A Test of the Hutchinson Theory of Interspecific Competition Richard John William Bosworth B.Env.Sc. Honours (The University of Adelaide) Submitted for the Degree of Doctor of Philosophy In the School of Animal and Veterinary Sciences, Faculty of Sciences, University of Adelaide January 2012 Table of Contents A Test of the Hutchinson Theory of Interspecific Competition ........................................... i Table of Contents ................................................................................................................. ii List of Tables ...................................................................................................................... vi List of Figures ................................................................................................................... viii Abstract .............................................................................................................................. xx Declaration ...................................................................................................................... xxiv Acknowledgements .......................................................................................................... xxv Chapter 1 General Introduction ........................................................................................... 1 1.1 Introduction ........................................................................................................... 1 1.1.1 Project Aims ................................................................................................... 6 Chapter 2 Literature Review ................................................................................................ 7 2.1 Introduction ........................................................................................................... 7 2.2 Competition ........................................................................................................... 8 2.2.1 General Competition ...................................................................................... 8 2.2.2 Intra and Interspecific Competition ............................................................... 9 2.2.3 Resource partitioning ................................................................................... 11 2.2.4 Dietary overlap ............................................................................................. 12 2.2.5 Metabolic rate .............................................................................................. 14 2.2.6 Summary ...................................................................................................... 15 2.3 Hutchinson Theory .............................................................................................. 16 2.3.1 Background .................................................................................................. 16 2.3.2 Scientific Debate .......................................................................................... 16 2.3.3 Competition Models ..................................................................................... 18 2.3.4 Alternative explanations .............................................................................. 19 2.3.5 Summary ...................................................................................................... 20 2.4 Agricultural expansion ........................................................................................ 21 2.4.1 Agricultural expansion in Australia and on Kangaroo Island ...................... 21 2.4.2 Herbivore impact in Australia and Kangaroo Island ................................... 22 2.4.3 Summary ...................................................................................................... 24 2.5 Species of Interest ............................................................................................... 24 2.5.1 Tammar Wallaby (Macropus eugenii Desmarest) ....................................... 24 2.5.1.1 Description ............................................................................................ 25 2.5.1.2 Diet, Habitat description and Distribution ............................................ 26 2.5.2 Western Grey Kangaroo (Macropus fuliginosus Desmarest, 1817) ............ 26 2.5.2.1 Description ............................................................................................ 26 2.5.2.2 Diet, Habitat description and Distribution ............................................ 27 ii 2.5.3 Sheep (Ovis aries) ........................................................................................ 28 2.5.3.1 Description ............................................................................................ 28 2.5.3.2 Diet, Habitat description and Distribution ............................................ 29 2.5.4 Goats (Capra hircus) ................................................................................... 30 2.5.4.1 Description ............................................................................................ 31 2.5.4.2 Diet, Habitat description and Distribution ............................................ 31 2.5.5 Summary ...................................................................................................... 32 2.6 Carrying Capacity ............................................................................................... 33 2.6.1 Variation in DSE units ................................................................................. 33 2.6.1.1 Domestic ............................................................................................... 33 2.6.1.2 Wildlife ................................................................................................. 34 2.6.2 Summary ...................................................................................................... 34 2.7 Condition Score ................................................................................................... 34 2.7.1 Domestic ...................................................................................................... 34 2.7.2 Wildlife ........................................................................................................ 35 2.7.3 Summary ...................................................................................................... 36 2.8 Capture Techniques for Macropod species ......................................................... 36 2.8.1 Non Drug Capture ........................................................................................ 36 2.8.2 Drug Capture ................................................................................................ 37 2.8.3 Summary ...................................................................................................... 40 Chapter 3 Processing Experimental Animals .................................................................... 41 3.1 Assessment of Body condition ............................................................................ 41 3.2 Source of experimental animals .......................................................................... 42 3.3 Transporting of experimental animals ................................................................. 43 3.4 Sedation of Kangaroos ........................................................................................ 44 Chapter 4 Pasture Assessment on Kangaroo Island ........................................................... 47 4.1 Introduction ......................................................................................................... 47 4.2 Methods ............................................................................................................... 49 4.2.1 Study sites .................................................................................................... 49 4.2.2 Transect specifications ................................................................................. 51 4.2.3 Plant Cover Survey ...................................................................................... 51 4.2.4 Plant Cover Analysis .................................................................................... 52 4.2.5 Rainfall and Temperature ............................................................................ 52 4.3 Results ................................................................................................................. 52 4.3.1 Rainfall and Temperature ............................................................................ 52 4.3.2 Pasture Comparison at three sites ................................................................ 54 4.3.2.1 Spring 2006 ........................................................................................... 55 4.3.2.2 Summer 2007 ........................................................................................ 57 4.3.2.3 Autumn 2007 ........................................................................................ 59 iii 4.3.2.4 Spring 2007 ........................................................................................... 61 4.3.3 Pasture Comparison on both sides of a boundary fence .............................. 63 4.3.3.1 Chris’s paddock .................................................................................... 63 4.3.3.2 High Paddock ....................................................................................... 64 4.4 Discussion ..........................................................................................................