Frogs about town: Aspects of the ecology and conservation of frogs in urban habitats of South Africa DJD Kruger 20428405 Thesis submitted for the degree Philosophiae Doctor in Zoology at the Potchefstroom Campus of the North-West University Supervisor: Prof LH du Preez Co-supervisor: Prof C Weldon September 2014 i In loving memory of my grandmother, Kitty Lombaard (1934/07/09 – 2012/05/18), who has made an invaluable difference in all aspects of my life. ii Acknowledgements A project with a time scale and magnitude this large leaves one indebted by numerous people that contributed to the end result of this study. I would like to thank the following people for their invaluable contributions over the past three years, in no particular order: To my supervisor, Prof. Louis du Preez I am indebted, not only for the help, guidance and support he has provided throughout this study, but also for his mentorship and example he set in all aspects of life. I also appreciate the help of my co-supervisor, Prof. Ché Weldon, for the numerous contributions, constructive comments and hours spent on proofreading. I owe thanks to all contributors for proofreading and language editing and thereby correcting my “boerseun” English grammar but also providing me with professional guidance. Prof. Louis du Preez, Prof. Ché Weldon, Dr. Andrew Hamer, Dr. Kirsten Parris, Prof. John Malone and Dr. Jeanne Tarrant are all dearly thanked for invaluable comments on earlier drafts of parts/the entirety of this thesis. For statistical contributions I am especially also grateful to Dr. Andrew Hamer for help with Bayesian analysis and to the North-West Statistical Services consultant, Dr. Suria Ellis for help and advice on some statistical components of this study. Peter Narins is dearly thanked for expert insight provided in comments about bioacoustic components. I am also especially grateful to Dr. Andrew Hamer whom has given me expert advice on the interpretation of anuran community structure. My fieldwork would have been lonely and lack the excitement if it were not for colleagues and friends whom assisted me and provided jokes for the tedious hours on the road. Petri Bronkhorst, Edward Netherlands, Leon Meyer, Dr. Jeanne Tarrant, Amy Harvey, Lize Steyn, Joanita Viviers, Danél Benadé and Prof. Louis du Preez are thanked for accompanying me to my various research sites. I sincerely thank Marius and Belinda Burger whom have welcomed me into their home and provided accommodation for two weeks. My trips to Cape Town would not be as successful if it were not for Dr. John Measey and volunteers that helped me to identify sites for the study on the Western Leopard Toad. Alison Faraday and her hard-working volunteer team, ToadNUTS, were of much help with the data acquisition of the drift fence study. Mark Day and Hanniki Pieterse also helped to identify breeding sites of Western Leopard Toads. iii No can one achieve any high goals without the help of family and friends. I am grateful to my fiancé, Danél Benadé, for her motivation and patience, including the many snacks and dishes that fuelled my mind, especially in the final months of this thesis. I am also very thankful for the support my parents, Pierre and Madelein Kruger, had provided me in all aspects of life during the past three years, but also recalling my thankfulness for the previous five years that served as a stepping stone to this thesis. I am grateful towards all my friends’ support, motivation and encouragement, including Philip and Elaine Ayres, Leon and Lourinda Meyer, Richard and Carolé Sutherland, Trevor Hallatt, Richard Nortjé, Eybert Tromp, Dr. Mathieu Badets, Dr. Jeanne Tarrant, Ronette Zaaiman and Natasha Viljoen. For my landlady, Hendrine Krieg, I appreciate all the little treats left on my front door. This study was financially supported by Stiftung Artenschutz and the National Research Foundation. Selected accommodation, transport and sound equipment were funded by Stiftung Artenschutz for the bioacoustic study on the Pickersgill’s Reed Frog. This has contributed enormously to the quality of my data. The National Research Foundation, the North-West University as well as the financial director of the Unit for Environmental Sciences and Management, Prof. Nico Smit, are thanked for the scholarships that sustained me for the past three years of this study. Finally, to our Creator, who blessed us with a beautiful world - thank you God for Your care, protection, providence and unconditional love towards all of us. Psalm 23. iv Thesis summary Globally urbanisation impacts on 88% of amphibian species and is recognised as a major cause for the observed amphibian declines. This is as result of habitat fragmentation, alteration in habitat morphology and degradation of habitat quality. The interference of anthropogenic noise on anuran communication and the impacts thereof on their breeding success has become a major research focus in recent conservation studies. However, within the African continent very little research has been conducted on the effects of urbanisation on anuran habitat and the acoustic environment, which is the main focus of this study. The thesis is structured as follows: CHAPTER ONE provides an introduction to the field of urban ecology and relates it to amphibian conservation. The chapter reviews the far reaching and diverse effects of urbanisation on frog populations reported in literature across the world and also supply a broad introduction to the succeeding chapters. It also briefly summarises evidence from literature on the positive contributions brought about by the developed world. Following the vast negative impacts of urbanisation, the importance of amphibians is briefly discussed to motivate their conservation in urban environments, before concluding with a motivation for the need for urban ecological research on amphibians in South Africa. CHAPTER TWO addresses the distribution of amphibian communities across an urban-rural gradient in the city of Potchefstroom and assesses the habitat determinants explaining distribution at both local (pond) and landscape scales. Four surveys conducted spanned the breeding seasons of all species occurring in this region and included three different sampling techniques to detect fish and anuran larvae species. Seven micro-habitat and seven landscape variables were included to evaluate determinants of habitat use among local species and species richness. Using Bayesian modelling, aquatic vegetation, predatory fish and pond size was found to be major determinants shaping species richness on a local scale, whereas surface area of urban central business district had only a slightly negative correlation with species richness on a landscape scale. This is a pioneer study for documenting effects of urbanisation on amphibian communities along an urban-rural gradient in Africa. CHAPTER THREE evaluates the extent of the influence of aircraft acoustic noise on the calling behaviour of the critically endangered Pickersgill’s Reed Frog, Hyperolius pickersgilli. Literature documenting the effects of airplane noise on anuran calling activity is very limited and this study aimed not only to contribute to existing knowledge, but also to provide the first study of its kind within South Africa. Effects on five call properties of H. pickersgilli were determined v using passive and directional recording equipment at two sites, reflecting presence and absence of aircraft flybys. Results showed an increase in calling rate of H. pickersgilli during aircraft flybys. Hyperolius pickersgilli was found to call throughout the night until just before sunrise. The calling behaviour, frequency structure and call sound pressure level of H. pickersgilli suggest that this species is prone to be effected by continuous anthropogenic noise. However, the lack of flights between midnight and sunrise provides a period of no disturbance for the frogs. Future studies on the effects of change in calling behaviour should be supported by playback studies at quiet sites and connected to breeding success to determine if these effects are detrimental to the survival of this critically endangered species. CHAPTER FOUR focussed on the Western Leopard Toad, Amietophrynus pantherinus and was divided into two major parts. One component focussed on the migration of this species across roads and aimed to firstly quantify the number of individuals migrating over a 500 m stretch of road using a drift fence system operated by public volunteers. The drift fence proved very successful, with no roadkill observed during the time it was in place. This study also stressed that large numbers of toads (average of 20.47% of 2 384 toads over six breeding seasons) are still being killed on the urban and suburban roads. Road patrol statistics collected by volunteers are biased in the sense that it is prone to human error, but when a drift fence is constructed, bias is excluded and space for human error limited. The study also provided road sensitivity areas analysed using geographic information systems to create digital buffer zones of 250 m, 500 m and 1 000 m around selected breeding sites. Secondly the study aimed to evaluate the use of data collected by these citizens occupying a volunteering role in the toad’s conservation. The second part of this study was directed towards the acoustic analysis of the call of A. pantherinus. The two main objectives of this component were to 1) evaluate the extent of variation of the call properties in order to 2) assess whether the ambient anthropogenic noise have an effect on these properties. Seven call properties for advertisement calls and four for release calls were analysed. Call properties were found to vary significantly between populations (P<0.05). Although sound pressure level was found to have an effect on variation by using canonical redundancy analysis, variation can also be explained by the geographical isolation of the populations. CHAPTER FIVE provided novel data on the extensive repertoire of Amietia quecketti in terms of its unique calling behaviour.