Alternate Foraging Strategies and Population Structure of Adult Female
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ALTERNATE FORAGING STRATEGIES AND POPULATION STRUCTURE OF ADULT FEMALE AUSTRALIAN SEA LIONS Andrew D. Lowther BSc (Hons) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy University of Adelaide Faculty of Science School of Earth and Environmental Sciences University of Adelaide February 2012 TABLE OF CONTENTS LIST OF TABLES......................................................................................... VI LIST OF FIGURES.......................................................................................VIII DECLARATION OF ORIGINALITY.............................................................. X STATEMENT OF CONTRIBUTION…………………………………………...XI DEDICATION.............................................................................................. XII ACKNOWLEDGEMENTS........................................................................... XIII ABSTRACT................................................................................................. XVI CHAPTER 1. GENERAL INTRODUCTION...............................................................1 IMPORTANCE OF ECOLOGY AND GENETICS IN DEFINING POPULATIONS………………………………………….....................................2 INDIVIDUAL SPECIALISATION IN FORAGING BEHAVIOUR AND POPULATION STRUCTURE..........................................................................4 THE OTARIIDAE…………………………….....................................................6 AUSTRALIAN SEA LIONS…………………….................................................7 NEED FOR RESEARCH………………………………………………………….8 THESIS AIMS.................................................................................................10 CHAPTER 2. DETECTION OF ALTERNATE FORAGING STRATEGIES IN AUSTRALIAN SEA LION (NEOPHOCA CINEREA) BREEDING COLONIES USING STABLE ISOTOPE ANALYSIS................................................................................11 ABSTRACT...............................................................................................................12 INTRODUCTION.......................................................................................................13 MATERIALS AND METHODS...................................................................................17 I Study sites......................................................................................................17 Sampling – Adult Female Australian Sea Lions..............................................17 Sampling – Pups.............................................................................................18 Isotope Analysis..............................................................................................19 Data Analysis..................................................................................................21 RESULTS..................................................................................................................23 Adult Female Foraging Behaviour..................................................................23 Fractionation of Isotopes from Mother to Pup................................................23 Pup Whisker Isotope Ratios and Intracolony Foraging Ecotype Frequencies...................................................................................................25 DISCUSSION...........................................................................................................26 Pups as Surrogate Measures of Maternal Foraging......................................27 Intra-Colony Segregation of Maternal Foraging Behaviour...........................29 Conclusion.....................................................................................................32 CHAPTER 3. CREATURES OF HABIT: FORAGING SITE FIDELITY OF ADULT FEMALE AUSTRALIAN SEA LIONS.......................................................................43 ABSTRACT...............................................................................................................44 INTRODUCTION.......................................................................................................45 MATERIALS AND METHODS...................................................................................49 Study sites and sampling................................................................................49 Data analysis..................................................................................................51 RESULTS..................................................................................................................56 Inshore and offshore foraging ecotype designation........................................56 Stability of foraging behaviour over time.........................................................57 II Movement patterns of individuals...................................................................58 DISCUSSION............................................................................................................59 Individual long-term specialisation in foraging behaviour...............................61 Ecotype-specific differences in movement behaviour and body condition....63 Seasonality of individual foraging behaviour..................................................64 Conclusions....................................................................................................66 CHAPTER 4. POPULATION STRUCTURE OF ADULT FEMALE AUSTRALIAN SEA LIONS DRIVEN BY FINE-SCALE FORAGING SITE FIDELITY......................79 ABSTRACT................................................................................................................80 INTRODUCTION.......................................................................................................81 MATERIALS AND METHODS...................................................................................85 DNA Amplification...........................................................................................86 Stable Isotope Analysis..................................................................................87 Data Analysis..................................................................................................87 RESULTS..................................................................................................................90 Mitochondrial DNA control region diversity....................................................90 Strong genetic partitioning among colonies...................................................91 Alternate foraging behaviours........................................................................91 Environmental determinants of genetic structure and foraging behaviour....92 DISCUSSION............................................................................................................93 Matrilineal population structure is unrelated to broad-scale ecological processes......................................................................................................93 III Is individual niche-width specialisation driving matrilineal population structure ?.....................................................................................................95 Future Directions...........................................................................................98 Conclusions..................................................................................................100 CHAPTER 5. GENERAL DISCUSSION.................................................................111 Defining the degree of habitat specialisations………………………………………..112 Stability of individual foraging specialisation over time………………………………113 Individual specialisation as a mechanism to drive population structure……………115 Do adult female Australian sea lions maintain individual foraging specialisation across generations ?...............................................................................................116 The evolution of a unique life history………………………………………………..…118 Future research and conclusions………………………………………………………123 APPENDIX. MATERNAL STRATEGIES OF THE AUSTRALIAN SEA LION (NEOPHOCA CINEREA) AT DANGEROUS REEF, SOUTH AUSTRALIA...........125 ABSTRACT..............................................................................................................126 INTRODUCTION.....................................................................................................127 MATERIALS AND METHODS.................................................................................130 Maternal attendance, female body condition and milk collection..................131 Milk composition...........................................................................................132 Pup growth...................................................................................................133 Statistical analysis........................................................................................133 RESULTS................................................................................................................135 Maternal attendance.....................................................................................135 IV Milk-lipid content...........................................................................................136 Pup growth....................................................................................................137 Comparison between Seal Bay and Dangerous Reef..................................139 DISCUSSION..........................................................................................................139 Maternal Strategy.........................................................................................139