TECHNIQUE

Hand-rearing Mice & Voles (Wildlife Casualty Management)

Summary Information
Type of technique Health & Management / UK Wildlife Casualty Management / Techniques:
Synonyms and Keywords N.B. This information should be read in association with Hand-rearing of Orphaned Wildlife which contains background information together with links to the Electronic Library and Organisations (UK Contacts). The related Species pages contain similar linkages.
Description This page has been prepared for the "UK Wildlife: First Aid and Care" Wildpro module, and is designed for the needs of the following species: Apodemus flavicollis - Yellow-necked mouse, Apodemus sylvaticus - Wood mouse, Micromys minutus - Harvest mouse, Mus musculus - House mouse,  Arvicola terrestris - European water vole, Clethrionomys glareolus - Bank vole, Microtus agrestis - Field vole, Microtus arvalis - Common vole.

These species are within the family Muridae.

Initial Care: 

General mammal information: 

  • On arrival any young mammal should be weighed, warmed, stimulated to urinate/defecate and given supplementary fluids by an appropriate route to counteract dehydration.
  • The age should be determined if possible. (See individual species information pages, sections "Appearance - Neonate" and "Life Stages - Reproductive stages").
  • The first feed given should be an oral rehydration (electrolyte) solution (e.g. Lectade, Pfizer Limited), with a gradual changeover to a milk substitute over several feeds.
  • See: Hand-rearing of Orphaned Wildlife for further general information. for further general information.

General Care (including warmth and hygiene):

General mammal information

  • Young mammals have poor ability to maintain body temperature and are prone to hypothermia, hyperthermia and burns, particularly when unfurred or sparsely furred.
  • Keep out of draughts but ensure ventilation is adequate.
  • Provide a temperature range, e.g. by heating one end of the container more than the other, which, while not allowing either overheating or chilling, permits the animal to chose the position at which it feels most comfortable.
  • The container used should be sufficiently large to allow the occupant to move into a comfortable position.
  • The sides of the container should be sufficiently high to prevent the occupant falling out.
  • Bedding materials should be soft, comfortable and either disposable or easily washed. They should keep the animal dry and be changed as frequently as necessary to prevent soiling.
  • (B194, P3.1987.w5, V.w5)

Small mammal information:

  • Maintain small mammals initially at 32C, then 28C, later 23C.(P3.1987.w5)
  • Initially at 95F for a hairless baby, 90F for a haired infant with the eyes still closed, and reduce by 5F per week once the eyes are open.(B194)

Milk replacer:

Suggested milk replacers include:

  • Mice:
  • Esbilac (Pet Ag) 75%, colostrum 25%.(B151)
  • Small amount calcium-phosphorus supplement (Stress, Philips Yeast Products) added once daily (dip feeding brush).(B151)
  • Voles:
  • Esbilac (Pet Ag) 75%, colostrum 25%.(B151)
  • Small amount calcium-phosphorus supplement (Stress) added once daily (dip feeding brush) (B151)
  • Esbilac (Pet Ag). (B156.12.w12)

Utensils:

  • Small artist's paintbrush or small pastette (plastic Pasteur pipette) with small Catac teat attached.(B151)
  • A piece of string wicking milk from the bottle for very small orphans, later a teat may be used.(B195)
  • A medicine dropper may be used.(B194)
  • Small syringe (1ml) with a fine blunt-ended catheter tip attached, cut down to about 0.5cm long.(V.w27)

Feeding Frequency:

General mammal information: 

  • Varies depending on species.
  • In general, every 2-3 hours during the day and longer intervals at night.(P3.1987.w5)
  • More frequent feeding (e.g. every hour) may be required for very small species, particularly for neonates.(V.w5)

Mouse and vole specific information:

  • Every hour from early morning to late at night, every two hours during night.(B151)
  • Every hour 6am to midnight and every two hours during the night for pinkies (unfurred infants) only; night feeds are not required for furred young.(V.w27)

Feeding Technique: 

Small mammal information:

  • To encourage feeding in very small animals, place a drop of milk on lips, preferably with animal held upright.(P3.1987.w5)
  • To feed using a medicine dropper:
    • Hold the infant in one hand with its head slightly higher than its body, place the dropper just inside the animal's lips and press the bulb extremely gently to place a tiny drop of formula in the infant's mouth to encourage feeding to start. As it begins to suck or lick the dropper may be pressed very gently to assist the infant to take the formula.(B194)
    • If a bubble of liquid appears at the nose or the infant opens its mouth wide, immediately stop feeding and tilt the infant head down to allow the excess formula to drain from its mouth. Give the infant a chance to recover then start again more slowly.(B194)
    • Refill the dropper as required.(B194)
    • Some infants may feed by licking individual hanging drops of the end of the dropper.(B194)
    • Clean any excess from the infant's nose/chin after each feed (B194).
  • A similar technique can be used with a small syringe, pressing very slowly on the plunger as the infant sucks or licks.(V.w5)
  • When feeding very small neonates it is vital that the feeding technique used provides milk at a sufficiently slow rate to minimise the risk of milk being inhaled with resultant aspiration pneumonia. (V.w26)

Mouse and vole specific information:

  • A piece of string may be used as a 'wick' which the orphan can suck on initially, later allow to suck on a teat.(B195)
  • Using a fine blunt-ended catheter attached to a small syringe, place droplets into the infant's mouth very slowly. (V.w27)

Quantities:

General mammal information:

  • Energy intake (kilocalories per day) = 200-250 x bodyweight (kg) 0.83. (P19.1.w5, P3.1987.w3)

General rodent information:

  • May be fed up to 35-40% of body weight per day, and about 25-50ml/kg per feed. (J34.9.w1)

Mouse and vole specific information: 

Toileting:

General mammal information:

  • Most infant mammals require gentle stimulation of the ano-genital area (using e.g. a damp cotton bud, damp cotton wool or damp soft paper towel) in order to urinate and defecate. 
  • This should be done when the animal is first presented and at every feed until voluntary elimination is observed.

Weighing: 

General mammal information:

  • Weigh daily. 

Weaning:

  • Mice:
    • Start offering food items at about nine days old (eyes still closed), initially crumbled digestive biscuits or rusks scattered on floor.(B151)
    • Offer cereal soaked in milk formula, then crackers, small pieces of apple and vegetables.(B195)
    • Move into a cage once active.(B195)
    • First add baby cereal and/or baby food to the milk. For the first dry food, offer dry breakfast cereals (e.g. oat or wheat based) and nuts initially. Once the infant is eating well add fruits and other foods, e.g. grape, orange, apple, green lettuce, wholemeal bread, carrot and wild seeds. Ensure the infant eats a good range of foods.(B194)
  • Voles:
    • From about nine days old (eyes still shut), offer green food such as chickweed, dandelion, and clover.(B151)

Release:

Appropriate Use (?)
  • Wild animals should not be taken for hand-rearing unless they are definitely orphaned, abandoned or injured, or in immediate danger.
Notes
  • An ordinary outdoor thermometer may be used to indicate the temperature in the container used to house the orphan. (B194)
  • Routine records should be maintained of daily weight, times of each feed, quantities of milk consumed, urine/faeces production and general condition/demeanour. Such records provide an objective means of assessing progress and provide useful data for improving rearing methods.(V.w5)
  • Practice with fine control of a syringe is required to enable milk to be given a drop at a time.(V.w5)
Complications/ Limitations / Risk
  • Rearing of very young, hairless orphans is difficult.(B195)
  • Care not to overfeed, since only very small quantities are required.(B195)
  • Re-sterilised syringes should be discarded when the plunger begins to stick as the additional pressure required to move the plunger may result in excessive quantities of fluid being accidentally deposited in the infant's mouth.(V.w5)
Equipment / Chemicals required and Suppliers
  • Esbilac (Pet Ag, Kruus UK Ltd., Unit 17, Moor Lane Industrial Estate, Sherburn in Elmet, North Yorkshire, LS25 6ES, UK): from pet stores.
  • Stress (Philips Yeast Products, Park Royal, London, England): from pet stores.
  • Colostrum: local farms.
  • Lectade, Pfizer Limited: from veterinary suppliers.
Expertise level / Ease of Use
  • Initial time commitment for infants requiring frequent (e.g. hourly) feeding is extreme and would be prohibitive for most people.
  • Manual dexterity is important for caring for these very small individuals. 
  • Requires empathy, observation skills and the ability to "read" the animal's body language.
  • Experience with hand-rearing is useful and likely to greatly increase the success rate.
Cost/ Availability
  • Products and equipment all widely available, not particularly expensive.
Legal and Ethical Considerations
  • Hand-rearing should not be started unless the carer is prepared to give the time and effort required for rearing to release, or to ensure that appropriate care will be continued through to release.
  • Consider whether hand-rearing is the best option for the individual compared with leaving it in the wild.
  • Consider whether euthanasia is a more humane/kinder option for the individual than attempting hand-rearing.
  • An offence may be committed under the Abandonment of Animals Act, 1960 Section 1 if a released animal does not have a reasonable chance of survival (i.e. a chance similar to its non-rehabilitated peers). It is an offence under this Act for a person having control or charge of an animal to abandon it permanently or otherwise in circumstances likely to cause unnecessary suffering. This may include release at an unsuitable site, in the wrong territory, unfit, not having learned to hunt, at the wrong time of year etc. (J35.147.w1, B156.21.w21, B223, W5.Jan01)
  • See: Legislation relating to Wildlife Casualties
Author Debra Bourne
Referee Becki Lawson and Suzanne Boardman
References

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