Ecology of Free-Living Cats Exploiting Waste Disposal Sites
Total Page：16
File Type：pdf, Size：1020Kb
0 ECOLOGY OF FREE-LIVING CATS EXPLOITING WASTE DISPOSAL SITES DIET, MORPHOMETRICS, POPULATION DYNAMICS AND POPULATION GENETICS ELIZABETH ANN DENNY B.A. M.Litt. A Thesis submitted for the Degree of Doctor of Philosophy School ofBiological Sciences U ni versity of Sydney 2005 CERTIFICATE OF ORIGINALITY I hereby declare that this submission is my own work and to the best of my knowledge it contains no material previously published or written by another person, nor material which to a substantial extent has been accepted for the award of any other degree or diploma at the University of Sydney or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at the University of Sydney or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged. ~:- Elizabeth Ann Denny November, 2005 ABSTRACT The free-living domestic cat (Felis catus), a feral predator in Australia, occupies the entire continent and many offshore islands. Throughout the Australian landscape are rubbish tips, which provide biological attraction points around which free-living cats congregate in high densities. This study examined populations of cats exploiting tip sites in two contrasting bioregions in New South Wales. The study determined the most useful methods for the detection and assessment of abundance of free-living cats, and compared the efficacy of the detection methods between contrasting environments. The diet, morphometries, population dynamics and population genetics of two populations of tip cats at Oberon and Tibooburra were investigated and the tip populations compared to each other and to cats Iiving away from the tip sites. Trapping and observational data together with genetic analysis provided a broad-base for the investigation of the population dynamics of the cats from both study areas. The data showed that the densities of cats at the tip sites were higher than densities recorded for free-living cats elsewhere in Australia, including offshore islands. Introduced rodents comprised a large proportion of the diet of cats living at and away from the tip sites, and the tip cats also relied heavily on putrescible rubbish. It was determined that parameters other than weight are the best measure of the size of cats, and femur length is suggested as the most accurate measure for comparing sizes of free-living cats. The sex ratio of adult cats was close to equality. Females had up to two litters per year and the non-breeding period was longer in the colder, wetter Oberon environment than in the warmer, drier Tibooburra environment. Kitten survival rates at the tip sites were relatively high ("' 60%) compared to other studies. The tip populations comprised long-term resident cats, with occasional immigrants, and the migration rates were weak and female-biased. Female kin groups were identified at both tip sites and the larger lineages were assigned parentage for most of the tip offspring. Paternity assessment suggested the possibility of multiple paternity for individual litters, and the most likely fathers were predominantly larger males. The tip sites provide unique habitats within the surrounding landscape, around which free-living cats congregate in high densities, forming structured social groups based on matrilineal lines, with males more loosely attached. The supplementary food resources at tip sites, the high cat densities, relatively high kitten survival rates and movements and migration away from the tips suggest that tip sites play an important role in the ecology of free-living cats in Australia. The tip sites also provide the opportunity for ongoing control programs that may substantially reduce the abundance of free-living cats on the Australian mainland. ii ACKNOWLEDGEMENTS I acknowledge with gratitude the following: My supervisor Professor Christopher Dickman, for accepting me as a student, for his constructive criticism and assistance with my research, and for his photographic memory of research papers. I also wish to thank all the members of the Dickman Lab with whom I shared discussions, coffees and funny times. In particular, I thank Dr Mathew Crowther for his assistance with the identification of mammal teeth (and for always being available for coffee). My associate supervisor Dr Stuart Gilchrist for allowing me access to the Fruit Fly Lab and for his advice and assistance with my project. I thank Dr Alfie Meats for convincing me to conduct the genetic analysis myself. I also wish to thank all the members of the Fruit Fly Lab for their advice, assistance and friendship. In particular I thank Van Pham for teaching me the laboratory techniques required. My associate supervisor Dr Jack Giles for supplying office space at Taronga Zoological Park and for advice and assistance (and guitar recitals). The Oberon Council for access to the tip site. In particular, I thank the late Mr Richard Swannell for his enthusiasm, advice and assistance. The officers of the Department of Environment and Conservation (Oberon), in particular Chris Banffey for assistance with trapping. I also thank officers of the Jenolan Caves Reserve Trust. All the Officers of the Department of Environment and Conservation (Tibooburra). In particular, I thank Lars Kogge, for accommodation in "The Swamp" during field trips. I thank Dan Hough for his interest, enthusiasm and assistance and John Jackson for discussions, advice and laughs. All of the residents of Tibooburra for their friendship over many years. My particular thanks to Joss and Barney Davie. Tigger Wise for her keen eye and superior language skills. My husband, Dr Martin Denny, for his unfailing support, for sharing his knowledge, for listening to my complaints and for spending time as the unpaid field assistant. I thank my daughters Kate and Emma Denny for having faith in my ability, encouraging me always and keeping up the humour. iii TABLE OF CONTENTS CHAPTER 1 INTRODUCTION 1.1 INTRODUCTION 1.2 WORLDWIDE FELID DISTRIBUTION 5 1.3 BRIEF HISTORY OF CATS IN AUSTRALIA 7 1.4 CAT IMPACTS ON NATIVE FAUNA IN AUSTRALIA 10 1.5 STATUS AND MANAGEMENT OF CATS IN AUSTRALIA 12 1.5.1 Legislation 13 1.5.2 Cat Control Programs 14 1.6 CAT ECOLOGY 18 1.6.1 Cat Diet 18 1.6.2 Cat Densities and Resources 21 1.6.3 Social Structure of Cats 24 1.7 GENETICS AND ECOLOGY 26 1.8 SCOPE OF THE THESIS 30 1.9 AIMS AND HYPOTHESES 31 1.10 STRUCTURE OF THE THESIS 33 CHAPTER2 STUDY SITES 36 2.1 STUDY AREAS 36 2.1.1 Oberon 36 2.1.1.1 Location 36 2.1.1.2 Climate 36 2. 1.1.3 Landforms 39 2.1. 1.4 Vegetation 39 2.1.1.5 Land use 40 2.1. 1.6 Selection of study sites 41 (i) Oberon waste disposal site 42 (ii) Oberon township 42 iv Table of contents (iii) Oberon farmland 43 (iv) Jenolan Caves Reserve 43 (v) Kanangra-Boyd National Park 43 2.1.2 Tibooburra 46 2.1.2.1 Location 46 2. 1.2.2 Climate 48 2.1.2.3 Landforms 49 2.1.2.4 Vegetation 50 2.1.2.5 Land Use 50 2.1.2.6 Selection of Study Sites 51 (i) Tibooburra waste disposal site 52 (ii) Tibooburra village 53 (iii) Tibooburra common 53 (iv) Tibooburra grazing properties 53 (v) Sturt National Park 54 2.2 STUDY PERIOD 54 CHAPTER3 DETECTION AND RELATIVE ABUNDANCE 58 3.1 INTRODUCTION 58 3.2 METHODS 58 3.2.1 Non- trapping Sampling 58 3.2.1.1 Tracks, tree scratches and kills 58 3.2.1.2 Scat counts 60 3.2.1.3 Spotlighting 61 3.2.1.4 Community consultation 62 3.2.2 Trapping 64 3.2.3 Data Analysis 67 3.3 RESULTS 68 3.3.1 Non-trapping Sampling 68 3.3.1.1 Tracks, tree scratches and kills 68 4.3.1.2 Scat counts 69 v Table of contents 3.3.1.3 Spotlighting 70 3.3.2 Trapping 71 3.3.2.1 Trap rates at tip sites 71 3.3.2.2 Seasonal trap rates at tip sites 72 3.3.2.3 Trap rates away from tip sites 73 3.4 DISCUSSION 74 3.4.1 Non-trapping Methods 74 3.4.2 Trapping 79 3.5 CONCLUSIONS 83 CHAPTER4 DIET 86 4.1 INTRODUCTION 86 4.2 METHODS 87 4.2.1 Scat Collection 87 4.2.2 Scat Components 88 4.2.4 Small Mammal Sampling 89 4.2.5 Data Analysis 90 4.3 RESULTS 92 4.3.1 Scat Analysis 92 4.3.1.1 Oberon 92 4.3.1.2 Tibooburra 94 4.3.2 Comparison of Diet Components from Oberon and Tibooburra Tips 97 4.3.3 Seasonal Variation in Diet 98 4.3.4 Species Composition in Scats 100 4.3.6 Tooth and Hair Analysis 102 4.3.7 Small Mammal Trapping 104 4.4 DISCUSSION 105 4.4.1 Scat Collection 105 4.4.2 Scat Identification 107 4.4.3 Scat Analysis 108 VI Table of contents 4.4.4 Dietary Analysis 109 4.5 CONCLUSIONS 119 CHAPTER 5 MORPHOMETRICS 121 5.1 INTRODUCTION 121 5.2 METHODS 121 5.2.1 Anaesthesia and Processing 122 5.2.2 Body Measurements and Coat Colour 122 5.2.3 Collaring and Marking 123 5.2.4 Release of Captured Animals 124 5.2.5 Data Analysis 124 5.3 RESULTS 125 5.3.1 Anaesthetics and Processing 125 5.3.4 Body Measurements and Coat Colour 125 5.3.2.1 Body measurements 125 5.3.2.2 Coat colour and characteristics 130 5.4 DISCUSSION 132 5.4.1 Anaesthesia 132 5.4.2 Morphometries 133 5.4.2.1 Weight 133 5.4.2.2 Body measurements 134 5.4.3 Coat Colour and Characteristics 136 5.5 CONCLUSIONS 139 CHAPTER6 POPULATION DYNAMICS 141 6.1 INTRODUCTION 141 6.2 METHODS 141 6.2.1 Age Classes and Sex Ratios 142 6.2.2 Breeding Periods and Kitten Survival Rates 142 6.2.3 Density and Site Fidelity 143 6.2.4 Movement 144 VII Table of contents 6.2.5 Interactions 144 6.2.6 Relatedness 145 6.2.7 Data Analysis 146 6.3 RESULTS 147 6.3.1