2014 Volume 54 Issue 2 Pages 243-249
Sympatric species with similar ecological characteristics can change their selection of resources to avoid competition. To gain knowledge to clarify the mechanisms of this avoidance, we surveyed nest height change of the small Japanese field mouse Apodemus argenteus to avoid competition with the Siberian flying squirrel Pteromys volans, which, like the mice, nests in tree cavities. We used two types of nest boxes: one with a small-sized entrance that only the mouse can use, and another with a large-sized entrance usable by both rodent species. The heights of the two types of nest boxes used by mice were compared. Mice nested in small-entrance boxes at various heights. Among the large entrance boxes, however, they only nested in those placed at relatively low heights. Generally, predation risk to cavity nesters increases with decreasing nest height, and larger entrances allow raids by potential predators. Thus, it is not likely that the mice prefer to nest in large entrance boxes installed at lower heights where predation risks are expected to be higher. These results suggest that small Japanese field mice change their nest height to avoid nesting resource competition with Siberian flying squirrels.
