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Response of Endangered Mt. Graham Red Squirrels to Severe Insect Infestation

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Response of Endangered Mt. Graham Red Squirrels to Severe Insect Infestation Trailblazers in the Forest: Response of Endangered Mt. Graham Red Squirrels to Severe Insect Infestation Item Type text; Electronic Thesis Authors Zugmeyer, Claire Ann Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 23/09/2021 14:33:31 Link to Item http://hdl.handle.net/10150/193336 TRAILBLAZERS IN THE FOREST: RESPONSE OF ENDANGERED MT. GRAHAM RED SQUIRRELS TO SEVERE INSECT INFESTATION by Claire Ann Zugmeyer ________________________ A Thesis Submitted to the faculty of the SCHOOL OF NATURAL RESOURCES In Partial fulfillment of the Requirements For the Degree of MASTERS OF SCIENCE WITH A MAJOR IN WILDLIFE AND FISHERIES SCIENCES In the Graduate College THE UNIVERSITY OF ARIZONA 2007 2 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: ________Claire Zugmeyer_________ APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below: _______________________________________ ______April 27, 2007_____ John L. Koprowski Date Professor of Wildlife and Fisheries Science 3 ACKNOWLEDGMENTS I thank my family for their love and support throughout my thesis research. I am indebted to my advisor John Koprowski, whose guidance, encouragement, enthusiasm, and friendship were critical components in the completion of this research. I also thank my committee members, Courtney Conway and R. William Mannan, for their helpful advice and direction. I would like to thank Sadie Bertelsen, Debbie Buecher, Seafha Blount, Kathi Borgmann, Nichole Cudworth, Sandy Doumas, Andrew Edelman, Aaron Flesch, Erika Geiger, Vicki Garcia, Vicki Greer, Nate Gwinn, Sky Jacobs, Julia Jolley, Sarah King, Kate Leonard, Andrea Litt, Melissa Merrick, Karen Munroe, Danielle O’Dell, Mark Ogonowski, Geoff Palmer, Bret Pasch, Kitty Pokorny, Nicolas Ramos- Lara, Mags Rheude, Bob Steidl, Eric Wallace, Marissa Watson, Bruce Weise, Ryan Wilson, David Wood and past University of Arizona Red Squirrel Monitoring Program employees for valuable assistance and support throughout the project. Field efforts were conducted under permits from the USDA Forest Service, Arizona Game and Fish Department, US Fish and Wildlife Service, and the University of Arizona’s Institutional Animal Care and Use Committee. Special thanks to Bill Van Pelt, Arizona Game and Fish Department, for his efforts to procure funds. Funding and in-kind support for this research were provided by Arizona Game and Fish Department, U. S. Department of Agriculture, U. S. Forest Service, University of Arizona’s Office of the Vice President for Research, Steward Observatory, Arizona Agricultural Experiment Station, and T&E Incorporated. 4 TABLE OF CONTENTS LIST OF TABLES………………………………………………………………………...7 LIST OF FIGURES……………………………………………………………………….8 ABSTRACT………………………………………………………………………………9 CHAPTER 1: INTRODUCTION………………………………………………………..10 CHAPTER 2: PRESENT STUDY………………………………………………………12 REFERENCES…………………………………………………………………………..14 APPENDIX A: UNALTERED HABITAT SELECTION AFTER SEVERE INSECT INFESTATION: CONCERNS FOR FOREST-DEPENDENT SPECIES ……………..16 Abstract…………………………………………………………………….……16 Introduction……………………………………………………………………...17 Methods………………………………………………………………………….21 Study area……………………………………………………………….21 Midden occupancy………………………………………………………21 Midden characteristics…………………………………………………..22 Level of insect damage…………………………………………………..23 Statistical analyses………………………………………………………23 Results…………………………………………………………………………...25 Midden occupancy………………………………………………………25 5 TABLE OF CONTENTS – Continued Midden characteristics…………………………………………………...25 Midden microclimates……………………………………………………27 Level of insect damage…………………………………………………..28 Discussion………………………………………………………………………..29 References………………………………………………………………………..33 APPENDIX B: SEVERELY INSECT-DAMAGED FOREST MAY FUNCTION AS AN ECOLOGICAL TRAP FOR RED SQUIRRELS………………………….…………….42 Abstract…………………………………………………………………………..42 Introduction…………………………………………………………….………..43 Methods………………………………………………………………….….…..45 Model organism and system…………………………………………….45 Study area and trapping…………………………………………………46 Habitat preference………………………………………………………47 Home range and space use………………………………………………47 Body mass and demography……………………………………………..49 Statistical analyses……………………………………………………….50 Results……………………………………………………………………………51 Habitat is available in healthy and insect-damaged forest ……………..51 Habitat selection in areas with less damage……………………………..52 Home ranges enlarge…………………………………………………….54 Body mass did not differ…………………………………………………55 6 TABLE OF CONTENTS – Continued Demographic differences exist…………………………………………...55 Discussion………………………………………………………………………..56 References………………………………………………………………………..61 7 LIST OF TABLES TABLE 1. Mean (± SE) physical and vegetation measurements for random locations (n = 26), and Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) unoccupied middens (n = 28), and occupied middens (n = 18) in the insect-damaged forest………..39 TABLE 2. Results of step-wise logistic regression models to assess odds of a) a site being a Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) midden (n = 46) or random location (n = 26), or b) a midden being occupied (n = 18) or unoccupied (n = 28) in the insect-damaged forest……………………………………………………….40 TABLE 3. Seasonal fluctuations in mean 95% range and 50% core (± SE) for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest………………………………………………………………………….….68 TABLE 4. Mean 95% range and 50% core (± SE) for male and female Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest in the Pinaleño Mountains…………………………………………………………….…….69 8 LIST OF FIGURES FIGURE 1. Mean (± SE) a) maximum, b) minimum, and c) maximum daily range of ground surface temperature from September 2004 to August 2005 for random locations and unoccupied and occupied Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) middens in insect-damaged forest……...………………………………....41 FIGURE 2. Seasonal fluctuations in mean percent pixels (± SE) classified as a) dead trees and b) open areas, within ranges, cores, and random areas for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged forest in the Pinaleño Mountains……………………………………………………………..……….70 FIGURE 3. Seasonal fluctuations in mean number of pixels (± SE) classified as a) live and b) dead trees, within ranges, cores, and random areas for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged forest in the Pinaleño Mountains………………………………………………………………………..……....71 FIGURE 4. Mean body mass (± SE) for adult male and female Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest in the Pinaleño Mountains……………………………………………………………………...72 FIGURE 5. Proportion of Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) surviving since first captured in insect-damaged and healthy forests in the Pinaleño Mountains…...…………………………………………………………………73 9 ABSTRACT I examined habitat selection of middens within insect-damaged forest and compared home range and survival for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest. Squirrels used habitat in areas with <69% tree mortality. Basal area, canopy cover, and log volume were greater at middens than random locations. Within midden sites, only greater basal area of live trees distinguished occupied sites from unoccupied sites. Surface temperature at occupied middens tended to be cooler than unoccupied middens. Squirrels living in insect-damaged forest had larger home ranges than in healthy forest. Squirrel body mass and reproductive condition did not differ between forest types, suggesting that insect- damaged forest provided adequate resources. However, squirrels inhabiting insect- damaged forest experienced lower survivorship and 50% fewer potential reproductive events than squirrels in healthy forest, implicating presence of an ecological trap. Preservation of remaining healthy forest is a priority for management of this endangered species. 10 CHAPTER 1: INTRODUCTION Disturbance creates temporal and spatial heterogeneity of resources that can cause short- and long-term changes to habitat and disrupt interactions between individuals and resources (Sousa 1984). Severe disturbance may dramatically alter habitat structure, causing reduced reproductive success or site abandonment (Jones et al. 2001, Penteriani et al. 2002). Rates and impacts of natural disturbances are predicted to increase with current trends in climate change (Dale et al. 2000), thus
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