Effects on Wildlife

Effects of Oil

Oil, through simple physical contact, inhalation, ingestion and absorption have demonstrated harmful effects on wildlife. These effects include, but are not limited to, contamination of feathers and fur, and damage to vital organ systems, including: the lungs and air sacs, kidneys, liver, heart, blood, and gastrointestinal tract.

Rehabilitation of oiled wildlife focuses primarily on the adverse physiological effects of oil on individual animals. These effects, while complex, can often be successfully counteracted through the cooperative efforts of veterinarians, biologists and rehabilitators with oil spill response experience. The primary objective of wildlife rehabilitation is to care for injured animals and release them to their natural environment. Rehabilitation efforts can be particularly important when endangered or threatened species are contaminated.

The following information presented focuses on the effects and rehabilitation of birds, although Tri-State treats a wide range of oil-contaminated wildlife including mammals & reptiles. In general, the effects of oil on birds can be characterized as environmental, external, and internal.

Environmental Effects

Environmental effects are perhaps the broadest category of the effects of oil on wildlife. Environmental effects include, but are not limited to: immediate contamination of the regional food source; reduction in the breeding animals and plants that provide future food sources; contamination of nesting habitat, and reduction in reproductive success through contamination and reduced hatchability of eggs or temporary disruption of ovarian function. Secondary contamination of nests, eggs, young, other flock members and predators is also common.

External Effects

The external effects of oil are the most noticeable and most immediately debilitating. Birds that are frequently affected by oil spills include those that remain on the water, such as ducks, loons, and grebes, and those that feed in the water, such as gulls, terns, herons, and birds of prey including bald eagles and ospreys. Oil can contaminate the entire bird or only parts of the bird, depending on the amount of oil in the water and the bird’s natural behavior (swimming, wading, diving) in the water. Oil, by disrupting the interlocking structure of feathers, destroys the waterproofing and insulating properties of plumage. The oiled bird may suffer from chilling, may be unable to fly, or may be unable to remain afloat in the water. A bird’s direct contact with oil components can result in chemical burns and the absorption of toxic chemicals through its skin. Depending on the degree of impact, an oiled bird may have difficulty obtaining food or escaping predators. The decreased foraging ability of the animal, combined with the presence of oil in the environment, usually results in a loss of attainable food sources. It is these external effects of oil on birds that are most often recognized by the general public and the image of an oil soaked animal elicits a tremendous emotional response in humans. Although well intentioned, many inexperienced responders attempt to treat the external effects or remove the oil from the feathers without first addressing the critical internal effects (discussed below).

Internal Effects

The internal effects of oil on birds, while not as apparent as the external effects, are equally life-threatening. Direct toxic effects on the gastrointestinal tract, pancreas and liver have all been documented. Ingestion of oil by birds attempting to clean feathers through preening frequently results in injury to the gastrointestinal tract. This damage prevents the animal’s digestive system from utilizing food or water, causing the animal to become progressively weaker in a very short time. A similar irritation of other mucosal surfaces can lead to ulceration of eye surfaces, and the moist surfaces inside the mouth. Kidney damage, a common finding in oiled birds, is believed to occur both as a direct effect of the toxins in the oil and secondary to severe dehydration. Dehydration and decreased body temperatures are medical emergencies and can result in clinical shock and eventual loss of life. As an oiled bird becomes more debilitated, its immune system is compromised and the bird becomes susceptible to secondary bacterial and fungal infections which are potentially life-threatening.

Rapid retrieval of oiled wildlife and proper medical stabilization and evaluation by veterinarians and licensed wildlife rehabilitators experienced in the treatment of oiled wildlife are critical to the success in caring for oiled animals. Once the internal effects of the oil have been addressed, then an experienced team of rehabilitators will work quickly and quietly to gently remove the oil from the feathers of the bird. Special wildlife rehabilitation techniques, which are geared towards reducing the stress of captivity and providing a healthy environment for recovery, are employed until the animal is ready for release.


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