The Effects of Oil on Wildlife

We have all seen pictures and videos of wildlife covered in black, sticky oil after an oil spill.  These pictures are usually of oiled birds.  Many people are not aware that it is not just birds that get oiled during a spill.  Other marine life such as marine mammals can also suffer from the effects of an oil spill.  Even small spills can severely affect marine wildlife.

Not all oils are the same.  There are many different types of oil and this means that each oil spill is different depending on the type of oil spilt.  Each oil spill will have a different impact on wildlife and the surrounding environment depending on:

• the type of oil spilled,
• the location of the spill,
• the species of wildlife in the area,
• the timing of breeding cycles and seasonal migrations,
• and even the weather at sea during the oil spill.

Oil affects wildlife by coating their bodies with a thick layer.  Many oils also become stickier over time (this is called weathering) and so adheres to wildlife even more.  Since most oil floats o nthe surface of the water it can effect many marine animals and sea birds.  Unfortunately, birds and marine mammals will not necessarily avoid an oil spill.  Some marine mammals, such as seals and dolphins, have been seen swimming and feeding in or near an oil spill.  Some fish are attracted to oil because it looks like floating food.  This endangers sea birds, which are attracted to schools of fish and may dive through oil slicks to get to the fish. Oil that sticks to fur or feathers, usually crude and bunker fuels, can cause many problems.  Some of these problems are:

• hypothermia in birds by reducing or destroying the insulation and waterproofing properties of their feathers;
• hypothermia in fur seal pups by reducing or destroying the insulation of their woolly fur (called lanugo).  Adult fur seals have blubber and would not suffer from hypothermia if oiled.  Dolphins and whales do not have fur, so oil will not easily stick to them;
• birds become easy prey, as their feathers being matted by oil make them less able to fly away;
• marine mammals such as fur seals become easy prey if oil sticks their flippers to their bodies, making it hard for them to escape predators;
• birds sink or drown because oiled feathers weigh more and their sticky feathers cannot trap enough air between them to keep them buoyant;
• fur seal pups drown if oil sticks their flippers to their bodiesk
• birds lose body weight as their metabolism tries to combat low body temperature;
• marine mammals lose body weight when they can not feed due to contamination of their environment by oil;
• birds become dehydrated and can starve as they give up or reduce drinking, diving and swimming to look for food;
• inflammation or infection in dugongs and difficulty eating due to oil sticking to the sensory hairs around their mouths;
• disguise of scent that seal pups and mothers rely on to identify each other, leading to rejection, abandonment and starvation of seal pups; and
• damage to the insides of animals and birds bodies, for example by causing ulcers or bleeding in their stomachs if they ingest the oil by accident.

Oil does not have to be sticky to endanger wildlife.  Both sticky oils such as crude oil and bunker fuels, and non-sticky oils such as refined petroleum products can affect different wildlife.  Oils such as refined petroleum products do not last as long in the marine environment as crude or bunker fuel.  They are not likely to stick to a bird or animal, but they are much more poisonous than crude oil or bunker fuel.  While some of the following effects on sea birds, marine mammals and turtles can be caused by crude oil or bunker fuel, they are more commonly caused by refined oil products.

Oil in the environment or oil that is ingested can cause:

• poisoning of wildlife higher up the food chain if they eat large amounts of other organisms that have taken oil into their tissues;
• interference with breeding by making the animal too ill to breed, interfering with breeding behaviour such as a bird sitting on their eggs, or by reducing the number of eggs a bird will lay;
• damage to the airways and lungs of marine mammals and turtles, congestion, pneumonia, emphysema and even death by breathing in droplets of oil, or oil fumes or gas;
• damage to a marine mammal's or turtle's eyes, which can cause ulcers, conjunctivitis and blindness, making it difficult for them to find food, and sometimes causing starvation;
• irritation or ulceration of skin, mouth or nasal cavities;
• damage to and suppression of a marine mammal's immune system, sometimes causing secondary bacterial or fungal infections;
• damage to red blood cells;
• organ damage and failure such as a bird or marine mammal's liver;
• damage to a bird's adrenal tissue which interferes with a bird's ability to maintain blood pressure, and concentration of fluid in its body;
• decrease in the thickness of egg shells;
• stress;
• damage to fish eggs, larvae and young fish;
• contamination of beaches where turtles breed causing contamination of eggs, adult turtles or newly hatched turtles;
• damage to estuaries, coral reefs, seagrass and mangrove habitats which are the breeding areas of many fish and crustaceans, interfering with their breeding;
• tainting of fish, crustaceans, molluscs and algae;
• interference with a baleen whale's feeding system by tar-like oil, as this type of whale feeds by skimming the surface and filtering out the water; and
• poisoning of young through the mother, as a dolphin calf can absorb oil through it's mothers milk.

  Animals covered in oil at the beginning of a spill may be affected differently from animals encountering the oil later.  For example, early on, the oil maybe more poisonous, so the wildlife affected early will take in more of the poison.  The weather conditions can reduce or increase the potential for oil to cause damage to the environment and wildlife.  For example, warm seas and high winds will encourage lighter oils to form gases, and will reduce the amount of oil that stays in the water to affect marine life.

The impact of an oil spill on wildlife is also affected by where spilled oil reaches.  For example, fur seal pups are affected more than adults by oil spills because pups swim in tidal pools and along rocky coasts, whereas the adults swim in open water where it is less likely for oil to linger.  Dugongs als feed on seagrass along the coast and therefore be more affected by oil spills.

Different resources will be needed to combat an oil spill, depending on the number and type of wildlife that is affected.  Quick and humane care of wildlife affected by oil spills is required by law.  The National Oiled Wildlife Response guidelines [ PDF: 126KB] have been developed at both the Commonwealth and State/Territory level under Australia's national strategy to respond to oil and chemical spills in the marine environment.  This strategy is known as the National Plan to Combat Pollution of the Sea by Oil and other Noxious and Hazardous Substances (National Plan).