Population Dynamics of the Critically Endangered, Southern Bent-Winged Bat Miniopterus Orianae Bassanii
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Population Dynamics of the Critically Endangered, Southern Bent-winged Bat Miniopterus orianae bassanii Emmi van Harten B.A. (Natural Resources Education). (Hons). Grad. Cert. Prof. Writing ORCID identifier 0000-0003-4672-754X Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy December 2020 Department of Ecology, Environment and Evolution School of Life Sciences College of Science, Health & Engineering La Trobe University, Victoria, Australia Table of contents Abstract ........................................................................................................................ iv Statement of authorship .............................................................................................. v Preface .......................................................................................................................... vi Acknowledgements .................................................................................................. viii Chapter 1. Introduction ............................................................................................. 11 Context ..................................................................................................................... 12 The southern bent-winged bat Miniopterus orianae bassanii ................................. 17 Study aims and objectives ........................................................................................ 26 Thesis outline ........................................................................................................... 26 References ................................................................................................................ 28 Chapter 2. Cave-dwelling bats in Australia: ecology and conservation ............... 37 Early understanding of Australian cave bats ........................................................... 43 Maternity caves and roosting requirements ............................................................. 46 Winter behaviour of cave-dwelling bats in Australia .............................................. 50 Research methods for studying cave-dwelling bats ................................................. 52 Conservation of cave-dwelling bats ......................................................................... 54 Acknowledgements .................................................................................................. 59 References ................................................................................................................ 59 Chapter 3. High detectability with low impact: optimizing large PIT tracking systems for cave-dwelling bats .................................................................................. 69 Abstract .................................................................................................................... 70 Introduction .............................................................................................................. 71 Methods .................................................................................................................... 74 Results ...................................................................................................................... 82 Discussion ................................................................................................................ 89 Acknowledgements .................................................................................................. 93 References ................................................................................................................ 94 Appendix 1 ............................................................................................................... 99 Chapter 4. Recovery of southern bent-winged bats (Miniopterus orianae bassanii) after PIT-tagging and the use of surgical adhesive ............................................... 101 Abstract .................................................................................................................. 102 Introduction ............................................................................................................ 102 Method ................................................................................................................... 104 Results .................................................................................................................... 105 ii Discussion .............................................................................................................. 108 Acknowledgments .................................................................................................. 109 References .............................................................................................................. 110 Chapter 5. Low apparent breeding-season survival in a critically endangered bat: survival analysis using large-scale passive detection .................................... 113 Abstract .................................................................................................................. 114 Introduction ............................................................................................................ 115 Materials and methods ........................................................................................... 118 Results .................................................................................................................... 121 Discussion .............................................................................................................. 127 Conclusion ............................................................................................................. 134 References .............................................................................................................. 134 Supplementary material ......................................................................................... 142 Chapter 6. Seasonal population dynamics and movement patterns of a critically endangered, cave-dwelling bat ................................................................................ 144 Abstract .................................................................................................................. 145 Introduction ............................................................................................................ 146 Methods .................................................................................................................. 150 Results .................................................................................................................... 153 Discussion .............................................................................................................. 162 References .............................................................................................................. 168 Supplementary material ......................................................................................... 175 Chapter 7. General discussion ................................................................................ 177 Thesis overview ..................................................................................................... 178 Recommendations: conservation actions and research priorities .......................... 187 References .............................................................................................................. 193 iii Abstract Bats comprise a significant component of global biodiversity and contribute to a range of ecosystem services; but, more than half of the world’s bat species assessed for conservation status have declining or unknown population trends. In this study, I investigated the population dynamics of the critically endangered, southern bent- winged bat Miniopterus orianae bassanii, a cave-dwelling taxon in south-eastern Australia. The southern bent-winged bat has experienced severe historical population decline but the current population trajectory is uncertain. Over three years, I tagged 2966 southern bent-winged bats with passive integrated transponder (PIT) tags. Large antennas were used to create vertical detection planes exceeding 8 m2 to detect PIT- tagged bats in flight at a major maternity cave and a non-breeding cave in south-east South Australia. Fifty-two bats recaptured after PIT-tagging had their physical condition reassessed. PIT-tagging procedures were not associated with lowered body mass, infection, or irritation. Subsequent detection rates of the free-flying bats were high, with 97% of PIT-tagged individuals being detected, resulting in over 1.4 million unique detections. Apparent seasonal survival rates were lowest in summer and autumn, particularly for juveniles and lactating females. Lowest survival during the study coincided with severe drought conditions in early 2016. Bats congregated at the maternity cave for most of the year, although there were different movement and migration patterns among sex and age classes, including a previously undescribed migration event occurring over March each year. Overall, the population was more mobile than expected, with bats flying the 72 km between the two roosting caves in just a few hours. Population modelling predicts continued population decline. This study demonstrates that large PIT antennas can be used to safely and successfully detect small volant species, extending the scope for use of PIT-tag technology in wildlife research. Critically,