Intraspecific Variation in the Acoustic Signals of Birds and One Species

lntraspecific Variation in the Acoustic Signals of Birds and One Species of Frog: lmplications for the Acoustic ldentification of lndividuals A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy from the University of Adelaide Daniel Rogers BSc (Hons) lll Acknowledgments A great many people have assisted me along the way to completing this work. I would firstly like to thank my family, and especially my mother and father, for instilling in me the notion that if I was passionate enough, I could achieve anything. The fact that my passion lies in the realm of biological conservation must also be attributed to them, by showing me the wonders of the natural world from a very early age. Thanks, Mum and Dad. I would also like to thank Dr. David Paton, for his enthusiastic supervision of this project. I was approached by David with the idea of doing a PhD on acoustic identification of individual birds. Despite neither of us having any background in bioacoustics, Dave's enthusiasm for the idea has allowed my knowledge in the field to flourish, and helped me to maintain my own enthusiasm for the project. As I was also a true omithological novice at the beginning of this work, David also introduced me to the absolute wonders and spectacle of natural history in South Australia, and it is for this that I am certainly most grateful. 'When you take on David Paton as a supervisor, you also get the lab, and all its members have assisted me in one way or another. Special thanks must be given to Colin Bailey, Emma Crossfield, Brydie Hill and Nigel Willoughby. These people get a special mention for the moral support they provided, and allowing me to maintain (and improve upon) my sense of humour in the face of adversity (they also helped out with field work from time to time, but this was really of secondary importance). More generally, the many students that have passed in and out of the lab during my PhD tenure all provided fantastic support in one way or another, and the comradeship of those in the Paton lab was certainly a special highlight of my degree. With regard to the work on P. bibronii,I am especially grateful to Nicola Mitchell and Oliver Berry.Nicki was the person who originally suggested that P. bibronii might make a good study organism for what I was trying to do, and her company and support during those long, dark winter nights when we were both out chasing frogs made it all worthwhile. Nicki also assisted with the collection of call recordings and other components of my fieldwork, but again, this kind of assistance was of lesser value. As I'm sure a number of students from mine and Nicki's generation would agree, the level of Nicki's academic skills, coupled with her extraordinary effort and perserverence, made her an academic role model for us all. Other grad students who toiled along with me to this point, and provided support when it was most needed, included Ben Smith, Mark Siebentritt, and Sarah Smith. Ben was especially supportive during the write-up phase of my work, as we developed the habit of pushing each other to battle on. Outside of the student body of the department, others who provided assistance included Piers Brissenden, Gail Edwards, Rebecca Dunstan, Phil Kempster, Prof. Russell Baudinette, Assoc Prof. Keith Walker, and many others. These people were invaluable in providing technical and logistic support, as well as academic guidance. Outside of Adelaide University, my work was improved upon greatly through drscussrons with the following people: Dr. Allan Burbridge (Dept. of Conservation and Land Management), Harold Crouch, Dr. Jeremy Robertson (Flinders University), John Seymour, Dr. David Westcott (CRC Tropical Rainforest Ecology), Dr. Barb Wilson (Deakin University). Harold Crouch also provided me with recordings of D. broadbenti to include in my work on geographic song variation in this species. Finally, I would like to thank my wife Trish. Our marriage is roughly as old as this degree, so she has most certainly been here every step of the way, and has experienced this roller-coaster ride in much the same way I have. As with the many other people who helped along the way, I am especially grateful to Trish for the moral and emotional support that she provided, especially when my attitude was less than average during the writing-up phase. This thesis is dedicted to the memory of my grandfather, Jim Hume, who passed away during its creatron. Abstract The ability to identify individual animals within species is now an important tool in ecological research, and can assist in obtaining knowledge regarding the demographics, movement pattems and behavioural ecology of animal populations. Current techniques used to identify individual animals generally require each individual to be captured and artificially marked in some manner. These have the potential to significantly influence the behaviour of target individuals. Such impacts are important, both from the perspective of the welfare of the animals, and for the validity of the data being collected. While the effects of capture and marking can be determined experimentally, non-tnvastve alternatives for identification exist. These alternatives are largely based upon intraspecific variation in some feature. For example, phenotypic variation in some features are often used to discriminate between individuals in a non-invasive manner, such as variation in the patterns of tigers and giraffe. Many species of animal use acoustic cues to discriminate between and recognise conspecific individuals, such as mates, territorial neighbours or kin. Such systems of recognition require that the acoustic signals of such species possess individually-distinct acoustic cues. These cues have been used by a number of investigators to demonstrate the potential for identifying and discriminating between individuals of certain species acoustically. The broad objective of this thesis is to investigate patterns of intraspecific variation in the acoustic signals of a range of vocal animal species, with the ultimate objective of demonstrating vocal individuality in these species, in a manner that allows for the practical identif,rcation of individuals acoustically. The results of vocal individuality presented in this thesis focus on two methods of quantitative song analysis, discriminant function analysis and cross-correlation analysis. The majority of studies to date concerned with the acoustic identification of individuals have presented results using discriminant function analysis, as this multivariate technique is well suited to investigating pattems of variation both within and between individuals. However, the principle disadvantage of discriminant function analysis is its inability to identify new individuals, and therefore its limited application for use in surveys of animal populations. Cross-conelation analysis, however, allows for the comparison of as little as two acoustic recordings, and is therefore potentially more applicable as a survey tool, provided that vocal individuality canbe demonstrated with this method. vl While this thesis aims to demonstrate vocal individuality in a broad range of vocal species, the results focus on two species: Bibron's Toadlet Pseudophryne bibronii and Rufous Bristlebird Dasyornis broadbenti. Pseudophryne bibronii is a small Australian anuran species, in which the male commonly uses two distinct call t1pes. Calls of P. bibronii were collected from 50 different individuals over three breeding seasons. Comprehensive analyses of both call types suggest that, across the three breeding seasons, the calls of P. bibronii varied as much intra-individually as between individuals, largely as a result of intra-individual variation between different nights. Although vocal individuality was demonstrated within the timeframe of single nights, such a system of acoustic identification of individuals does not provide any extra benefit from the current methods used to survey anuran populations. These attempts to demonstrate vocal individuality in P. bibronii are, however, the first for an anuran species, and the potential for vocal individuality still exists in other anurans, such as those for which individual acoustic recognition has been demonstrated. Intraspecific variation in the songs of Dasyornis broadbenti werc analysed across a variety of both temporal and geographic scales. Studies of small focal groups of individuals demonstrated that both males and females possessed repertoires of multiple distinct song types, a proportion of which were common with the song types of their immediate territorial neighbours. The system of acoustic identification of individuals demonstrated for D. broadbenti is based upon this phenomenon of shared song t1pes, with different individuals being compared initially through the analysis and comparison of these shared song types. When the shared songs of different individuals were compared using both discriminant function analysis and cross-correlation analysis, high levels of vocal individuality were demonstrated for the songs of both sexes, amongst the focal group of 12 individual bristlebirds. However, such vocal individuality was not found between syllable types that were classified as belonging to the same type of syllable qualitatively. Vocal individuality in D. broadbenti was therefore limited to the comparison of common song types. Although these common song types were more likely to be encountered between territorial neighbours, common song types were also encountered between individuals

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