Trypanosomes are blood-borne parasites that can infect a variety of different vertebrates, including animals and humans. This study aims to broaden scientific knowledge about the presence and biodiversity of trypanosomes in Australian bats. Molecular and morphological analysis was performed on 86 blood samples collected from seven different species of microbats in Western Australia. Phylogenetic analysis on 18S rDNA and glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) sequences identified Trypanosoma dionisii in five different Australian native species of microbats; Chalinolobus gouldii, Chalinolobus morio, Nyctophilus geoffroyi, Nyctophilus major and Scotorepens balstoni. In addition, two novels, genetically distinct T. dionisii genotypes were detected and named T. dionisii genotype Aus 1 and T. dionisii genotype Aus 2. Genotype Aus 2 was the most prevalent and infected 20.9% (18/86) of bats in the present study, while genotype Aus 1 was less prevalent and was identified in 5.8% (5/86) of Australian bats. Morphological analysis was conducted on trypomastigotes identified in blood films, with morphological parameters consistent with trypanosome species in the subgenus Schizotrypanum. This is the first report of T. dionisii in Australia and in Australian native bats, which further contributes to the global distribution of this cosmopolitan bat trypanosome.

Physical characteristics of roost sites used by the lesser long-eared bat Nyctophilus geoffroyi and Gould's wattled bat Chalinolobus gouldii were investigated in a farmland–remnant vegetation mosaic and adjacent forested floodplain in south-eastern Australia. A total of 45 individuals of N. geoffroyi and 27 C. gouldii were fitted with radio-transmitters, resulting in the location of 139 and 89 roosts, respectively. Male N. geoffroyi roosted in trees, fallen and decayed timber and artificial structures. These roosts were low to the ground, mainly under bark and in cracks in timber. Roosts of female N. geoffroyi were located higher above ground, and all within trees. Maternity roosts were predominantly located in large dead trees, approximately twice the diameter of roost trees used by females outside the breeding season. No maternity roosts were found under bark, despite half the roosts used by non-breeding females being located in these situations. Both sexes roosted primarily in dead timber and used cavities where the narrowest dimension of the entrance was 2.5 cm. Most roosts of C. gouldii were in dead spouts on large, live river red gum Eucalyptus camaldulensis trees. Intraspecific differences in roost characteristics were less pronounced for this species. Despite access to the same roosting opportunities, there were marked differences in roost selection between N. geoffroyi and C. gouldii. Both species favoured large diameter trees, but differed significantly for all other measured variables: type of roost structure, condition of roost tree (live or dead), height of roost tree, height of roost, and entrance dimensions. Although these species are among the most widespread bats in Australia and are often considered to be habitat ‘generalists’, both displayed a high level of discrimination in the roosts used. Clearly, roosting requirements are a complex and important issue in the conservation of even the most common species of bats.

Prolonged sperm storage, rare among mammals, is widespread among bats and may promote sperm competition, assuming stored sperm are fertile. However, while sperm storage has been documented in many bat species, there have been few investigations of the fertility of stored sperm. Related to this, and a fundamental question in the study of competition at the gametic level, is the effect of mating order on success during sperm competition. For mammals there are no clear mating order effects, in part because females do not store sperm for prolonged periods, but there have been no investigations of mating order effects during sperm competition in sperm-storing bats. I report here on a study designed to investigate the fertility of stored sperm and the effects of mating order on success during sperm competition in a captive colony of Australian long-eared bats Nyctophilus geoffroyi (Chiroptera: Vespertilionidae). Bats were housed in outdoor flight-cages, under natural light and temperature regimes. Females were housed serially with two males and were separated from them at intervals throughout the year.

Blood plasma progesterone concentrations, measured using double antibody radioimmunoassay, were monitored to assess the duration of sperm storage. Paternity of offspring was assessed using genetic markers identified using gel electrophoresis of blood enzymes. Blood plasma progesterone concentrations were basal from early autumn till mid-late winter, increased markedly during pregnancy, and generally fell back to basal 5–6 weeks post-partum. Data indicated that females could store fertile sperm for more than 90 days, while sperm stored by males were fertile after 4–5 months' storage. Paternity was significantly biased toward one male which fathered all offspring. Results are discussed in the context of sperm competition.