Fine‐Scale Analysis of Mount Graham Red Squirrel Habitat Following Disturbance

Abstract

Habitat destruction and degradation are major factors in reducing abundance, placing populations and species in jeopardy.Monitoring changes to habitat and identifying locations of habitat for a species, after disturbance, can assist mitigation of the effects of humancaused or -amplified habitat disturbance. Like many areas in the western United States, the Pinaleño Mountains of southeastern Arizona, USA, have suffered catastrophic fire and large-scale insect outbreaks in the last decade. The federally endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is only found in the Pinaleño Mountains, and to assess effects of forest disturbance on habitat we modeled their potential habitat by identifying characteristics of cover surrounding their centrally defended middens. We classified high-spatial resolution satellite imagery into ground cover classes, and we used logistic regression to determine areas used by squirrels. We also used known midden locations in conjunction with slope, elevation, and aspect to create a predictive habitat map. Squirrels selected areas of denser forest with higher seedfall for midden sites. Among active middens, those in the densest and least damaged forests were occupied in more seasons than those in more fragmented and damaged areas. The future conservation of red squirrels and the return of healthy mature forests to the Pinaleño Mountains will rely on preservation of mixed conifer zones of the mountain and active restoration of spruce-fir forests to return them to squirrel habitat. Our ability to evaluate the spectrum of fine-to coarse-scale disturbance effects (individual tree mortality to area wide boundaries of a disturbance) with high-resolution satellite imagery shows the utility of this technique for monitoring future disturbances to habitat of imperiled

Predicting Avian Abundance Within and Across Tidal Marshes Using Fine-Scale Vegetation and Geomorphic Metrics

“…This is one of very few applications of fine-scale aerial imagery-derived vegetation GIS data to predict wildlife abundance and distribution (but see Wood et al 2007), and is the only such known example for marsh breeding birds.…”

“…But with the recent widespread availability of high resolution (1-m or finer) and/or multispectral aerial imagery, there exists a great opportunity to develop fine-scale predictive models that capture local-scale variability within the organism of interest (Kelly and Meentemeyer 2002;Wood et al 2007). In particular, these types of imagery have been used to generate spatially and floristically detailed maps of tidal marsh vegetation (Hirano et al 2003;Judd et al 2007), which may contain more useful information relating to the reproductive and foraging requirements of a species than vegetation indices such as the Normalized Difference Vegetation Index (NDVI).…”

Survey of the Patterns of Nest Box Use Among Squirrels (Sciuridae) in Managed Forest Stands in Clinton County, New York

“…Thinning and other silvicultural management practices have been known to alter the distribution and abundance of small mammals, and adversely affect their survival and reproduction (Wood et al, 2007). The majority (81%) of occupied nest boxes occurred in the reference site, which suggests that flying squirrels are sensitive to logging and natural disturbances (Patterson and Malcolm, 2010).…”

Severely insect-damaged forest: A temporary trap for red squirrels?

“…Graham red squirrels from September 2003 to December 2005 within the insect-damaged, spruce-fir forest (529 ha, 3048-3267 m) in the Pinaleñ o Mountains of southeastern Arizona. The forest was dominated by Engelmann spruce (Picea engelmannii) and cork-bark fir (Abies lasiocarpa) in the upper elevations, but included Douglas-fir (Pseudotsuga menziesii), white fir (Abies concolor), southwestern white pine (Pinus strobiformis), ponderosa pine (Pinus ponderosa), and aspen (Populus tremuloides) in greater numbers as elevation approached 3048 m. Beginning in 1996, all spruce-fir forest (termed 'insectdamaged') in the Pinaleñ os was impacted by insect infestation (Wood et al, 2007). Therefore, we simultaneously collected data in a portion of relatively undamaged mixed-conifer forest (termed 'undamaged'), 130 ha, 2850-2979 m) dominated by cork-bark fir, but that included previously listed species.…”

“…We used the trapping and handling methods of Koprowski et al (2007) to capture and uniquely mark all squirrels, and radio collar all adults (>200 g). We assessed mass, sex, age class, and reproductive status of all squirrels.…”