Exposure to oil (petroleum) can result in both external and internal damage to animals. It has the greatest impact on

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

species, aquatic

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s, and other aquatic organisms. Affected wildlife can usually be identified via visual inspection, and can be treated if found early on. Major sources of such oil in the environment include accidental

oil spills An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

from off-shore sites,

oil tankers An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined crud ...

, pipelines, and other facilities that store and process oil.

Cause

The main cause of wildlife exposure to oil is

oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

s. Oil spills occur most commonly near oil-shipping routes, pipelines, wells and refineries. Oil spills have a more drastic impact in the late winter and early spring months, because large populations of overwintering birds gather near shores. The

Deepwater Horizon Oil Spill The ''Deepwater Horizon'' oil spill (also referred to as the "BP oil spill") was an industrial disaster that began on 20 April 2010 off of the coast of the United States in the Gulf of Mexico on the BP-operated Macondo Prospect, considered ...

(also known as the BP Oil Spill) was estimated to have killed over 8,000 birds, sea turtles and marine mammals from April to September in 2010. Animals come into direct contact with the oil, and may ingest, inhale or absorb it. Animals may also become contaminated by eating other contaminated animals.

Species affected

Any animal can come into direct contact with an oil spill. However, marine species are more likely to be impacted by an oil spill.

Birds

Of the many species affected by direct exposure to oil, birds are usually the most severely affected. Birds that nest near the shoreline are most likely to be affected, including

loon Loons (North American English) or divers (British / Irish English) are a group of aquatic birds found in much of North America and northern Eurasia. All living species of loons are members of the genus ''Gavia'', family Gaviidae and order Gavi ...

s (''Gavia'' spp.),

grebe Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...

s (Family: Podicipedidae),

murres ''Uria'' is a genus of seabirds in the auk family known in Britain as guillemots, in most of North America as murres, and in Newfoundland and Labrador as turr. These are medium-sized birds with mainly brown or black plumage in the breeding sea ...

(''Uria'' spp.),

pelican Pelicans (genus ''Pelecanus'') are a genus of large water birds that make up the family Pelecanidae. They are characterized by a long beak and a large throat pouch used for catching prey and draining water from the scooped-up contents before s ...

s (Family: Pelecanidae), and

penguin Penguins (order (biology), order List of Sphenisciformes by population, Sphenisciformes , family (biology), family Spheniscidae ) are a group of Water bird, aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: on ...

s (Family: Spheniscidae). The species of bird and the type of oil can vary the effects of oil exposure. Birds affected often die from

hypothermia Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe h ...

, starvation, exhaustion, or drowning. Birds exposed to oil become more susceptible to other diseases due to a reduced immunologic function. Birds can come into contact with oil through direct exposure, which leads to ingestion, inhalation, and absorption. Birds coated with oil lose the insulation and waterproofing properties of their feathers, and can also ingest oil during

preening Preening is a found in birds that involves the use of the beak to position feathers, interlock feather that have become separated, clean plumage, and keep ectoparasites in check. Feathers contribute significantly to a bird's insulation, waterp ...

. Bird that are coated with oil lose the ability to thermo-regulate, fly, and float on water. Ingestion of oil can result in lung, liver and kidney damage, often leading to death. The oil can also affect the eggs laid by affected females, often resulting in embryonic death or low birth weight. 5-20 microliters of oil can kill embryos if the egg comes into contact. Eggs laid prior to an oil spill can also become damaged if an affected animal sits on the nest.

Mammals

Mammals are affected by oil spills in many of the same ways birds are, including organ damage, immune system suppression, skin irritation, and behavioral changes. It generally affects terrestrial mammals that feed on other affected animals that are directly exposed to oil. This includes scavengers, such as raccoons and skunks. It affects a variety of marine mammals, including

sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of the weasel family, but among the small ...

s (''Enhydra lutris''),

whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

s (Order: Cetacea),

dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...

s (Suborder: Odontoceti),

seals Seals may refer to: * Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly: ** Earless seal, or "true seal" ** Fur seal * Seal (emblem), a device to impress an emblem, used as a means of a ...

(Clade: Pinnipedia), and

manatee Manatees (family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species ...

s (''Trichechus'' spp.). Sea otters are among the most susceptible of marine mammals, because the oil interrupts their ability to trap air within their fur for insulation.

Other animals

Other species, such as

marine turtles Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...

(Superfamily: Chelonioidea), fish, and

shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater envir ...

can also be adversely affected by oil spills. Sea turtles may become affected when they return to shores to lay eggs. Fish are impacted by the oil that is taken in by their gills and digestive system. Many species of shellfish can survive exposure to oil, but accumulate high levels in containment in their bodies. Oil in water can contaminate algae, plankton, and fish eggs, which in turn contaminate fish that feed on them.

Clinical signs

Animals affected externally by oil can often be seen or found via the smell. In some light, transparent oils may be difficult to detect visually. Animals can also be internally diagnosed via necropsy by identifying petroleum hydrocarbons in their fat, liver, or kidney tissues For damage assessments, the death of the animal must have occurred after the oil spill. The severity of damage directly correlates with the amount of oil spilled and the animal's exposure to oil. However, a small spill at a more sensitive season or environment may have more drastic impacts than a large spill in a less sensitive season or environment. External exposure to oil often leads to destroyed insulating fur or feathers, resulting in death from hypothermia. Contact with oil can also result in blindness, which impairs animals' ability to compete for food or to avoid predators. The ingestion of oil can cause a variety of internal problems. These include

anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...

, reproductive impairment, and damage to the stomach and intestines. These animals can also suffer from dehydration and

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...

, due to a decreased thermo-regulation.

Treatment

Animals affected by oil should be cleaned and allowed to recover from stress. Animals should be kept in a quiet and warm environment while they recover. Direct contact with oil or oiled wildlife can be hazardous to human health, so it is recommended that treatment be performed by people who have received training.

References

{{reflist Oil Spills Ocean pollution Ecotoxicology