Doumas, S. L., J. L. Koprowski, and W. O. Noble. 2016. Landscape-level assessment of Abert's squirrel and red squirrel in mixed conifer forest. The Southwestern Naturalist 60:240-246.

We examined feeding sign of Abert’s squirrels (Sciurus aberti) and red squirrels (Tamiasciurus hudsonicus) each spring 2005–2009 in mixed conifer forests in northern Arizona, USA. We used high- resolution aerial photographs to assess vegetation characteristics where feeding sign surveys were conducted and analyzed the association of feeding sign frequency to vegetation characteristics to compare and contrast species habitat use. At the landscape level, we found considerable overlap in characteristics of forests used by the two species of native tree squirrels. Red squirrels used denser forests with fewer and smaller gaps than do Abert’s squirrels, and Abert’s squirrels used more ponderosa pine (Pinus ponderosa) than do red squirrels.