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Introduction and General Information

Feeding of wildlife casualties should be based on their nutritional requirements, natural diet and feeding behaviour as far as possible. This includes consideration of the frequency of feeding.
  • Adequate nutrition of wildlife casualties and convalescents relies on an understanding of their requirements and a knowledge of their natural diet.
  • A diet which meets the nutrient requirements but in a form unfamiliar to the casualty may not be recognised as food and may not be eaten by the animal.
  • There may be significant differences in preferred diets between even closely related species.
  • Food should be of high quality.
  • Ingestion of food should be monitored, not assumed. This may include weighing food before presentation and weighing waste food after removal, and periodic weighing of the animal.
  • Monitoring of weight/body condition is particularly important for group housed/group fed animals, within which some individuals may take more food and others not get the food they require.
  • Feeding of convalescents should take into account their requirement for additional nutrients for healing as well as maintenance requirements.
  • Nutritional deficiencies increase susceptibility to infectious disease.
  • FRESH CLEAN WATER should always be available, even for species which rarely drink.

Calculation of food requirements:

Basal Energy Requirement (BER):

  • The Basal Energy Requirement (BER) varies depending on the taxonomic group concerned.
  • The BER can be calculated in terms of Kcal per day for different taxonomic groups using the following calculations:
  • Mammals (eutherian): 70 x (weight in kilograms).75
  • Mammals (marsupial): 49 x (weight in kilograms).75
  • Birds (passerine): 129 x (weight in kilograms).75
  • Birds (non-passerine): 78 x (weight in kilograms).75
  • Reptiles: 10 x (weight in kilograms).75
  • (B192)
  • In most circumstances the amount of energy required per day is greater than the basal energy requirement. Equations are available which indicate the energy requirement for animals in different circumstances:
    • Growth: 1.5-2.0 x BER
    • Enclosure rest: 1.25 x BER
    • Following starvation: 1.25 x BER
    • Post-surgery: 1.25 x BER
    • Severe burns: 1.5 - 2.0 x BER
    • Sepsis: 1.5-2.0 x BER
    • Trauma: 1.5 x BER
    • Neoplasia (cancer) 1.5 x BER
    • Hepatic (liver) disease: 1.25 x BER
    • Severe renal (kidney) disease: 1.25 x BER
    • (B192)

(B203, J2.24.w2, P19.1.w30, D28, V.w5, V.w26)

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Water / Fluids / Hydration

  • Drinking water should be made available at all times unless the clinical condition of the casualty (inability to lift/control the head or inability to swallow) means that this would endanger the animal, or with species that do not drink water from bowls, such as swifts (Apus apus - Common swift).
  • The amount of water and the container in which it is provided should be appropriate for the species.
    • bowls of various sizes and materials are appropriate for many species. The animal should not be able to tip the bowl over.
    • small mammal drinker bottles sold for pet mice, hamsters etc. may also be useful for small rodents.
  • If the casualty is unable to drink naturally then fluids must be provided by alternative means, for example:
    • from a dropper or syringe
    • on a paint-brush
    • stomach tubing (gavage)
    • parenterally (by subcutaneous, intravenous, intraosseous or peritoneal injection, as appropriate).
  • Appropriate rehydration (electrolyte) solutions should be made available on admission to casualties which are or may be dehydrated; in practice this may be assumed for all casualties.
    • A basic oral rehydration (electrolyte) solution may be made by dissolving one tablespoon of sugar and one teaspoon of salt in one litre of water.(B203)
    • Some individuals will drink rehydration (electrolyte) solutions but will not drink water, for others the reverse is true. Both should be made available initially.
    • The use of fruit-flavoured rehydration solutions designed for humans may encourage drinking, particularly in animals for which fruit is a part of their natural diet.
  • The required fluid intake for maintenance should be considered when designing convalescent diets.
  • (B203, V.w5, V.w26)


  •  It is generally reasonable to assume 10% dehydration for casualty wild mammals and birds. (B197.15.w15)
  • Continue giving supplementary fluids while there is clinical evidence of dehydration, even if the bird is self-feeding.(B197.15.w15)
  • Oiled birds may require supplementary fluids for 4-8 days even if they are self feeding. (B197.15.w15)

More information on specific subject areas is available at the bottom of this page in:

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Convalescent diets

Little published information is available on convalescent diets suitable for non-domestic animal species.
  • Energy requirements for maintenance and healing should be calculated and used to determine the quantity of food required (see Basal Metabolic Rate calculations above).
  • Diet should be easily absorbed/digested.
  • Care should be taken not to under or over supplement with vitamins/minerals.
  • Diets intended for feeding from a syringe or by stomach tube (gavage) must be of a sufficiently fluid consistency to pass through the syringe nozzle and down the tube without it becoming blocked.
  • The natural diet should be considered when deciding on suitable ingredients, including consideration of taste/smell.
  • Proprietary products suitable for convalescent cats/dogs may be useful for carnivorous species and insectivorous mammals.
  • Proprietary products intended for convalescent humans, or for babies, may be more suitable for species with a grain or fruit-based diet.
  • The required fluid intake for maintenance should be considered when designing convalescent diets.
  • Water should be freely available and provided in a manner appropriate for the species such as to avoid the risk of drowning.

More information on specific subject areas is available at the bottom of this page in:

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Short-term Maintenance diets

When considering the feeding of wildlife casualties several factors need to be considered.

1) Food is of no nutritional value if it is not eaten. This statement may appear redundant, nevertheless it is of vital importance.

  • With small, high-metabolic rate species in particular, it is vital that the animal feeds within a short time, as reserves are minimal and sufficient for a short period only.
  • Specialist feeders (in terms of both natural diet and normal diet acquisition) and nervous species are least likely to eat food provided in captivity.
  • Offering food which is similar in appearance to the natural diet may be of great importance in persuading animals to eat in captivity.

    (J23.16.w4, J23.23.w1)

2) The requirements for maintenance and healing of the animal must be provided.

  • Guidelines may be available for quantities of food to be fed to a particular species per day (e.g. number of day old chicks per day for a species of raptor).
  • Formulae have been developed for the calculation of energy requirements based on body mass (see Basal Metabolic Rate calculations above).
  • Requirements for healing of injuries, regaining weight lost prior to capture and other factors such as pregnancy must be taken into account.
  • The nutrient value of foods given must be considered, in terms of energetics and other requirements.
  • For example it has been calculated that mealworms Tenebrio average 204kcal/100g, blowfly larvae (Calliphoridae) 150kcal/100g and shin beef 177kcal/100g. The quantities of these foods required to meet the energetic requirements of e.g. an insectivorous mammal or bird would be larger than those of prepared "insect" mixtures with a higher caloric content.(J23.16.w4)
  • Captive-raised mealworms and blowfly larvae tend to be low in calcium, phosphorus and vitamins D3, A, E and B-complex, lower in protein, fats and particularly carbohydrate than might be expected and may contain a fairly high quantity of relatively indigestible chitin (J23.16.w4).
  • Mineral and vitamin supplementation of diets may be required but care must be taken to not only to avoid under-supplementation but also not to over supplement or to make diets unbalanced by the use of supplements.

3) The advisability or otherwise of feeding to produce a relatively fat animal for release.

  • In some cases it may be advantageous for an animal to gain weight in captivity to a point over that which would be expected in the wild. This additional weight could then be expected to act as a "buffer" which would provide the animal with energy while it is learning to acquire food in the wild (for example juveniles after hand rearing).
  • However for species which rely on speed to acquire food (e.g. many birds of prey) feeding to excess in captivity and therefore releasing at too high a body weight may be severely detrimental to the ability of that individual to catch prey.

More information on specific subject areas is available at the bottom of this page in:

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Human Health Consideration

Food intended for animal use should be prepared and stored separately from food intended for human use.(V.w5)

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Detailed Individual / Species-specific Techniques

Associated techniques linked from Wildpro MAMMALS




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UK Contact Organisations and Published Guidelines for Further Reading (Electronic Library)

(UK Contacts)

(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

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Authors & Referees

Author Debra Bourne
Referees Becki Lawson and Suzanne Boardman

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