The Influences of Prey, Predators and Habitat Variables on Drought-Affected Forest Preference in a Darling Range Endemic Skink
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The influences of prey, predators and habitat variables on drought-affected forest preference in a Darling Range endemic skink Sean Andrew Smithies, BSc This thesis is presented for the degree of Bachelor of Science in Conservation and Wildlife Biology with Honours June 2016 School of Veterinary and Life Sciences Murdoch University i Declaration I declare that this thesis is my own account of my research or is appropriately acknowledged, and contains as its main content work, which has not been previously submitted for a degree at any tertiary educational institution Sean Andrew Smithies Date: 06/06/2016 ii Abstract Large-scale canopy collapse occurred within the northern jarrah (Eucalyptus marginata) forest of southwest WA following a record hot and dry year/summer in 2010/11. The forest die-off had noted effects on the reptile communities. The endemic lizard Ctenotus delli (Scincidae) was recorded more frequently within drought-affected sites compared with adjacent apparently healthy intact regions. The present study investigated possible drivers for this apparent preference, quantifying: 1) leaf litter invertebrate assemblages and termite activity (prey influence); 2) predatory bird assemblages (predator influence); and 3) the effect of black and white disruptive markings on concealment of skinks in leaf litter (primary antipredatory response) between drought-affected and healthy sites. Leaf litter invertebrate assemblages did not differ across drought-affected and healthy sites, however, predatory bird assemblages varied significantly between drought-affected and healthy sites (P = 0.009) with greater numbers of predatory birds observed within healthy sites. Plasticine models of three variations (side-striped, back- striped, and plain) placed among various leaf litter densities revealed that side-striped models were attacked less severely (P =0.039) than back-striped models, although there were no differences in the total numbers of attacks recorded. Therefore, side-stripes (as found on C. delli) did not minimise detection but may increase survivorship. Further implementation of invertebrate trapping coupled with behavioural studies in avian predators across drought-affected and healthy sites may conclusively determine the selective pressures behind drought-affected site preferences of C. delli. iii Acknowledgements I would like to acknowledge and thank my supervisors, family and friends for their contributions and support given throughout the course of the past year. A massive thank you extends out to my supervisors Associate Professor Trish Fleming, Dr Bill Bateman, Professor Giles Hardy and Dr Shannon Dundas for their advice and guidance given throughout the year. I am extremely grateful for all the time and interest that was invested in the project and all the assistance given in planning, the field, with statistics and writing. The constant support and reassurance provided by my supervisors throughout the year, especially when stress levels ran high, was greatly appreciated. Special acknowledgements extend out to: Dr Katinka Ruthrof and Emma Steel for showing me around the field sites. Josh Collard for assisting me in the field on multiple occasions, whether it be setting up or retrieving models or cameras, burying toilet rolls or collecting leaf litter. All my field assistants: Josh Collard, Hannah Ashbil, Michael Childs, Nicki Miglori, and Jack Banister. Everyone in “The Dungeon” and “Bat cave” for the constant support and for making such a friendly, positive workspace. Special thanks extend to Narelle, Nicki and Meg. Lastly, I would like to thanks my family and partner for their support. To Dr Lynne and Dr Hugh Smithies for all your assistance in the field, general feedback and support throughout the year. To Hannah Ashbil for your assistance in the moulding and painting of the plasticine models and help out in the field. Thank you all for being there for me iv throughout the year no matter what, and your constant support, especially during the most stressful times. Murdoch University approval for this study was attained from the fieldwork safety plan and Risk Assessment Murdoch Project (RAMP) form (RAMP0321). It was also approved by the Murdoch University ethics committee (RW2769/15). The Department of Agriculture and Food (DAFWA) were provided with a Notification Form – Licence to use animals for scientific purposes, scientific number (U6 2014-2016), scientific establishment name (Murdoch University). v Table of Contents Declaration ........................................................................................................................ ii Abstract ............................................................................................................................ iii Acknowledgements .......................................................................................................... iv Table of Contents ............................................................................................................. vi List of Tables.................................................................................................................. viii List of Figures .................................................................................................................. ix Glossary ........................................................................................................................... xi 1 General Introduction ................................................................................................ 1 1.1 Physiography, vegetation and climate ....................................................... 2 1.1.1 The southwest region of Western Australia .............................................. 2 1.1.2 The drought ............................................................................................... 5 1.2 Lizards of the northern jarrah forest and the study species: Ctenotus delli 7 1.3 Project Aims .............................................................................................. 9 2 Does drought influence the leaf litter invertebrate communities? ......................... 12 2.1 Introduction ............................................................................................. 12 2.2 Methods ................................................................................................... 14 2.2.1 Site selection ............................................................................................ 14 2.2.2 Leaf litter availability .............................................................................. 16 2.2.3 Leaf litter invertebrate surveys ................................................................ 16 2.2.4 Termite activity index.............................................................................. 17 2.2.5 Data analyses ........................................................................................... 18 2.3 Results ..................................................................................................... 19 2.4 Discussion................................................................................................ 23 2.4.1 Limitations of this study .......................................................................... 26 2.4.2 Conclusions ............................................................................................. 26 3 Does drought influence predatory bird communities?........................................... 28 3.1 Introduction ............................................................................................. 28 3.2 Methods ................................................................................................... 31 3.2.1 Bird surveys ............................................................................................. 31 3.2.2 Data analyses ........................................................................................... 32 3.3 Results ..................................................................................................... 32 3.4 Discussion................................................................................................ 41 3.4.1 Limitations of this study .......................................................................... 45 3.4.2 Conclusions ............................................................................................. 46 4 Do body stripes on Ctenotus delli provide camouflage under different leaf litter conditions? .................................................................................................... 47 4.1 Introduction ............................................................................................. 47 4.2 Methods ................................................................................................... 50 4.2.1 Plasticine models ..................................................................................... 51 4.2.2 Camera Traps........................................................................................... 52 4.2.3 Model placement ..................................................................................... 52 4.2.4 Scoring attacks......................................................................................... 53 4.2.5 Statistical analyses ................................................................................... 54 4.3 Results ..................................................................................................... 55 4.3.1 Whether models were attacked or not ....................................................