Continued use of artificial roosts by the Eastern Horseshoe Bat Rhinolophus megaphyllus Grey, 1834 (Chiroptera: Rhinolophidae) in Brisbane Forest Park, south-east Queensland

Abandoned mines and other artificial roosts in Brisbane Forest Park ('BFP') were investigated between 2007-2009 and 2021-2023 to determine their potential as microbat roosts, particularly relating to the Eastern Horseshoe Bat Rhinolophus megaphyllus. Thirteen structures were identified as diurnal roosting sites used by R. megaphyllus, with the Little Bent-wing Bat Miniopterus australis and the Large Bent-wing Bat Miniopterus orianae oceanensis also found in one adit. Data derived from diurnal counts of roosting bats are presented here, as well as data on the depth and/or microclimate of structures. Specifically, adits were between 6 and 60 m in total depth with bats generally occupying the darkest portions. The maximum colony size noted during diurnal counts was 45 bats. A tunnel was also investigated for use by microbats in 2021-2023, with 89 R. megaphyllus counted during emergence. No maternity roosts were detected, although mating was observed incidentally in one adit in June. Trapping in late December in the two largest structures only recorded male R. megaphyllus, with one post-lactating and one juvenile female captured in January. The Brisbane area is generally devoid of cave-forming geology, so the population of R. megaphyllus in BFP is considered to be strongly dependent on these artificial underground features.