Oiled Sea Otter Capture Course

Assessment of Impact and Strategy

An oil spill that impacts marine mammals is a major media event, placing considerable pressure on wildlife managers and biologists to act with minimal time for adequate preparation and planning. Yet, the assessment and strategy planning component of any operation will determine the ultimate efficacy of the action taken. It is imperative that the aims of the rescue effort are clearly set. Any marine mammal rescue program must also take into account several important aspects of the species’ behavior and life history; these will dictate what can and should be done.

Pinnipeds and polar bears are amphibious animals with haulout patterns that vary seasonally. The threat of oil fouling will differ depending on whether the animals are in the marine or terrestrial phase of their life cycle. During the pelagic phase, the animals may simply abandon the area to avoid the disturbance associated with clean-up activities. At other times of the year, some species of pinnipeds spend several weeks on shore without entering the water thereby also avoiding exposure. The situation is more serious when animals are regularly crossing between land and sea through a transition zone that tends to accumulate oil. Pinnipeds are usually gregarious while on shore; any impact is therefore likely to be localized and involve many animals of all ages. The magnitude of the problem will vary enormously depending on how approachable, tractable, and susceptible to disturbance the affected species is. In cases involving large terrestrial congregations, the rescue operation may cause greater perturbation than the oil itself. Here, the benefits of cleaning animals must be carefully weighed against the potentially negative effects of disturbing the colony. Pressure from public expectation should not be allowed to influence decisions. Unless there is strong evidence that the animals will soon become recontaminated, we believe that it is better to treat and release the animals on site rather than to subject them to the stress of relocation or prolonged confinement in a rehabilitation center.

In establishing a realistic set of goals for the rescue operation, it may be necessary to limit expectations and focus on what is achievable and most beneficial to the affected group or population. If large numbers and multiple-age classes of animals are impacted by oil, it is unlikely that the entire group can be captured for cleaning and treatment. Thus, when a colony of breeding seals is affected, efforts should be directed towards accessible animals such as pups of the year. It may also be appropriate to focus attention on reproductively active females, rather than males, to minimize mortality among the animals most important to the long-term health of a population.

With this approach in mind, the following information is necessary before any action is taken:

1) Approximate number of affected animals, their age, sex, physiological state (e.g. molting, lactating, pregnant), distribution, and degree of mobility between marine and terrestrial habitats.
2) Approximate number of animals at risk.
3) Accessibility of the affected area and the potential to remove the risk of further contamination.
4) Availability of equipment necessary to capture, clean, house (either temporarily or for ensuing transport), and treat the oiled mammals.

It is assumed that efforts to remove oil from the environment are underway concurrently, and that no attempt will be made to release cleaned and treated animals until the potential for recontamination has been minimized or eliminated.