Lichens as Nesting Material for Northern Flying Squirrels in the Northern Rocky Mountains

Abstract

We examined the composition of nest material used by northern flying squirrels (Glaucomys sabrinus) occupying artificial nest boxes in central Idaho and western Montana. Nests were constructed almost entirely of arboreal lichens (96% lichen by volume). In both regions, three species of Bryoria dominated nesting material although a total of 15 species of lichens were identified in 159 nest samples from central Idaho. Species of lichens used for nests differed across four types of forest vegetation. Nests in stands of lodgepole pine (Pinus contortd) had more Bryoria fremontii and less B. pseudofuscescens than nests in other forest types. The rank-order abundance of lichens used in nests was related to the rank-order abundance of lichens collected from forests at nest sites, although the relationship was not strong. We suggest that lichen nests may function to reduce thermal energy expenditures during winter or act as food caches. The dominant lichen used in nests lacked acids and other secondary compounds found in other arboreal lichens and, thus, may be more palatable to squirrels.