reestablish populations in areas where sea otters were historically found (Jameson et a1., 1982; Rathbun et a1., 1990). Relocation and release into areas already occupied by sea otters may minimize the detrimental effects of relocation and ensure that the area is generally capable of supporting them. However, the risk of disease transmission is higher.

Release into an area already occupied by sea otters does not guarantee a favorable response from the public, especially if commercial, subsistence, or recreational fishing operations are potentially affected (Rappoport et a1., 1990). Moreover, relocated sea otters may not stay in the vicinity of the release site. Evidence from Ralls et al. (1992) and Monnett et al. (1990) indicate that some relocated sea otters may travel hundreds of kilometers to return to the vicinity of their capture.

Relocation to an Area Not Inhabited by Sea Otters

Many efforts have been made to transplant sea otters into uninhabited areas, and although the factors involved are not understood, high rates of mortality and disappearance of those animals are typical (Jameson et a1., 1982). The 1989-1991 transplant of southern sea otters to San Nicolas Island in California is a good example. Of the 139 sea otters relocated, only about 12 remained there. At least 10 of the otters died, and a minimum of 31 are known to have returned to the mainland population, a distance of more than 300 km. The remaining sea otters disappeared and are unaccounted for (USFWS, unpublished data). Relocating sea otters, even to areas with abundant food resources, places those animals at increased risk. Within Alaska, because of expansion of natural populations and previous transplant efforts, areas of suitable, unoccupied sea otter habitat are scarce. Release in these areas would likely involve relatively long-distance relocations. Moreover, conflicts with the public may occur if sea otters are released into areas with high shellfish densities which are harvested in commercial, subsistence, and recreational fisheries. Release of sea otters into unoccupied food-rich habitats will likely result in an adverse reaction from some segments of the public.