Identification of distinguishing characteristics around middens of Mount Graham red squirrels

I measured characteristics of vegetation around middens of the endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) in the Pinaleno Mountains of southeastern Arizona. Midden sites were compared to random sites in both the spruce/fir and transition-zone forests. Foliage volume, canopy closure over plot center, volume of downed logs ≥20 cm in diameter, and density of snags >40 cm in diameter at breast height (dbh) were greater at midden sites and best distinguished midden sites from random sites in both forest types. The mean stand age of midden sites was >230 years in the spruce/fir forest and >200 years in the transition-zone forest. As regeneration of disturbed sites will take long periods of time, management applications to protect the red squirrel must focus on preserving existing habitat by limiting activities that remove large trees, snags, or logs, open the forest canopy, create forest edge, or otherwise disrupt forest integrity