Roost habitat evaluation and distribution of bats (Chiroptera) in the Durban Metropolitan Region

Based on data collected between 1994 and 1998 by a number of volunteers, distribution patterns and roost habitat preferences within the Durban Metropolitan Region (DMR) were investigated for 16 species of bats for which one or more roosts were visited during the study. Notwithstanding sampling biases, house roosts (’anthrophilic’) were most commonly recorded, followed by tree roosts (’phytophilic’) and underground cave-like roosts (’lithophilic’). Estimates of roost entrance height, facing direction and colony size varied widely within and between species. Species distribution patterns of roosts within the DMR were compared with individual specimen records of bats collected during a rabies scare in 1980/1981. The highest density of roosts was recorded in the Berea suburb close to the city centre, on the slopes of a prominent ridge featuring a number of older double-storey houses (suitable for house-roosting species) and tall exotic trees (suitable for tree-roosting species). The six species which were most frequently recorded in roosts visited in residential areas of Durban were: Epomophorus wahlbergi (29 roosts), Taphozous mauritianus (28 roosts), Chaerephon pumila (26 roosts), Otomops martiensseni (24 roosts), Scotophilus dinganii (14 roosts), and Tadarida aegyptiaca (five roosts). Analysis of spatial aggregation of roosts for five species revealed clumped patterns in four cases, and a random distribution in the fifth. Observed differences in distribution patterns between species could be explained by sampling biases, inter-specific competition, differing habitat requirements, and differing abilities of different species and families of bats to withstand colder temperatures by means of hibernation and torpor.