Edelman, A. J. and J. L. Koprowski. 2005. Selection of drey sites by Abert's squirrels in an introduced population. Journal of Mammalogy 86(6): 1220-1226.

thackerk1 — Tue, 25 Jun 2019 01:24:39 +0000

Authors

Andrew J. Edelman

John L. Koprowski

Abert’s squirrels (Sciurus aberti) are reported to depend on ponderosa pine (Pinus ponderosa) for food and nest sites. Introduced Abert’s squirrels in the Pinaleño Mountains of Arizona, however, occupy mixed-conifer forests that contain almost no ponderosa pine (about 2%). We examined selection of drey sites in this introduced population. Dreys (i.e., spherical nests) were built adjacent to the trunk at 75% of the tree height. Dreys were found in 5 different conifer species and ,2% were in ponderosa pine. Drey trees were larger and had more access routes than did random trees. Drey sites were steeper, had more large trees, Douglas-fir (Pseudotsuga menziesii), and southwestern white pine (Pinus strobiformis), and less corkbark fir (Abies lasiocarpa var. arizonica) than random sites. The structural characteristics of drey trees in the Pinalen ̃os population also were very similar to drey trees used by natural populations of Abert’s squirrels in ponderosa pine forests. Our results suggest that the dependence of Abert’s squirrels on ponderosa pine is not as strong as previously reported. Structural features such as tree size and access routes appear to be more important to selection of drey sites than tree species.

Additional Information

Selection of Drey Sites by Abert's Squirrels in an Introduced Population

Date of publication:

2005

Topics

Mount Graham Red Squirrel

Abert’s squirrels

nest-site selection

Pinaleño Mountains

exotic species

bolus nest

tassel-eared squirrel

obligate

Edelman, A. J., J. L. Koprowski, and S. R. Bertelsen. 2009. Potential for nest site competition between native and exotic tree squirrels. Journal of Mammalogy 90: 167-174.

thackerk1 — Tue, 25 Jun 2019 00:54:50 +0000

Authors

Andrew J. Edelman

John L. Koprowski

Sadie R. Bertelsen

In communities where strong interspecific competition between native species is lacking, exotic and native species often exhibit intense resource competition resulting in decline of native populations. We examined the potential for interspecific competition for nest sites between co-occurring native Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) and exotic Abert’s squirrels (Sciurus aberti) in the Pinaleño Mountains of Arizona. Comparison of nest use between red and Abert’s squirrels at different scales (nest, nest tree, and nest site) revealed contrasting results. Competition for nests and nest trees appears unlikely given the dissimilarity in use of nest types and tree characteristics. Abert’s squirrels predominately used dreys, whereas red squirrels mostly used cavity nests. Neither squirrel species occupied a nest used by the other species. Nest trees differed in size and species between squirrels for dreys, but not for cavities. Abert’s squirrel nest sites were found in a wider range of microhabitats including almost all microhabitats in which red squirrel nest sites were located. Although there was significant overlap, each species showed distinct trends in microhabitat. In general, red squirrel nest sites were characterized as more densely forested areas dominated by corkbark fir (Abies lasiocarpa var.arizonica), whereas Abert’s squirrel nest sites were more open and contained greater tree species diversity. Overlap in microhabitat characteristics increases the likelihood of interspecific competition and could increase the vulnerability of red squirrels to extinction.