The Natural History of Tassel-Eared Squirrels

Contents

Contents ILLUSTRATIONS xiii ACKNOWLEDGMENTS xvii AUTHOR’S NOTES xix CHAPTER ONE: INTRODUCTION 1 [References for Chapter One 4] CHAPTER TWO: PHYSICAL CHARACTERISTICS OF TASSEL-EARED SQUIRRELS 5 Tassels 5 Physical Characteristics—Pelage and the Colors 6 Colors of the Type Specimens of S. a. aberti and S. a. kaibabensis in Arizona 6 Colors of S. a. ferreus in Colorado 6 Colors of S. a. aberti, S. a. chuscensis, and S. a. kaibabensis from Arizona and New Mexico 8 Colors of Tassel-Eared Squirrels from Mexico 9 Genetics of Pelage Colors 9 Guard Hair 10 Dorsal Patch 10 Lateral Stripe 10 Tail Colors 10 Tail Lengths 11 Faces 11 Molting 11 Physical Characteristics—Body Measurements 11 Size 11 Feet and Claws 12 Teeth 14 Cranium Measurements 16 viii C O N T E N T S Determining the Differences between Juveniles and Adults by Physical Characteristics 16 Do Tassel-Eared Squirrels Conform to Allen’s and Bergmann’s Rules? 17 Temperatures of Tassel-Eared Squirrels 17 Future Research 18 [References for Chapter Two 18] CHAPTER THREE: HABITAT, HOME RANGE, AND DISTRIBUTION 21 Introduction 21 Habitat 21 Home Range 27 Geographical Distribution of Tassel-Eared Squirrels 30 Natural Range Expansions of Tassel-Eared Squirrels 31 Transplants of Tassel-Eared Squirrels 32 Summary 34 Future Research 34 [References for Chapter Three 34] CHAPTER FOUR: FOOD AND FEEDING ACTIVITIES 38 Introduction 38 Inner Bark of Ponderosa Pine Terminal Shoots 39 Selection of Feeding Trees 42 Is It the Tree Chemistry? 43 Is It a Physical Characteristic? 43 Do Squirrels Rotate the Use of Feed Trees? 45 Do Feed Trees and Non-Feed Trees Have Different Growth Rates? 46 Seeds from Ovulate Ponderosa Pine Cones 46 Mycophagy 47 Other Foods Obtained from Ponderosa Pine Trees 48 Other Foods Used by Tassel-Eared Squirrels 49 Water 49 Food Caching 51 Summary 52 [References for Chapter Four 52] CHAPTER FIVE: NESTS 56 Introduction 56 Types of Nests 57 Bolus Nests 57 Other Types of Nests 60 C O N T E N T S ix Nest Tree Characteristics 61 Summary 62 [References for Chapter Five 63] CHAPTER SIX: BEHAVIOR AND SOCIAL INTERACTIONS 66 Introduction 66 Daily Activity 66 Social Interactions 69 Mating 70 Nesting Behavior 72 Movement within the Forest 73 Activities During Storms 74 Other Behaviors Demonstrated by Tassel-Eared Squirrels 75 Summary 76 Future Research 76 [References for Chapter Six 76] CHAPTER SEVEN: REPRODUCTION, EMBRYOLOGY, AND DEVELOPMENT 79 Introduction 79 Estrus 80 Copulation 82 Gestation and Postnatal Development 83 Lactation 86 Female Reproduction 86 Anatomy 86 Oogenesis 86 Male Reproduction 87 Anatomy 87 Spermatogenesis 89 Sperm Morphology 89 Reproductive Anomalies 89 Future Research 89 [References for Chapter Seven 90] CHAPTER EIGHT: MORTALITY AND PARASITES 93 Introduction 93 Predation 93 Avian Predators 94 Terrestrial Predators 96 Mortality from Habitat Loss 96 Season and Mortality 96 x C O N T E N T S Highway Mortalities 97 Hunting 97 Parasites 98 Other Causes of Mortality 100 Life Span 100 Summary 101 Future Research 101 [References for Chapter Eight 101] CHAPTER NINE: GENETICS 105 Introduction 105 Karyotypes and Chromosomes 105 Serum Proteins 107 Transferrin 107 Albumin 107 T-cell Receptor Genes 108 Major Histocompatibility Complex 110 Genetics and Pelage Color 110 Nucleotide Diversity Using Mitochondrial DNA 111 Cytochrome b Gene 112 Microsatellites 112 Summary 113 Future Research 113 [References for Chapter Nine 114] CHAPTER TEN: THE KAIBAB SQUIRREL 116 Introduction 116 Historical Overview of Kaibab Squirrel Protection 118 The Controversy of the Status—Endangered or Threatened? 120 Transplants of Kaibab Squirrels 124 Summary 124 Future Research 124 [References for Chapter Ten 125] COLOR PLATES Following page 128 CHAPTER ELEVEN: ECOLOGY 129 Introduction 129 Ecology of Tassel-Eared Squirrels and Ponderosa Pines 130 Tassel-Eared Squirrels and Ponderosa Pine Tree Morbidity and Mortality 130 Alternation of Feed Tree Selection 132 C O N T E N T S xi Tassel-Eared Squirrels as Agents of Selection of Ponderosa Pine Trees 133 Nitrogen Cycling 133 Ecology of Tassel-Eared Squirrel Digs 134 Ecology of Tassel-Eared Squirrels and Fungi 134 Tassel-Eared Squirrel Interactions with Other Animals 135 Population Ecology 138 Summary 138 Future Research 139 [References for Chapter Eleven 140] CHAPTER TWELVE: CENSUS AND MONITORING METHODS AND TECHNIQUES 144 Introduction 144 Squirrel Census Methods 144 Evidence of Feeding Activities 144 Hunter Success 146 Forest Characteristics 147 Nest Counts 147 Track Pans 147 Tracks in...