Nest-site selection by the harvest mouse Micromys minutus in seasonally changing environments

Abstract

We studied nest-site selection of harvest mice Micromys minutus (Pallas, 1771) for clarifying plant community characters suitable for nesting. We surveyed newly constructed nests in a marsh population and various plant characters likely to affect nest-site selection throughout the breeding season. The harvest mouce used common reed Miscanthus sacchariflorus and Japanese pampas grass Miscanthus sinensis more frequently than expected by the propotions of their areas occupied in summer, but shifted to Carex confertiflora after October. Although reed grass Phragmites communis was dominant in the marsh, mice did not choose this species. The 2 grass species selected in summer had a larger number of leaves per unit area, and the most selected species had a higher stem density. Both of these plant traits indicate a richness of nesting materials. The rapid increase in selection for Carex from autumn to winter was likely due to its leaf freshness and/or flexibility, as leaves of Carex maintained a high level of chlorophyll content until winter. The harvest mouse appeared to flexibly change its selection for nesting plants in response to seasonal environmental changes. We also discuss the implications of our findings in terms of harvest mouse habitat conservation.