Rodents

Here we provide general information on the housing and husbandry requirements of commonly used laboratory rodents, including mice, rats, guinea pigs, gerbils and hamsters. More detailed guidance can be found in the resources and references provided.

 

Basic requirements

Basic requirements for good rodent housing and husbandry are given in the table below.

Housing in stable, compatible groups - it is important to take into account sex, age, reproductive condition, familiarity, prior group housing experience when grouping the animals.
Enclosures designed to cause minimum disturbance to the animals.
Enough space for exercise, normal social behaviour (e.g. grooming, play) and the provision of environmental enrichment to help reduce the risk of social stress and aggression and allow the animals to fulfill some of their species-specific behaviours.
Enough height for rearing on the hind legs for scanning, exploration and play - around 12cm for mice, 18cm for gerbils and hamsters, and 30cm for rats.
Solid floors with an adequate depth of an appropriate substrate (e.g. 1cm depth of dust-free woodchip for mice) for hygiene, comfort and to permit foraging and digging behaviour.
Material to gnaw (e.g. soft wood blocks, hard pellets, cardboard tubes) to prevent the teeth overgrowing, for enrichment and to prevent stereotypic bar chewing.
Refuges (e.g. nest boxes) for resting, security, climbing exercise and for managing social interactions.
Vertical barriers or tubes (e.g. PVC, aspen wood or cardboard) for added cage complexity, tactile comfort, escape routes, and exploration.
Nesting material (e.g. soft paper or soft wood) for comfort, to help regulate temperature and light levels, and to hide and retreat from cage mates or threatening stimuli. Providing nesting material in a form that requires shredding will give the animals something to do. Nesting material is essential for parturient females. Nest boxes should be provided if insufficient nesting material is provided for the animals to build a complete, covered nest.
Appropriate lighting levels and regimes. Low light levels and racks with shaded tops and /or refuges and nesting material, where they can hide from too much light, will help reduce the risk of retinal degeneration, especially for albino animals
A varied diet and the ability to forage - scattering food (e.g. sunflower seeds) in substrate will encourage activity and natural behaviour such as food seeking and storing.
Minimisation of extraneous noise and ultrasound.
Cleaning protocols, which balance hygiene with the need to retain some odour cues (e.g. scent-marked nesting material) to avoid stress and aggression.
Gentle and frequent handling from early in life – see Handling and Restraint 
Running wheels, activity disks and frames, ropes, string and chains for climbing may also be beneficial for rodents.
Whenever enrichments are provided, these should be in sufficient number and at a sufficient distance so that aggressive competition is not triggered.

Mice

The laboratory mouse is derived from the wild house mouse (Mus musculus), a largely nocturnal burrowing and climbing animal which builds nests for regulation of the microenvironment, shelter and reproduction. Mice do not readily cross open spaces, preferring to remain close to walls or other structures. A wide range of social organisations has been observed depending on population density, and intense territoriality may be seen in reproductively active males. Pregnant and lactating females may aggressivley defend their nests. Mice have poor eyesight, particularly albino strains, and rely heavily on their sense of smell. They scent marking their environment within urine. Mice also have very acute hearing and are sensitive to ultrasound. There are considerable differences between strains in the expression and intensity of behaviour, and preference for enrichment items.

Individually ventilated cages

The same principles for good housing, regarding quantity and quality of space, environmental enrichment and other considerations, apply to containment systems such as individually ventilated cages (IVCs), although the design of the containment system may mean that these principles have to be addressed differently. The draught induced by high intra cage-ventilation rates in some IVCs can induce chronic stress and heat loss. The location of the air supply to the cage (e.g. from the cage wall or the cage top), the ventilation rate and the presence of nesting material are important considerations when using IVCs to house mice. Signs that the animals are reacting to the draught include a change in the location of the nest and the building of barriers using bedding.

Rats

The laboratory rat is derived from the wild brown rat (Rattus norvegicus) and is a highly social animal. Rats avoid open spaces, and use urine to mark their territory. Their sense of smell and hearing are highly developed, and rats are particularly sensitive to ultrasound. Daylight vision is poor, but dim-light vision is effective in some pigmented strains. Albino rats avoid areas with light levels over 25 lux. Activity is greater during hours of darkness. Young animals are very exploratory and often engage in social play.

Laboratory rats released into the wild from NC3Rs on Vimeo.

Video of the responses of laboratory-raised rats on release into the wild. Despite many generations of breeding in captivity, these animals retain the capacity to perform many behaviours that the laboratory environment can prevent. For more video clips from the film 'The Laboratory Rat: A Natural History' visit www.ratlife.org

Guinea pigs

Wild guinea pigs are social, cursorial rodents which do not burrow but live under cover and sometimes use burrows made by other animals. Adult males may be aggressive to each other but generally aggression is rare. Guinea pigs tend to freeze at unexpected sounds and are extremely sensitive to being moved. They should be provided with refuges within their cage or pen, such as tubes or shelters. Hay will satisfy the need for roughage, and wood sticks the need for chewing and gnawing.

Gerbils

The gerbil or Mongolian jird (Meriones sp.) is a social animal and is largely nocturnal, although in the laboratory it is also active during daylight. Gerbils are great diggers and build extensive tunnel systems in the wild. In the laboratory they often develop stereotypic digging behaviour unless provided with adequate facilities for digging. For this reason gerbils need comparatively more space than other rodents in order to allow them to build and use burrows of sufficient size. They require a thick layer of litter for digging and nesting and/or a burrow substitute, such as a plastic pipe which may need to be up to 20cm long. Nesting material (e.g. hay, straw, etc.) and wood sticks can be used for chewing and gnawing.

Hamsters

Hamsters are burrow digging, nest building rodents. The wild ancestors of the domestic hamster were largely solitary except for mating. Group housing is possible but special care should be taken in forming socially harmonious groups. Compatible groups of animals will sleep and huddle together. Environmental enrichment should include nesting material, a refuge area (e.g. tube, plastic shelter), roughage and gnawing objects. Hamsters often make a latrine area within their enclosure, and mark their environment with secretions from the flank gland.

Related resources

Refinement of Housing and Handling Conditions and Environmental Enrichment for Animals Kept in Laboratories Animal Welfare Institute Database
Rodent Welfare Group meetings RSPCA/UFAW 
Laboratory Animal Refinement and Enrichment Forum (LAREF) Animal Welfare Institute. For exchange of information and experiences on ways to improve laboratory animal housing and care
www.mousebehavior.org Stanford University. A wiki ethogram for the laboratory mouse
Validating refinements to laboratory housing: asking the animals. NC3Rs invited article. Sherwin C (2007) 
View PDF
Refinement of rodent research through environmental enrichment and systematic randomization. NC3Rs invited article. Würbel W, Garner JP (2007) 
View PDF
Making sense of scents: reducing aggression and uncontrolled variation in laboratory mice. NC3Rs invited article. Hurst J (2005) 
View PDF

References

  • Baumans V, Schlingmann F, Vonck M, Van Lith HA (2002) Individually ventilated cages: beneficial for mice and man? Contemporary Topics 41: 13-19.
  • Baumans V (2005) Environmental enrichment for laboratory rodents and rabbits: requirements of rodents, rabbits and research. In: Enrichment Strategies for Laboratory Animals. ILAR Journal 46: 162-170.
  • Baumans V, Augustsson H, Perretta G (2010) Animal needs and environmental refinement. In: The COST Manual of Laboratory Animal Care and Use, Refinement, Reduction and Research (Eds. Howard B, Nevalainen T, Perretta G). CRC Press, London.
  • Baumans V, Van Loo PLP, Pham TM (2010) Standardisation of environmental enrichment for laboratory mice and rats: utilisation, practicality and variation in experimental results. Scandinavian Journal of Laboratory Animal Science 37: 1-14.
  • Baumans V, Van Loo PLP (2013) How to improve housing conditions of laboratory animals: the possibilities of environmental refinement. The Veterinary Journal 195: 24-32.
  • Burn CC (2008) What is it like to be a rat? Rat sensory perception and its implications for experimental design and rat welfare. Applied Animal Behaviour Science 112: 1-32.
  • Gaskill BN, Gordon CJ, Pajor EA et al. (2012) Heat or insulation: Behavioral titration of mouse preference for warmth or access to a nest. PLoS ONE 7(3): e32799.
  • Harris A, D'Eath RB, Healy SD et al. (2009) Environmental enrichment enhances spatial cognition in rats by reducing thigmotaxis (wall hugging) during testing. Animal Behaviour 77: 1459-1464.
  • Hubrecht RC, Kirkwood J, Eds. (2010) The UFAW Handbook on the Care and Management of Laboratory and Other Research Animals, 8th Edition, Wiley-Blackwell.
  • Jennings M, Batchelor GR, Brain PF et al. (1998) Refining rodent husbandry: the mouse: Report of the Rodent Refinement Working Party. Laboratory Animals 32: 233-259
  • Nicol CJ, Brocklebank S, Mendel M et al. (2008) A targeted approach to developing environmental enrichment for two strains of laboratory mice. Applied Animal Behaviour Science 110: 341-353.
  • Reinhardt V, Reinhardt A, Eds. (2002) Comfortable Quarters for Laboratory Animals, 9th Edition, Animal Welfare Institute.
Information provided by Vera Baumans, University of Utrecht
Last updated: June 2013