From house mouse to mouse house:: the behavioural biology of free-living Mus musculus and its implications in the laboratory

Understanding a species' behaviour in natural conditions can give insights into its development, responses and welfare in captivity. Here, we review research and pest control literatures on the free-living house mouse (Mus musculus), analysing its sensory world, developmental processes and behaviour to suggest how laboratory environments might affect mouse welfare, normalcy, test design, and behaviour. Mouse development from foetus to weaning is influenced by prenatal stress and nutrient levels, and post-natal litter size and other factors affecting maternal care, all with lasting effects on adult bodyweight, aggression, activity levels, stress responsiveness and masculinisation. These influences may well be important in the laboratory, for example unwittingly differing between facilities leading to site-differences in phenotype. Murine senses are dominated by olfactory, auditory and tactile cues. Their hearing extends into the ultrasonic, and vision, from mid-range wavelengths to the ultraviolet. In mouse facilities, behaviour and welfare may therefore also be affected by sensory stimuli unnoticed by humans. The physical and social environment and behaviour of wild mice differ greatly from those of laboratory mice. Dispersal age varies with resource-levels and social cues, and mice often either live alone or in family groups. Mice occupy territories/ranges measuring a few square meters to several square kilometers, and which allow running, climbing, and buff owing. Mice are often active during dawn/dusk, and spend their time patrolling their territories, investigating neighbours' odour cues, foraging, finding mates and rearing litters. The potential impact of these many differences and restrictions on laboratory mouse development, normalcy and welfare has only begun to be explored. (C) 2004 Elsevier B.V. All rights reserved.