Date of Award


Degree Type


Degree Name

Doctor of Philosophy




Dr. Brock Fenton

Second Advisor

Dr. Bryan Neff

Third Advisor

Dr. Paul Handford


Group living is widespread among animals. Theory predicts that animals should aggregate if the benefits associated with group living outweigh the costs. Benefits associated with group living could arise passively (e.g. aggregate independently to exploit a patchily distributed resource) or actively (e.g. cooperation). Some forest-dwelling bat species switch roosts frequently, but maintain an association among specific individuals, and therefore are fission-fusion societies, the temporary splitting of colonies into several subgroups. Normally, movements between alternative roosts are costly. Fission-fusion societies might overcome the costs by providing benefits associated with large subgroup size or cooperation. In addition, sociality could influence the movements of individuals within and between social groups and affect the gene flow. However, our understanding about the underlying causes and effects of fission-fusion behaviour is still lacking. I used both direct behavioural observation and indirect molecular analysis to study the roosting behaviour and sociality of Aiyotis formosus. In my study area, M. formosus used two different types of day roosts in summer, houses and foliage, which were extremely different in availability, permanency, and space. I found the roost type affected roosting behaviour of bats. In general, roost switching frequency of foliage- roosting Myotis formosus was high and associated with intrinsic and environmental factors. Myotis formosus in large subgroups switched roosts less frequently than those living in smaller subgroups. Bats were faithful to specific roosting areas, and the nonrandom association between individuals indicated that they live in a fission-fusion society and switched roosts to enhance social interaction. Reproductive status also in affected the association pattern and roost switching frequency of foliage-roosting M formosus while the similarity in genetic relatedness or matrilineal relationship did not facilitate association between individuals. Benefits associated with cooperation or clustering as well as female philopatry are possible reasons for the fission-fusion society of M. formosus. The molecular data based on the contrasted pattern found from the biparentally inherited nuclear microsatellite markers and maternally inherited mitochondrial DNA markers also suggest that gene flow between colonies is male- mediated, while females appeared to show high fidelity to a small roosting area. Behaviourally, the male-mediated gene flow among bat colonies might occur by male dispersal and/or mating outside the colony, including swarming sites, hibemacula, or on the migration route. However, the details about the mating of this species are still unknown.



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