Geographical information systems (GISs) have been applied in a number of wildlife habitat studies (Tomlin et al., 1980; Reed, 1980; Donovan et al., 1987; Hodgson et al., 1988; Agee et al., 1989), but these studies have focused on how animals respond to their environment rather than how they affect it. Animal effects on the landscape are typically diffuse in both time and space, making them difficult to quantify with or without a GIS. Techniques exist for monitoring animal presence and for mapping environmental conditions, but techniques for monitoring the cumulative effects of an animal population at the landscape scale are generally lacking. Remote sensing and aerial photography can provide mappable evidence of animal influences for GIS analysis, but only if those influences are large and distinctive enough to be detected remotely, and can be positively attributed to animal activities (e.g. insect defoliation outbreaks).