How does habitat structure affect activity and use of space among house mice?

For small mammals that are vulnerable to predation, the protection provided by physical structuring within the habitat is important in determining suitable nest or resting sites but little is known about how different aspects of structure affect use of the habitat more generally. We examined the effects of ground-level structure (open/complex), overhead cover (present/absent) and the distribution of protected nest sites and food (clumped together/scattered) on activity and use of space among house mice, Mus domesticus, in enclosures. Adult pairs were housed in eight habitat types differing in arrangement of nestboxes, bricks and cover sheets, and their location was monitored under infrared light every 0.5 s over 4 h during the dark period. The mice spent much more time within protected nest sites and were more restricted in use of different sites within habitats that had little ground-level structure and no overhead cover. Much wider use was made of structurally complex habitats. Complex ground-level structure had the greatest impact on emergence from protected nest sites and use of space, since mice preferred to stay close to, or on top of, walls and other objects when undisturbed. The influence of overhead cover on normal activity depended on the extent of ground-level structure and origin of the mice, but, when disturbed by an experimenter, mice sheltered under overhead cover or in enclosed nest sites. Preference between nest sites depended on accessibility from under overhead cover and proximity to enclosure walls. We found almost no sex differences in activity or use of space. (C) 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.