ABSTRACT The current study documents the findings from immunohistochemical examination of the brains of microbats and megabats (Chiroptera) using antibodies for cholineacetyltransferase (cholinergic neurons), tyrosine hydroxylase (dopaminergic, adrenergic and noradrenergic neurons), and serotonin (serotonergic neurons). The objective of the study was firstly to describe the anatomical organization and morphology of the neuromodulatory systems (nuclear complement) in both microbats and megabats, as there is no literature on these systems in the brains of chiropterans. Secondly, we aimed to investigate whether or not there are differences in these systems between the two suborders of chiroptera in hopes to shed some light on the phylogeny of the two, which is a controversial subject. The two groups were found to possess clear differences in their respective neuromodulatory nuclear complements. The differences observed between the two groups include a dorsal division of the locus coeruleus (A6d), which was absent in microbats but present in megabats, also the absence of an A4 in microbats but clear presence in megabats, and the parabigeminal (PBg) nucleus that was absent in microbats but clearly visible in megabats. The microbats were found to possess a complement that appeared similar to that of insectivores; whereas megabats had a complement resembling that of primates, carnivores and rodents. The differences found between the two groups suggest a diphyletic origin for the two groups.

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Day-roosts are an essential resource for tree-hole roosting microbats (Microchiroptera), providing shelter, protection from predators and an appropriate microclimate for energy conservation and reproduction. Microbats often make use of multiple roosting sites, shifting between roosts frequently. Conservation of tree-hole roosting microbats requires an understanding of roost selection and fidelity to enable the protection of sufficient suitable roosting sites. In Australia, as in other countries, habitat loss, particularly in the form of large hollow-bearing trees, is threatening the survival of microbat populations. In addition, the renewal of natural roosts in Australia is very slow, as trees may need to be 100 years old for hollows to form. Where roosting resources are limited, such as in urbanised areas, batboxes may be used as a substitute. As bat-boxes are also accessible to researchers, these roosting sites can help to improve our understanding of roosting behaviour. / This thesis investigates the roosting behaviour of two sympatric microbat species: Gould’s wattled bat (Chalinolobus gouldii) and the white-striped freetail bat (Tadarida australis). These are insectivorous tree-hole roosting species, which naturally occur in urban Melbourne, Australia. Both species make use of bat-boxes at three sites in Melbourne, often sharing roosts with members of the other species. This provided an opportunity not only to study their use of bat-boxes for conservation management purposes, but to investigate factors influencing bat roost selection and fidelity. This study incorporated PIT tags (microchips) and a detector array at the bat-boxes, in addition to monthly manual bat-box inspections, as a method for monitoring roost-use. This approach enabled the collection of long-term, fine-scale roosting data. These data, along with captive and field-based experiments were used to examine the influence of parasites, microclimate and social structure on roost selection patterns and roost fidelity. The specific questions posed were whether tree-hole roosting bats: select roosts based on physical characteristics; perceive a cost of carrying ectoparasites and avoid infested roosts; select roosts to maintain social associations; and select for specific beneficial microclimates. / The patterns of roost selection, ectoparasite diversity, social structure, and the selection of roost microclimate differed between the two species. Microclimate of the bat-boxes was a strong influence on roost selection for both species, as it is for microbats generally. White-striped freetail bats preferred warmer roosts with stable humidity. For Gould’s wattled bats, the selection of roost microclimate differed between the sexes and even between separate, but adjacent, roosting groups. Patterns of preference indicated that individuals had knowledge of the available roosting sites. / The presence of parasites had no obvious influence on roost selection patterns in either species. The white-striped freetail bat was found to support lower ectoparasite diversity, which may be influenced by characteristics of the pelage and may partially explain why parasite load was not a useful predictor of roost selection in this species. In contrast, Gould’s wattled bat supported a larger diversity of ectoparasites, which showed clear patterns of distribution through the bat populations, and intra-specific and spatial variability. A radio-tracking study indicated that parasites in the roost and on the Gould’s wattled bat may influence their roosting behaviour. Additionally, experimental assessments of the bats’ grooming response to parasites indicated that the perceived costs of these parasites differed with parasites that remained permanently attached to the host eliciting a stronger response than those also found in the roost. The defensive mechanism against parasites that completed part of their life-cycle in the roost was expected to be avoidance behaviour, yet, in both captive and field experiments, these parasites did not strongly influence roost selection or fidelity. / Social associations among white-striped freetail bats appeared to be random, and did not explain roosting patterns. This may reflect the restricted sampling of roosting sites, and the possible role of the bat-boxes in this study as ‘satellite’ roosts, separate from a larger communal roost, likely to be in a large tree-hollow. Unlike white-striped freetail bats, Gould’s wattled bats showed fission-fusion social structure, driven by stronger female associations. The distribution and abundance of parasites was correlated with the social structuring of the host species, and host selection appeared to facilitate transmission. These patterns suggest that female Gould’s wattled bats, in particular, are choosing roosts based on the benefits of social association despite the cost of increased parasite risk, and may provide an explanation for sexual segregation in temperate tree-roosting bats. / This study demonstrates the species-specificity of roosting behaviour, and the importance of investigating several factors that influence roost selection, to better understand roost requirements. It also highlights the inherent complexity in roost selection by tree-hole roosting microbats, which may be making trade-offs between the benefits of social associations and the cost of parasitism, as well as choosing an optimal microclimate. Further investigation into interactions between these factors will greatly advance our understanding of roost selection and fidelity in tree-hole roosting bats.