Linking frogs with flow: Amphibian community response to flow and rainfall on a dryland floodplain wetland Joanne Ocock A thesis in fulfilment of the requirements for the degree of Doctor of Philosophy Australian Wetlands, Rivers and Landscapes Centre School of Biological, Earth and Environmental Sciences University of New South Wales, Australia September 2013 …But he’d be sitting by the campfire, trying out a simple conversation, and suddenly people would get upset over nothing at all and drive him off. You didn’t expect people to get nasty just because you’d said something like, ‘My word, when did it last rain here?’ did you? “The Last Continent” by Terry Pratchett i Abstract Floods structure the biota of floodplain wetlands, driving spatial and temporal patterns of vegetation, invertebrates, and waterbirds. Flood pulses trigger ‘booms’ in productivity and biodiversity as aquatic biota respond to abundant freshwater habitat and resources. Water extraction and river regulation have decreased the magnitude, duration and frequency of floods, and reduced floodplain extent. To address this problem, environmental water management aims to restore wetland functioning by mimicking the natural flow regime but this requires knowledge of broad ecological responses and associations to flows. Despite amphibians forming a significant component of wetland foodwebs, their response to river flows is poorly known. My work focused on understanding this response in the Macquarie Marshes, a dryland floodplain wetland in Australia. The Macquarie Marshes are a wetland of international significance, severely affected by river regulation. They currently benefit from significant public environmental water investment initiatives. In this thesis I aimed to: (1) investigate variations in relationships between flooding and responses of amphibian species, and quantify the contribution amphibians make to the flood-pulse derived resource ‘boom’; and (2) assess the threat river regulation poses compared to other known amphibian threats across Australia. In Chapter 1, I overviewed the current status of knowledge of amphibian response to flooding and relationships with flow regimes in floodplains. I then compared the relative influence of weather and inundation on movement and behaviour of two amphibian species, with different life histories (Chapter 2). In Chapter 3, I tested predictions, based on life history characteristics, of species’ flood associations by measuring adult abundance and calling abundance in relation to habitat and flow variables. I then calculated biomass of amphibians across different size floods, and compared the contributions of different flood-association groups (Chapter 4). I also assessed likely frog species at risk of the effects of river regulation across Australia, relative to other threats (Chapter 5), using understanding of the relationships between flooding and life histories of frog species. Finally in Chapter 6, I re-evaluated the threat of altered flow regimes on amphibians and the opportunities to effectively manage this threat for some frog species which respond to flood and inundation patterns. iv Acknowledgements I would like to express my sincere thanks to a number of people, who have been an integral part of my research and writing. Firstly, I would like to thank the landholders and people associated with the Macquarie Marshes, not only for permission to access to the Marshes but imparting a deep love of a most amazing wetland. For your time, patience, support, car-rescues and much more, many thanks to Garry, Leanne, Teague and Jet Hall, Ray and Sue Jones, Simon, Kelly and Lucy Earl, Adam, Leone, Lachlan and Mitchell Coleman, Dave and Leigh Thornton, Doug and Chris Andrews, Peter, Rhonda and Linda McClellan, and Bill Johnson. Additionally I’d like to thank Debbie Love (NSW Office of Environment and Heritage) for her commitment of the well-being of frogs in the Marshes. I would like to acknowledge the financial support of NSW Office of Environment and Heritage, the NSW Frog and Tadpole Study Group, and the Foundation for National Parks and Wildlife Service. My thanks to the large number of dedicated people who gave their time to help with field work in the Marshes, coping with the long hours, late nights, leeches, mozzies, snakes and various catering styles: Andrea Sabella, Lauren Harrison, Rowena Hamer, Marie Attard, Adam Birnbaum, Dickie Tate, Chris Suttie, Carly Humphries, Jonathan Windsor, Lizzy Swanson, Emma McLeod, Claire Laws, Stephan Mahony and Lilly Schwartz. To those who came from outside of Australia to be part of the research family, Ashley Soltysiak, Sarah Meredith, Dave Herasimtschuk, Angela Knerl and Diana Grasso, I am indebted to you, thank you many times over for making the trip. Also, I owe a huge debt of gratitude to my Sydney family, including Celine Steinfeld, Rachel Blakey, Sam Dawson, Sylvia Hay, Leigh Pyman, Ben Harris, Rhiannon Dalrymple, Habacuc Flores-Moreno, Alice Blackwood, Dani Binder, Rowena Hamer, Andrea Sabella, Gilad Bino, and Lucy Nairn. I am also very grateful to colleagues at the Australian Wetlands, River and Landscapes Centre, particularly Sharon Ryall for all kinds of support and Rachael Thomas for all kinds of data. The encouragement and unconditional support of my whanau to follow my dreams and passion, has got me through the tough times – much love and special thanks to Fiona and Ken, Anita and Mike, and Sarah Cragg. Finally, to my supervisors and mentors Richard Kingsford, Trent Penman and Jodi Rowley, you inspire me and I am forever grateful for your time, email replies, patience, v humour and guidance in what has been an extremely rewarding experience. My learning has been immense and I will always be proud of having you on my PhD journey. Your commitment to me and my research was inspiring and also your commitment to the well-being of the Australian wetlands and frogs. Also, a tip of the hat to the rain-gods for providing me with the best conditions for a frog PhD in inland New South Wales for a decade. vi Preface This thesis consists of six chapters and one appendix. Chapters two to five are self- contained and have been submitted or are in preparation for a journal article. Some repetition subsequently occurs. Appendix Two has been published and is identical to the published version. To prevent unnecessary duplication a single reference list is provided at the end of the thesis. This thesis is a compilation of my own work, with guidance and advice from my supervisors Richard Kingsford, Trent Penman and Jodi Rowley. All chapters were conceptualised either by myself or jointly with my supervisors. I conducted all data analysis, wrote and illustrated the manuscripts. I also generated all maps and photographs included in this thesis. My supervisors proof-read and edited the final manuscript versions. Contributions of co-authors are detailed below: Chapter 2: R. Kingsford, T. Penman and J. Rowley gave conceptual advice and guidance as my supervisors. Submitted for publication in Austral Ecology. Chapter 3: R. Kingsford, T. Penman and J. Rowley gave conceptual advice and guidance as my supervisors. Chapter 4: R. Kingsford, T. Penman and J. Rowley gave conceptual advice and guidance as my supervisors. R. Thomas and S. Ren provided modelling and mapping data. Chapter 5: R. Kingsford, T. Penman and J. Rowley gave conceptual advice and guidance as my supervisors. Appendix Two: Ocock, J.F., Rowley, J.J.L., Penman, T.D., Rayner, T.S., and Kingsford, R.T., 2013. Amphibian Chytrid Prevalence in an Amphibian Community in Arid Australia. EcoHealth 10, 77-81. R. Kingsford, T. Penman and J. Rowley gave conceptual advice and guidance as my supervisors. T. Rayner provided fieldwork and logistical support. vii Contents 1. Frogs, flows and rainfall ................................................................ 1 2. Frogs during the flood: differential behaviours of two amphibian species in a dryland floodplain wetland .......................................... 12 2.1 Abstract ........................................................................................................ 12 2.2 Introduction ............................................................................................... 13 2.3 Methods ....................................................................................................... 15 2.4 Results ......................................................................................................... 23 2.5 Discussion.................................................................................................... 31 3. Implications of habitat and flood associations of frogs in dryland floodplain wetlands in relation to river regulation and management ....................................................................................................... 35 3.1 Abstract ........................................................................................................ 35 3.2 Introduction ............................................................................................... 36 3.3 Methods ....................................................................................................... 39 3.4 Results ......................................................................................................... 43 3.5 Discussion .................................................................................................... 55 4. The biggest losers: frog biomass in regulated river systems ........ 59 4.1 Abstract .......................................................................................................