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Introduction and General Information

The aim of oiled wildlife rehabilitation is to care for oiled individuals and, once they have recovered, to return them to their natural environment as members, or potential members, of the breeding population of their species. (B23.38.w2, P24.335.w12, D183.w6)

When an individual casualty is found oiled, or during a spill affecting only small numbers of wild animals, where sufficient resources, including staff time, are available to treat all casualties quickly and effectively, all oiled individuals (except those which are suffering greatly and should be immediately euthanased on humane grounds), can be treated, and there should be minimal delay in providing that treatment. (D214.2.w2, P62.2.w1)

In the circumstances of a large spill, when hundreds or thousands of individuals require care, cleaning and rehabilitation, it will not be possible to treat all individuals immediately and it may be impossible to give adequate treatment to all casualties. Therefore it is necessary to develop a system for triage, i.e. a systematic way to prioritise animals for treatment (B335.11.w11) and, sometimes, to decide quickly to euthanase some individuals in order to concentrate scarce or finite resources on other individuals. (D159.III.w3, D160.5.w5, D214.2.w2)

Even in a small spill, with resources not an issue, euthanasia may be the most humane choice for some individuals. (B23.38.w2, B188, D32.3.w3, D135.5.w5, D160.5.w5, D214.2.w2)


  • It is important that, if euthanasia/triage is required, the need for this is explained to volunteers. (D220)
  • Criteria for euthanasia, together with information about necessary consultation and authorisation, should preferably be agreed in advance of when they are required, made available in writing and displayed clearly so that all personnel are aware of them. (B363.App3.w16, V.w73)
  • Following euthanasia, the handling of the dead individual should be carried out in an appropriate manner, and processing of the casualty (e.g. progression to necropsy) should be carried out promptly. (B363.App3.w16, P14.6.w2)
  • A triage strategy, agreed by all stakeholders should be included within an oiled wildlife response contingency plan. (D183.w6)
    • Pre-determined triage criteria for field triage may be set down as written instructions. (P14.7.w30)

General considerations in triage and euthanasia

Factors which must be considered in triage include species, resources, and the welfare of the animals concerned. (D183.w6)

Prevention of unnecessary suffering:

  • Wild animals undergoing treatment and care are placed in a stressful situation.
    • For individuals with severe injuries, which would require extensive treatment and considerable handling of the casualty, immediate cessation of suffering by use of euthanasia may be the best choice for the individual. (P24.335.w12)
    • For individuals which will never be suitable for release back to the wild, euthanasia may be required to avoid unnecessary suffering. (P24.327.w4)


  • Resources may be limited. (D159.III.w3, D183.w6)
  • In the event of a large spill one of the resources likely to be limited is the time of skilled personnel. (D159.III.w3, J4.181.w3) If an individual oiled wildlife casualty requires an excessive additional amount of skilled time, this may compromise the survival of several other, less-severely injured individuals which could otherwise have received the less complicated care they required. (V.w5)
  • Facilities may also be a limited resource (D159.III.w3) and overcrowding reduces the chance of survival of casualties.
  • Even if it is decided that it will be possible to treat all individuals, it is unlikely to be physically possible to treat all individuals at one time; it will be necessary to prioritise and decide which individuals are to be treated first. (B335.11.w11)


  • Individuals of rare or endangered species, and those protected by international treaty, may be treated as a priority. (B363.8.w8, D160.5.w5)
  • Some species which are very highly vulnerable to stress in captivity may also be prioritised for treatment (e.g. divers (Gaviidae - Loons (Family))). (B188)
  • Loons, grebes (Podicipedidae - Grebes (Family)), seaducks etc., which have a tendency to develop Keel Lesions when maintained off water, should be prioritised for washing ahead of birds such as dabbling ducks and gulls, which can be successfully rehabilitated even after a longer period before washing. (P4.1990.w1)

Infectious disease:

  • An individual carrying an infectious disease is a risk to other individuals susceptible to that disease. 
    • Individuals with an infectious disease need to be isolated (B363.8.w8, D133.5.w5)
    • If isolation facilities (including personnel to look after individuals in such facilities) are not available, euthanasia may be required in order to avoid risking the spread of disease to other individuals.
    • Even when isolation facilities are available, for gregarious species it must be considered whether the time for which an individual must be placed in isolation is acceptable. (V.w5)
  • It is important to consider the feasibility of treating the individual diseased animal balanced against the risk of the disease spreading to the rest of the casualties. (D133.5.w5)
  • If an oil spill occurs during an infectious disease outbreak, it may be necessary to euthanase the oiled birds, rather than introduce the disease into a rehabilitation centre. (V.w78)

Time and development of secondary problems:

  • As a general rule, the longer a wildlife casualty is in care the greater the risk that it will develop a secondary problem associated with its captivity. (D135.9.w9)
    • Individuals which are not only oiled, but also have another problem requiring prolonged rehabilitation, are more likely to develop secondary problems. (D32.3.w3)
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Criteria for Euthanasia of Individual Casualties

Individual casualties may be euthanased to prevent unnecessary suffering. (B188, D32.3.w3, D135.5.w5, D160.5.w5, D214.2.w2) 
  • If euthanasia is required, then the decision should be made promptly and without prolonged debate: delaying causes unnecessary suffering and stress to the animal. (P24.335.w12)
    • Prompt decisions regarding euthanasia also avoid personnel suffering disappointment after putting in substantial effort of care and perhaps developing emotional attachment to the casualty. (P24.327.w4)

Note: criteria for euthanasia, together with information about necessary consultation and authorisation, should preferably be agreed in advance of when they are required, made available in writing and displayed clearly so that all personnel are aware of them. (B363.App3.w16, V.w73)

Conditions which are NOT considered to represent adequate conditions for euthanasia include:

  • Degree of oiling, even if very severe. (D32.3.w3, D135.7.w7, D159.III.w3, D160.App5.w13, D214.2.w2)
    • The length of time for which the casualty has been oiled and exposed to absorption of toxins is more likely to affect outcome. (B363.8.w8)
  • Temporary bleeding from the gastro-intestinal tract. (D32.3.w3, D135.7.w7, D159.III.w3, D160.App5.w13)
  • Moulting. (D32.3.w3, D135.7.w7, D159.III.w3, D160.App5.w13)
  • Reluctance to self-feed. (D135.7.w7)

Conditions in which euthanasia SHOULD be considered:

  • An individual with serious injuries which will require extended treatment or would make the individual unable to survive in the wild. (B23.38.w2, B363.App3.w16, D32.3.w3, D135.7.w7, D159.III.w3, D160.5.w5, D214.2.w2, J29.8.w1) This includes:
    • Beak injuries. (D32.3.w3, D160.5.w5, D160.App5.w13)
    • Limb fractures, particularly involving or near to a joint, and compound fractures which are oil contaminated. (B23.38.w2, D32.3.w3, D160.5.w5 D160.App5.w13)
    • Limb amputation. (J29.8.w1)
    • Extensive soft tissue injury. (D32.3.w3, D160.5.w5, D160.App5.w13); 
      • It may be difficult to adequately clean and treat large wounds which have been contaminated with oil. (B23.38.w2, B284.18.w18)
    • Blindness or significant visual or auditory defects. (D32.3.w3, D160.5.w5, D160.App5.w13, J29.8.w1)
  • An individual with signs of chronic disease (B363.8.w8) such as emaciation with prominent keel and wasted pectoral muscles. (D32.3.w3, D135.7.w7) However:
    • The keel is normally prominent in some species such as herons and egrets (Ardeidae - Heron, Bitterns, Egrets (Family)). (D32.3.w3, D135.7.w7, D160.App5.w13)
    • At the end of winter or following migration it is common for birds to have reduced muscle mass without this indicating any underlying disease process. (D32.3.w3, D135.7.w7, D160.App5.w13)
    • Individuals which are severely dehydrated may be very underweight, but rapidly gain weight when rehydrated. (D135.7.w7, D160.App5.w13)
  • Individuals showing signs of infectious disease. (B363.App3.w16, D32.3.w3, D159.III.w3); infectious disease unresponsive to treatment. (J29.8.w1)
    • These birds should be isolated and supported pending diagnosis, or euthanased and necropsied. (B23.38.w2, B363.8.w8, D135.7.w7, D160.App5.w13)
    • Individuals with warty lesions suggestive of avian pox should be isolated. (D160.App5.w13)
    • Other signs suggesting infectious disease include: bloody or mucous discharge from the eyes, nostrils or mouth; gurgling/moist respiratory sounds; watery or bloody diarrhoea, regurgitation, rapid loss of weight, pronounced neurological signs. (D135.7.w7, D160.App5.w13)
    • Note: if individuals with chronic infectious disease are released, they may transmit that disease to the wild population. (J29.8.w1)
  • Individuals showing behavioural imprinting on humans. (J29.8.w1)
  • Individuals which develop, during rehabilitation, severe Keel Lesions, Hock Lesions or Bumblefoot may require euthanasia. (J29.8.w1)
Species considerations:
  • If an individual is from an endangered or threatened species, or is an unusual species with small local population, or a species with a low reproductive potential, it may be considered inappropriate to euthanase despite the individual otherwise meeting the criteria for euthanasia. (D32.3.w3)
    • In the UK, it is particularly important to keep records showing the necessity for euthanasia of individuals of species which are specially protected under legislation such as the Wildlife and Countryside Act 1981 and The Wild Mammals (Protection) Act 1996. (B284.5.w5, W5.Jan01)
    • In the USA, approval by state or federal agents is required for euthanasia of individuals from threatened or endangered species. (D32.3.w3)
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Aims of Triage

The aims of triage are to concentrate available resources on those individuals which are most likely to survive and be returned to the wild and those which are endangered or threatened (B363.8.w8, P24.327.w4, P24.335.w12) and to prioritise which individuals will be treated first. (B335.11.w11)
  • In situations with large numbers of casualties, it may be necessary to concentrate available resources, including time of available personnel, on those individuals with the greatest chance of survival, rehabilitation and return to the breeding population, in order to ensure that the maximum number of healthy individuals can be released back into their environment. (B188, D135.5.w5, D159.III.w3, D183.w6, J4.181.w3, J29.8.w1, P24.335.w12)

Note: a triage strategy and triage criteria should preferably be developed as part of the oiled wildlife response plan and should be agreed by all stakeholders. (D183.w6, D183.w9)

  • Triage criteria should be documented and should be understood by all personnel involved in making decisions about individual casualty prioritisation. (B363.Intro.w21)
    • Pre-determined triage criteria for field triage may be set down as written instructions. (P14.7.w30)

Triage is not straightforward:

  • An individual which initially appears well may deteriorate rapidly; conversely one which appears unlikely to survive may improve rapidly following initial treatment. (P24.327.w4, P24.335.w12)
  • Birds will tend to hide their illness in the presence of a predator, including a human being. (P24.327.w4, P24.335.w12)
    • Severe injuries which may hinder recovery and return to the wild may not be detected initially. (P24.327.w4, P24.335.w12)
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Triage should be carried out by an experienced veterinarian, an experienced veterinary nurse or an experienced wildlife rehabilitator. (B363.8.w8, D159.III.w3, P24.327.w4, P24.335.w12)
  • The person carrying out triage must understand the reasons behind the necessity for triage and the limitations of resources, particularly time of trained personnel, available for treatment of casualties. 
  • If triage is carried out by inexperienced personnel there is a greater risk of those casualties in the worst condition being assisted first, to the detriment of those with the greatest chance of survival. (B363.8.w8, P24.327.w4)
  • Note: Triage should be carried out at the time of oiled casualty intake, but also throughout the rehabilitation process. (J29.8.w1)

Birds that are behaviourally alert, not emaciated and not seriously injured have the best chance of survival. (D214.2.w2)

Criteria which indicate a low chance of survival include: 

  • Persistent hypothermia (below 95F) despite attempts at warming; (D32.3.w3, D160.App5.w13) hypothermia below 38C or 100F. (B188)
    • Note: There are species differences in normal body temperature, which should be taken into account. Petrels and penguins, for example, may have lower normal body temperatures therefore 37C rather than 37.5C may be considered as the level below which euthanasia may be considered. (B363.App3.w16)
  • Hypothermia in combination with low weight for the species and lower than other birds of the same species and sex found in the same spill; (D32.3.w3, D160.App5.w13, J4.181.w3)
  • Low PCV (below 20%); (D32.3.w3, D160.App5.w13); haematocrit less than 15% (B188); particularly below 10% (P24.335.w12); below 10%. (J29.8.w1)
    • Birds with a persistently low PCV require prolonged rehabilitation and therefore are more likely to develop secondary diseases. (D32.3.w3, D160.App5.w13)
  • Low total proteins, (less than 1.0 g/dL). (P24.335.w12, J29.8.w1); less than 2.0 g/dL. (B188)
  • Signs of severe hydrocarbon toxicity. (B188)
  • Presence of severe wounds, fractures requiring surgery rather than just splinting, or illness. (B188)
  • During a large spill response, individuals developing open Keel Lesions, severe infection of the hocks (Hock Lesions) or severe bumblefoot may require euthanasia. (J29.8.w1)
  • Note: the degree of oiling is not relevant for triage. (B363.8.w8, D214.2.w2)

Identification of species is also important to ensure that species such as divers (loons), which are easily stressed, are treated promptly. (B188)

Three basic groups of birds in triage include:

  • 1) Endangered and threatened species, species protected by international agreements and individuals, of whatever species, which are oiled but otherwise appear healthy and thus have the best chance of survival. (B188, P24.327.w4, P24.335.w12)
    • Individuals of endangered species, or species of special concern, may be given priority over individuals of common species in the same clinical condition or in worse condition. (D160.5.w5)
    • Endangered species, species of special cultural significance, and species protected by international treaty are given priority. (B363.8.w8)
    • Birds with a near normal body temperature (39 to 40.5C), and with blood values within the normal range for the species, have the best chance of survival. (B363.8.w8)
    • Known breeding adults may also be given priority. (D183.w6)
  • 2) Individuals of common species and individuals which, due to the presence of complications such as hypothermia (body temperature below 39C), signs of toxicity or injury (e.g. fractures), or poor blood values, have less chance of survival. These birds should be treated when time is available after the first category birds have been treated. (B363.8.w8, P24.327.w4, P24.335.w12)
    • Basic methods to restore body temperature should be applied while these birds are awaiting treatment. (J29.8.w1)
    • These individuals should be left in a warm, quiet place while waiting for treatment. (B363.8.w8)
  • 3) Individuals which, due to severe hypothermia (less than 37.5C) and/or the presence of severe injuries such as compound fractures, are least likely to survive. These birds would be treated only if time allows after treatment of those in the first two categories. N.B. Moribund individuals and those with no chance of survival should be euthanased. (P24.327.w4, P24.335.w12)
    • Individuals with injuries such that they will not be releasable, due to permanent eye injury, permanent injury to, dysfunction or amputation of a limb, permanent feather abnormalities, or chronic infectious disease unresponsive to treatment, should be euthanased as soon as possible in order to prevent unnecessary suffering. (P24.335.w12)
    • Individuals with persistently low core body temperatures (less than 37.5C, less than 37C for petrels and penguins) despite repeated efforts to correct this. (B363.8.w8); core body temperature below 100F (J29.8.w1)
    • Individuals with serious injuries, infectious diseases, pronounced neurological signs, or poor risk of survival due to low body temperature (below 100F), very low total proteins, poor body condition or low haematocrit. (D159.III.w3)

Suggested categories for triage of sea otters:

A system suggested for Enhydra lutris - Sea otters, based on descriptions for triage of human war casualties, provides five categories: (B335.11.w11)

  • Urgent: In oiled otters, individuals requiring urgent intervention to prevent continued contamination or death; these animals require quick removal of oil by washing and immediate medical attention such as rewarming of hypothermic individuals, cooling of hyperthermic individuals, provision of fluids, etc. Examples are otters heavily oiled with fresh oil, and animals showing signs of hypothermia and hypoglycaemic shock. (B335.11.w11)
    • (For humans war casualties, individuals requiring urgent intervention to prevent death. (D163.12.w12))
  • Immediate: In oiled otters, these individuals need immediate washing plus treatment of minor medical problems; survival rates are high if these animals are treated quickly. Examples include those with moderate oiling, those heavily oiled with older (aged) oil, and individuals with moderate respiratory distress, mild hypothermia or hypothermia. It was noted that these individuals can tolerate short waiting periods for treatment (under supervision), in a thermoneutral environment (not causing panting or shivering) (B335.11.w11)
    • (For human war casualties, individuals presenting with severe, life-threatening wounds that require procedures of moderately short duration; these individuals have a high likelihood of survival. (D163.12.w12))
  • Delayed: In oiled otters, individuals moderately oiled with older (aged) oil, which are not showing clinical or behavioural signs of distress, as well as those with light or no oiling but with minor clinical signs such as periodic agitation or shivering; these individuals should be given food, water and rest and held for 12 to 24 hours, for treatment after those in the "urgent" and "immediate" categories. (B335.11.w11)
    • (For human war casualties, individuals for whom delay prior to operation will not unduly compromise the likelihood of a successful outcome; these individuals can be held until those in the urgent and immediate categories have been cared for. (D163.12.w12))
  • Minimal: In oiled otters, these individuals are those needing no cleaning or only minimal cleaning, and may only need a general physical examination. It is recommended that such animals be allowed 24 to 36 hours for stabilisation, under supervision and with food and water offered every three hours. These are otters with no or light oiling and not showing any clinical signs of distress. (B335.11.w11) 
    • (For human war casualties, individuals with only superficial wounds requiring cleaning, minimal debridement and simple (first-aid type) dressings (plus tetanus toxoid). (D163.12.w12))
  • Expectant: In oiled otters, these individuals show clinical and behavioural signs indicating little chance of survival, particularly those with severe subcutaneous emphysema (palpable), which is usually irreversible. These individuals should be made comfortable and observed for a short time.; euthanasia may be the most humane treatment for such animals. (B335.11.w11)
    • (For human war casualties, individuals with wounds which are so extensive that survival would be unlikely even if this was the sole casualty and optimum medical resources could be applied for their treatment. In a mass casualty situation such individuals should be made comfortable and given attendance by minimal but competent personnel. (D163.12.w12))
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Euthanasia Techniques

When euthanasia is required it should be carried out in a manner which will minimise associated stress and suffering.

The method chosen should be:

  • Appropriate for the size of animal;
  • Reliable;
  • Rapid in development of unconsciousness;
  • Designed to minimise stress;
  • Safe to the person carrying out the procedure, and to other observers;
  • Acceptable to the person carrying out the procedure;
  • Irreversible.

(D32.3.w3, D135.7.w7, D160.App5.w13, B36.5.w5 - Full text available)

Consideration should also be given, in choosing a euthanasia technique, to the emotional and aesthetic senses of other personnel involved in care of the oiled animals. (B363.App3.w16)

The preferred method of euthanasia is chemical euthanasia using an appropriate commercially available euthanasia solution such as a barbiturate solution. (B363.App3.w16, D32.3.w3, D135.7.w7, D135.7.w7, D159.III.w3, D160.App5.w13)

  • In birds, euthanasia solution should usually be injected into the medial metatarsal, right jugular or brachial vein. (D32.3.w3)
  • In mammals, euthanasia solution usually should be injected into the cephalic or saphenous vein or by intracardiac injection. (D32.3.w3)
  • Note: While intracardiac or intracoelomic injection can be used, these routes cause significant tissue damage, interfering with histopathological investigations. (B363.8.w8, P24.335.w12)
  • Intrahepatic injection may be used in individuals with impaired circulation. (B284.18.w18)
  • NOTE: legal restrictions on obtaining and using euthanasia solutions must be followed. (D32.3.w3, D135.7.w7, D160.App5.w13)

Alternative forms of chemical euthanasia include use of inhalation anaesthetics (to excess), or toxic gases. (D32.3.w3, D135.7.w7, D160.App5.w13)

NOTE: It is important to ensure that animals euthanased by injection of euthanasia solutions are disposed of safely so that they do not become food for animals which eat carrion. (D32.3.w3, D135.7.w7, D160.App5.w13)

  • Animals which are euthanased in the field must not be left in the field; they could be a source of secondary contamination or poisoning. (D160.5.w5)

Forms of physical euthanasia include dislocation of the cervical vertebrae, shooting, exsanguination and stunning. (D135.7.w7)

For further discussion of the ethics of euthanasia, descriptions of euthanasia methods and consideration of methods suitable for different species see: Wildlife Casualty Euthanasia (with special reference to UK Wildlife)

  • Information on euthanasia is also provided in the Field Manual of Wildlife Diseases Chapter 5 - Euthanasia (B36.5.w5 - Full text available)
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Records should be kept for each individual which is euthanased. These records should include, as a minimum:
  • Species;
  • Individual identification number;
  • Date and time of collection/admission;
  • Date and time of euthanasia;
  • Reasons for euthanasia;
  • Method of euthanasia, including drug name and volume used. (B375.1.w1)
    • N.B. Certain methods of euthanasia may affect findings at post mortem examination. (B363.8.w8, P24.335.w12)
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Post mortem Examination (Necropsy)

Following euthanasia, the carcass should be wetted down and refrigerated to await necropsy. (D32.3.w3, D135.7.w7)
  • If at all possible, the carcass should be kept refrigerated and necropsy should be carried out within 72 hours. 
    • If necropsy cannot take place within 72 hours then the carcass should be frozen. (D208.7.w7, D133.7.w7)
    • Freezing carcasses reduces the information which can be retrieved from them. If time does not permit full necropsy prior to freezing, efforts should be made, if at all possible, for samples of certain tissues (e.g. liver, kidney, lung, intestine) to be taken and stored in formalin before the rest of the carcass is frozen. (V.w5, V.w6)
  • Note: It is preferable for discussions regarding necropsy activities to be held with oil spill management authorities before a spill occurs, to ensure that there is approval for the activities and their associated costs. (D183.w6)

Reasons for necropsy

  • Necropsy findings from individuals which die or are euthanased may assist in the development of treatment protocols for live individuals during the spill. (D32.3.w3, D135.7.w7, D160.5.w5, D160.App5.w13, P24.335.w12)
  • Necropsy findings may assist in quantifying the physiological effects of specific types of oil (B23.38.w2, P24.335.w12), and of any treatments used. (B23.38.w2)
  • Necropsy findings assist in collection of data on both the effectiveness and limitations of rehabilitation. (D160.5.w5)
  • Necropsy findings may also be used as a way of measuring the frequency or prevalence of diseases in a given population or geographical area. (B23.38.w2, P24.335.w12)
  • Findings from necropsies may provide documented evidence if there is a legal enquiry following a spill. (P24.335.w12)
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Carcass Disposal

  • All carcasses (preferably following necropsy) must be disposed of properly. (D183.w6)
  • It is important to ensure that animals euthanased by injection of euthanasia solutions are disposed of safely so that they do not become food for animals which eat carrion. (D32.3.w3, D135.7.w7, D160.App5.w13)
  • Local regulations on the disposal of carcasses may vary. Disposal of highly oiled carcasses may require incineration. (D60.8.w8)
  • In the UK, the Environmental Health Department of the local authority should be consulted regarding Environmental Health regulations. (D27)
  • Note: Temporary storage, e.g. in excavated pits lined with plastic) may be required while appropriate disposal options are considered. (D60.8.w8)
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Authors & Referees

Authors Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Dr Virginia Pierce (V.w73)

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