ENRICHMENT: Ethological evaluation of minimal requirements for the housing of mice as lab animals and pets

The mouse is the most widely used laboratory animal, yet surprisingly little is known about its behavioural needs. Legal minimal requirements for the housing of mice are based on an arbitrary quantity of space per mouse, which in Switzerland differs 5-15-fold depending on whether a mouse is kept as a pet or a laboratory mouse. We have recently shown that space per se has little impact on the welfare of mice, but that more space may be needed to implement effective enrichment. Here we propose to assess enrichment options in terms of: (i) their use and demand by the animals, (ii) their impact on animal welfare, and (iii) the space needed for their implementation. Our results will provide a better evidence-based for the specification and implementation of minimal housing requirements for mice, based on the quality of space rather than an arbitrary quantity of space. This will likely benefit the welfare of laboratory mice, but should also promote the acceptance of the legal minimum requirements by both researchers and the public.