Illumination and the perception of remote habitat patches by white-footed mice

Perceptual range, or the distance at which habitat 'patches' can be perceiv ed, constrains an animal's informational window on a given landscape. If su ch constraints are great, they may limit successful dispersal between dista nt habitat patches. On dark nights, nocturnal white-footed mice, Peromyscus leucopus, have surprisingly limited perceptual abilities regarding distant forested habitat. In fact, their ability to orient towards such habitat wh ile travelling in a bare agricultural field indicates a perceptual range un der 30 m. However, increasing illumination can increase perceptual range. F or example, full moonlight extends the perceptual range of mice to about 60 m. Light levels at dusk (twilight) extend perceptual range still further t o about 90 m. These results suggest that interpatch dispersal by whitefoote d mice would be more successful under greater illumination, but travelling under such conditions entails a considerable risk of predation. These mice might avoid such a conflict by travelling under the cover of darkness with the aid of information gathered remotely during relatively high illuminatio n. We show that mice are indeed capable of such a 'look now and move later' strategy: mice retain directional information gained under bright conditio ns and maintain a previously determined bearing in conditions under which d istant navigational stimuli may be largely absent (e.g. maximal darkness). Ultimately, a better understanding of the behavioural and ecological factor s affecting the movements of animals across landscapes should produce a cle arer picture of the interaction between landscape structure and population ecology. (C) 1999 The Association for the Study of Animal Behaviour.