Category: Theses and Dissertations
Title: Tassel-eared Squirrel Foraging Patterns and Projected Effects of Ecological Restoration Treatments at Mt. Trumbull, Arizona
Author: Elson, M.T.
Subject: Wildlife, Mt. Trumbull
Abstract: Tassel-eared squirrels (Sciurus aberti) are an important component of southwestern ponderosa pine (Pinus ponderosa) ecosystems. Tassel-eared squirrel habitat has been altered by the interruption ofthe natural fire regime, which maintained low tree densities and diverse stand structures prior to Euro-American settlement. Although ecological restoration efforts seeking to restore presettlement conditions through mechanical thinning and prescribed fire are currently underway in many areas ofthe Southwest, the effects ofrestoration treatments on tassel-eared squirrels are unknown. We selected three experimental blocks at Mt. Trumbull, Arizona, to represent a continuum of stand types prior to ecological restoration. The locations of all tassel-eared squirrel feed trees were mapped in a total of 27 hectares. Data collected on each feed tree included tree status (leave or take) , dbh, number of clipped needle clusters, number of peeled cone cores, number of fungi digs, relative abundance ofold clipped clusters, tree damage, and the presettlement status ofthe tree. We determined the characteristics and spatial pattern of feed trees under current conditions at Mt. Trumbull and predicted changes due to restoration treatments using the marked status of trees. The current prescription resulted in low percentages of the trees currently used for foraging on inner bark being marked for retention in the three treatment units surveyed. Trees selected by squirrels for foraging on ovulate cones were retained at higher percentages . More random spatial distribution and larger average sizes of retained feed trees are predicted. We predict corresponding reductions in squirrel populations, larger home range sizes, and increased seasonal movements. We developed two possible modifications of the current prescription to mitigate impacts on squirrel foraging habitat. The individual tree approach is predicted to significantly reduce impacts on forage availability while having little impact on structural objectives of current prescriptions. It is uncertain, however, whether the availableforage willbe fullyutilized. The patch approach is predicted to have greater benefits for squirrels and is considered a more reliable approach to mitigating impacts. Implementing the patch approach, however, would require fundamental changes in current objectives and marking guidelines-a cost which may outweigh the anticipated benefits.
Publisher: NAU School of Forestry, http://www.for.nau.edu