No description available.

M.Sc. / Members of the Suborder Microchiroptera consume large numbers of insects. When large enough numbers of these bats are present in agricultural areas, the need for insecticides can be reduced significantly. The ZZ2 Tomato Farms in Mooketsi and the Secrabje Farm in Waterpoort, in the Limpopo Province were chosen as study sites. Although ZZ2 focuses on the production of tomatoes, both farms produce a variety of vegetables and fruit. These farms were chosen because the management of both have shown a commitment to conservation and attempt to minimise their impact on the environment. Bat species indigenous to the study areas were captured by means of mist nets for identification purposes. Basic morphological data of captured specimens were collected and recorded. Their roosting behaviour and preferences were studied by visiting diurnal roosts in the two study sites. Microclimatic measurements were taken in roosts occupied by Chaerephon pumilus, Mops condylurus and Taedarida aegyptiaca. Microclimatic measurements were also done in bat houses designed for the housing of bats in agricultural areas. Results suggest that other factors, additional to temperature and relative humidity, contribute to the success and probability of bat house occupancy by bats. Existing roosts in man-made structures such as roofs, can successfully be enhanced to stimulate increase in colony size. Bat activities were determined in agricultural areas and adjacent natural habitats by means of recordings of the echolocation calls of the different bat Families. These were compared to the occurrence of nocturnal flying insect orders that were captured in light traps at the same localities. Of the bat species studied, a positive correlation between increased bat activity and higher number of insects, including pest species, was found. It seems as if the Molossidae has the greatest potential to be utilised in the control of insect pests of agricultural areas in the Limpopo of the bat species studied. A holistic approach favouring insectivorous bats on farms is recommended. This can be done i.a. through the conservation of abundant areas of natural vegetation adjacent to the agricultural areas which would provide foraging for bats during winter, periods of drought or when the lands lie fallow. The excessive and injudicious use of insecticides, which has a negative effect on bats, counteracts the beneficial and cheap alternative of natural insect pest control provided by insectivorous bats.

No description available.

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.