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13. Management and Conservation of Tassel-Eared Squirrels
- University of New Mexico Press
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157 Management and Conservation of Tassel-Eared Squirrels Results of research from several state and federal agencies confirm that squirrels need a certain size, density, and arrangement of ponderosa pine to survive and reproduce. In turn, there is evidence that squirrels and other small animals recycle nutrients that contribute to the health of ponderosa pine. The Abert’s squirrel and other small rodents have notcaused damagetotheextentpredicted byforestersintheearly1900sandbotharepartofanecosystemthat has been functioning for thousands of years. It appears, from what we now know, discounting dramatic climatic change, that future generations will continue to enjoy both the Abert’s squirrels and ponderosa pine for another several thousand years. —D. R. Patton, “The Fort Valley Experimental Forest, Ponderosa Pine and Wildlife Habitat Research,” 2008 Introduction Ponderosa pine forests were deemed to be endangered ecosystems in a 1995 assessment of ecosystems conducted for the National Biological Survey (ref. 1). Almost twenty years earlier, Pederson and his colleagues in Utah recommended in a paper addressing habitat requirements of tassel-eared squirrels that “the forest should be managed solely for the propagation and enhancement of this unique animal” (ref. 2). David Brown emphatically declared in a 1986 Arizona Game and Fish Department publication, “Actually, it is the forester whose tree management threatens the squirrel” (ref. 3). Important benefits of tassel-eared squirrels with respect to forest management practices are: squirrels are 13 158 C H A P T E R T H I R T E E N watchable wildlife, squirrels are a prey species for northern goshawks, and squirrels spread spores of mycorrhizal fungi in their feces (ref. 4). In the early 1960s, Abert’s squirrels were dismissed as game animals or even forest pests (ref. 5). But by 1999, their importance was considerably more understood as tassel-eared squirrels were referred to as “ecological barometers” and “windows” that could be used to assist researchers in understanding the intricate relationships within the ponderosa pine forest ecosystem (ref. 6). And now tassel-eared squirrels are recognized as a management indicator species (MIS) because of their narrow habitat association with ponderosa pine forests and because they can be monitored to indicate the effects of a particular management practice (ref. 7, 8, 9). Management of the southwestern ponderosa pine forests for recreation , maintaining all the floral and faunal components, livestock grazing, fire prevention, and timber harvesting, presents administrative and bureaucratic challenges. Conflicts occur when goals are contradictory . For example, thinning of the ponderosa pine forests in restoration efforts to reduce forest fires also reduces basal area and interlocking branches of the canopy. This forest management treatment alters those two components of squirrel habitat, thus affecting tassel-eared squirrel populations. This chapter reviews the practices, management studies, and current recommendations for habitat for tassel-eared squirrels in ponderosa pine forests. Basal Area and Tree Density Basal area is the cross-sectional measurement of trees in a given area (m2 /ha). Basal area and the number of Kaibab squirrel nests in a virgin ponderosa pine forest were used to develop a model that predicted a top rating for habitat quality if the basal area was 40 m2 /ha with eight nests and a poor rating for habitat quality if the basal area was 28 m2 /ha with two nests (ref. 10). Another study recommended maintaining areas with basal areas of > 35 m2 /ha, especially in areas with large trees (30.5–61.0 cm dbh), for preserving quality habitats for squirrels, because this “may reflect a threshold where further wide-scale reduction of squirrel habitat structural attributes and landscape diversity impact squirrel populations and genetic viability” (ref. 11). Patton developed a squirrel habitat model, using data from two other tassel-eared squirrel studies that were conducted in Arizona (ref. 10, 12). [18.116.20.177] Project MUSE (2024-04-18 00:33 GMT) M a n a g e m e n t a n d C o n s e r v a t i o n 159 He rated the model from optimum quality class g poor quality class. To achieveagoodqualityclassrating,theremustbe>296trees/hawithastand dbh > 30 cm. The trees should be in groups of at least six with interlocking canopies with nest trees and have a dbh range of 28–41 cm dbh (ref. 13). Similar values of good habitat quality with respect to dbh (30–40 cm) werefoundinastudyontreeandsquirreldensitiesintheCarsonNational Forest in New Mexico (ref. 14). Landscape Models In 2006, Prather and his colleagues developed four landscape models that can be used to predict the influence of forest structure on...