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Spatial Ecology of the Giant Kangaroo Rat (Dipodomys Ingens): a Test of Species Distribution Models As Ecological Revealers

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Spatial Ecology of the Giant Kangaroo Rat (Dipodomys Ingens): a Test of Species Distribution Models As Ecological Revealers Spatial Ecology of the Giant Kangaroo Rat (Dipodomys ingens): A Test of Species Distribution Models as Ecological Revealers by William Timothy Miles Bean A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Environmental Science, Policy and Management in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Justin S. Brashares, Chair Professor Steven Beissinger Professor William Lidicker Fall 2012 Spatial Ecology of the Giant Kangaroo Rat (Dipodomys ingens): A Test of Species Distribution Models as Ecological Revealers © 2012 by William Timothy Miles Bean Abstract Spatial Ecology of the Giant Kangaroo Rat (Dipodomys ingens): A Test of Species Distribution Models as Ecological Revealers by William Timothy Miles Bean Doctor of Philosophy in Environmental Science, Policy and Management University of California, Berkeley Professor Justin S. Brashares, Chair Monitoring a species’ distribution and abundance is a critical component in both applied and theoretical ecology. Wildlife managers demand effective and efficient methods for monitoring species of concern. Theoretical ecologists, as well, need accurate estimates of species’ distributions and abundance, and measures of the quality of habitat that determines these parameters. Recent advances in species distribution models have suggested an inexpensive and robust way forward for estimating habitat suitability, but these models have rarely addressed species distributions at ecologically relevant spatial or temporal scales. Further, few studies have examined the relationship between habitat suitability, as estimated from species distribution models, and habitat quality, a better predictor of long-term population persistence. In this study, I (1) test current methods for monitoring giant kangaroo rat population extent and abundance; (2) create novel species distribution models that incorporate primary productivity as an ecological predictor for giant kangaroo rat distribution; and (3) test whether these models are actually related to independent measures of habitat quality. Aerial surveys are shown to be a reliable estimator for giant kangaroo rat population extent. Burrow counts may be a reliable index of long-term population size, but are inadequate to detecting short-term changes in size or growth. Distribution models that incorporate ecologically relevant variables on annual time scales are shown to better predict giant kangaroo rat distribution than static models that assume the species is at equilibrium. Finally, species distribution models perform well at measuring long-term giant kangaroo rat abundance, and temporally explicit models predict short-term abundance, but species distribution models are generally incapable of adequately distinguishing between high and low quality habitat as measured by survival or body condition. 1 Dedication I am not certain why anybody would stick around while I counted rats from space, but Piper Bean, you did. Your support, care and understanding are the reason this study exists. I, and the giant kangaroo rats, thank you for your sanity and grace. I thank my parents, William and Barbara Bean, for giving me a curiosity in, and care for, the world around us. And finally, to my sisters, Meg Salgado and Amanda Bean, for leading the way down the trail. i Table of Contents CHAPTER 1. INTRODUCTION..............................................................................................................1 LITERATURE CITED ...................................................................................................................................................3 CHAPTER 2. AN EVALUATION OF MONITORING METHODS FOR THE ENDANGERED GIANT KANGAROO RAT........................................................................................................................5 ABSTRACT ...................................................................................................................................................................5 INTRODUCTION ..........................................................................................................................................................5 METHODS....................................................................................................................................................................7 Study Area ............................................................................................................................................................... 7 Estimating Distribution Extent...................................................................................................................... 7 Estimating Animal Density .............................................................................................................................. 8 RESULTS ......................................................................................................................................................................9 Estimating Distribution Extent...................................................................................................................... 9 Estimating Animal Density ............................................................................................................................10 DISCUSSION..............................................................................................................................................................10 LITERATURE CITED ................................................................................................................................................12 TABLES .....................................................................................................................................................................14 FIGURES....................................................................................................................................................................15 CHAPTER 3. MULTI-STEP REALIZED DISTRIBUTION MODELS SUGGEST BOTTOM-UP CONTROL OF POPULATION EXTENT IN AN ENDANGERED RODENT.................................. 18 ABSTRACT ................................................................................................................................................................18 INTRODUCTION .......................................................................................................................................................18 METHODS.................................................................................................................................................................20 Study Site and Focal Species..........................................................................................................................20 Potential Distribution Modeling..................................................................................................................21 Realized Distribution Modeling ...................................................................................................................23 RESULTS ...................................................................................................................................................................25 Potential Distribution Modeling..................................................................................................................25 Realized Distribution Modeling ...................................................................................................................25 DISCUSSION..............................................................................................................................................................25 LITERATURE CITED ................................................................................................................................................28 TABLES .....................................................................................................................................................................33 FIGURES....................................................................................................................................................................35 CHAPTER 4. SPECIES DISTRIBUTION MODELS PREDICT ABUNDANCE BUT NOT SURVIVAL AT MULTIPLE SCALES ................................................................................................... 38 ABSTRACT ................................................................................................................................................................38 INTRODUCTION .......................................................................................................................................................38 METHODS.................................................................................................................................................................40 Study Sites .............................................................................................................................................................40 Measures of Habitat Quality..........................................................................................................................40 Range-wide Distribution Model...................................................................................................................42 Local Distribution Model ................................................................................................................................42
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