TECHNIQUE

Catching and Handling of 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 Wildlife Casualty Handling and Transport 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.

Catching:

  • Catching by hand may be possible, although these species are agile and may move very fast.
    • A small net (size suitable for catching small birds) may be useful for catching.
    • Fine mesh size minimises the risk of entanglement in a net, particularly of claws.
  • Grasp head and neck firmly through the net before carefully working the net off the animal.
  • May be transferred directly from a net into a suitable container without direct handling if examination is not required.
  • Within a confined space, the animal may be guided into a corner, a hand may be cupped over it and the middle or base of the tail is then grasped with the other hand.(B169.17.w17)
  • It may be possible to place a jam-jar over the animal then slide a piece of thin card along the ground to trap the animal before lifting the jar.
  • Small rodents may be suspended by the tail (mid/base) for a few seconds only, e.g. while being transferred between containers.(B156.9.w9, B169.17.w17)
    • Do not hold by the tip of the tail as the skin may slough off. (B169.17.w17)
  • Transfer into a small container as soon as possible after capture and for transport.
  • Transfer between cages may be achieved most easily by allowing the rodent to run into a cardboard or plastic tube, covering the ends of the tube, then transferring the tube into the new container.

Handling:

  • May be held initially by the base of the tail then the head pinned between thumb and forefinger to avoid biting.
  • Small rodents can generally be held and picked up by gripping the scruff of the neck between the thumb and first finger of one hand.
  • May be held briefly with a hand grasping firmly but gently around the whole body.(B151)

Restraint for examination and treatment:

  • Brief examination and minor treatment may be carried out using physical restraint.
  • Alternatively, and if lack of movement is important, the use of chemical restraint may be advisable.
  • Once the scruff is held firmly the animal may be held upside down with the body resting on the palm of the hand while the grip on the scruff is maintained.
  • For mice, the tail may then be gripped using the third and fourth fingers.

(B16.2.w2, B123, B151, B156.9.w9, B169.17.w17, B169.20.w20, B187.26.w26)

General Anaesthesia and Sedation:

 Suggested protocols for sedation and general anaesthesia include:

  • As with other small mammals general anaesthesia may be induced in an anaesthetic chamber.
  • Mask induction of general anaesthesia may also be used, but this can lead to handling stress.
  • Isoflurane is the anaesthetic agent of choice.
  • Halothane may be used as an alternative to isoflurane.
  • Maintain on isoflurane inhalation anaesthesia with oxygen (no nitrous oxide), delivered via a face mask e.g. made from a plastic syringe barrel.
  • Use a low-resistance circuit such as a T-piece.
  • Allowing some leakage from the face mask further reduces resistance;
    • Some form of active scavenging should be used to reduce atmospheric pollution.
  • Avoid excessively high flow rates of oxygen, as this increases heat loss and the risk of hypothermia.
  • Consider fluid therapy during general anaesthesia of small mammals to replace water losses; subcutaneous fluids would be appropriate.
  • Action should be taken to reduce heat loss of small mammals during general anaesthesia, to reduce the risk of hypothermia e.g. keep on a heated pad during general anaesthesia and recovery.
  • (J15.20.w2, B205)
  • Starvation prior to general anaesthesia should not be performed in these small species.
Appropriate Use (?)
  • Catch only if necessary.
  • Handling of wild animals should be minimised.
  • Consider design of accommodation and timing of treatments to minimise requirements for capture and handling.
  • Consider whether physical or chemical restraint is more appropriate.
  • Reduce handling as much as possible as this will stress wild rodents.
Notes
  • Wild rodents are less tractable than pet rodents and are more likely to bite.
  • Harvest mice rarely bite.
  • Rodents often struggle violently when restrained.(B123)
  • Gloves give some protection from bites and may increase the confidence of the handler.(B151)
  • Thin gloves such as domestic rubber gloves may provide the best compromise between protection from bites and reduced dexterity.(B169.17.w17)
  • Fine mesh size minimises the risk of entanglement in a net, particularly of claws.(B123)
Complications/ Limitations / Risk
  • Risk of damaging the animal by trapping with the rim of a net, or by holding too tightly.
  • Handling wild mice always involves a risk of bites. (B169.17.w17)
  • Gloves thick enough to give full protection against bites are likely to reduce sensitivity, dexterity and control; this may lead to injury to the animal and increase the risk of escape.
  • Do not hold by the tip of the tail as the skin may slough off. (B169.17.w17)
  • Risk of entanglement of e.g. claws in the net (fine mesh size minimises the risk of such entanglement).(B123)
  • Considerable risk of hypothermia when small mammals are anaesthetised.(B123, B205)
Equipment / Chemicals required and Suppliers
  • Nets may be obtained from specialist suppliers, veterinary suppliers or good pet stores; their cost is variable.
  • Gloves and glass jars are widely available.
  • Nets may be hand-constructed from readily-available inexpensive materials.
  • Some drugs used for chemical restraint are expensive.
  • Drugs used for chemical restraint may only be available to veterinary surgeons or other licensed persons.
Expertise level / Ease of Use
  • Good manual dexterity is useful.
  • Easier with experience.
  • N.B. wild rodents are more difficult to handle than tame pet or laboratory rodents.(B123)
Cost/ Availability
  • Nets may be obtained from specialist suppliers, veterinary suppliers or good pet stores; their cost is variable.
  • Gloves and glass jars are widely available.
  • Nets may be hand-constructed from readily-available inexpensive materials.
  • Some drugs used for chemical restraint are expensive.
  • Drugs used for chemical restraint may only be available to veterinary surgeons or other licensed persons.
Legal and Ethical Considerations
Author Debra Bourne
Referee Becki Lawson and Suzanne Boardman
References J15.20.w2, B16.2.w2, B123, B151, B156.9.w9, B169.17.w17, B169.20.w20, B187.26.w26, B205

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