Young, P. J., V. L. Greer, and S. K. Six. 2002. Characteristics of Bolus Nests of Red Squirrels in the Pinaleño and White Mountains of Arizona. The Southwestern Naturalist 47: 267-275.

Red squirrels (Tamiasciurus hudsonicus) use cavity, bolus, and underground nests for sleeping, protection, and rearing of young. We compared occurrence and structural characteristics of bolus nests at midden sites (area surrounding the central cache) for red squirrels in the Pinaleno Mountains with those in the White Mountains of southeastern Arizona. Bolus nests were more prevalent in the White mountains, possibly as a result of differing habitat structure; forests of the Pinaleno Mountains had significantly (P < 0.05) larger basal area, greater stem densities, and there was less grass on the forest floor than in the White Mountains. Midden sites with more potential cavity nest sites were more likely to have only cavity nests present. Bolus nests were constructed mostly of lichens in the Pinaleno Mountains and of grasses in the White Mountains, whereas most other nest and nest tree characteristics were similar between locations, although nest trees were further from the main cache location at middens in the Pinaleno Mountains.