An acoustic survey of zoophagic bats on islands in the Kimberley, Western Australia, including data on the echolocation ecology, organisation and habitat relationships of regional communities

Abstract

-Bat ultrasound was recorded on 30 of the in-shore islands along the Northern Kimberley coast as part of a biological survey to assess their conservation potential as microcosms of the region's biodiversity. Species were identifi ed from their search-mode echolocation call sequences using a call library based (mainly) on two variables: the frequency maintained for the greatest number of cycles (F peakC ) and sharpness quotient (Q ). Populations of 20 of the 21 species that comprise the Northern Kimberley region's zoophagic bat fauna are now known to occur on these islands, an average of 8±0.6 (S.E.) species per island.The Kimberley has two compositionally distinct bat communities, one occupying landward environments and the other occupying mangroves. Both were represented on the islands. In each community, the search-mode calls of syntopic species were dispersed in spectral space, with few showing more than peripheral overlap in their spectral variables (Q and F peakC ). Their different call designs were functionally appropriate to differences in (1) foraging niche predicted from empirical data on species' fl ight capabilities and foraging behaviours, and (2) airframe variables related to fl ight performance and control. These observations imply a niche-assembly model of metacommunity structure. Pleistocene climatic fl uctuations and habitat fi ltering also appear to have infl uenced metacommunity structure at regional scales. However, nestedness was observed in assemblage composition that could be explained by environmental factors, implying the infl uence of environmental controls. The richest bat assemblages were recorded on the most mesic of the large inshore islands with cavernous landscapes and permanent pools.Comparison with surrounding regions revealed a diversity-productivity model of faunal structure, with an organisation that conforms to the specialisation hypothesis. Six islands, including their mangrove stands, are identifi ed as priorities for conservation. There are no published assemblage data with which to assess the organisation of bat faunas on Australia's continental islands, despite the importance of these islands as conservation arks (Nias et al. 2010). The Kimberley's inshore islands extend from Sunday Island in King Sound to Adolphus Island in Cambridge Gulf ( Figure 1) and, in terms of their climate, geology and biogeographical history, belong to the Northern Kimberley bioregion (e.g. Gibson and McKenzie 2012). Of the 24 species of echolocating bats listed for the Kimberley, 21 are known from the Northern Kimberley (Burbidge et al. 2008;. Prior to this study, however, available data on the region's island bat faunas was fragmentary, as it was gleaned from opportunistic collections made during a few brief visits over the last 40 years by zoologists carrying out general vertebrate surveys (e.g. McKenzie et al. 1978;Friend et al. 1991;McKenzie et al. 1995;How et al. 2006). The richest list was from Koolan Island, where iron ore has been mined since the 1960s (McKenzie et al. 1995)...

A molecular and morphological investigation of species boundaries and phylogenetic relationships in Australian free-tailed bats Mormopterus (Chiroptera : Molossidae)

“…M. cobourgianus occurs coastally from Exmouth to western Gulf of Carpentaria. However, the Western Australian and Northern Territory populations appear disjunct, with no records yet from the northern and eastern Kimberley coast or islands, despite this area being well surveyed (McKenzie and Bullen 2012). Associated with mangrove communities in Western Australia Bullen 2009, 2012) but also woodland in the Northern Territory (Milne et al 2008).…”

Biogeographic patterns on Kimberley islands, Western Australia

“…The sampling strategy used was specifi c to each of the targeted taxonomic groups and detailed elsewhere (see Doughty et al 2012;Gibson and Köhler 2012;Gibson and McKenzie 2012b;McKenzie and Bullen 2012;Pearson et al 2013;Palmer et al 2013;Lyons et al 2013). We aimed to sample each of the taxonomic groups as systematically as possible within each of the selected habitat types.…”

“…The relatively larger islands such as Augustus, Bigge and Boongaree tended to be the focus of previous surveys, however correlations between island area and survey effort were low to moderate (bats: 0.37; birds: 0.56; reptiles: 0.57; non-volant mammals: 0.62), suggesting a limited bias. The likelihood of false absences and their implications, as well as the adequacy of the sampling more generally, are further discussed in the relevant papers focusing on each taxonomic group (see Doughty et al 2012;Gibson and Köhler 2012;Gibson and McKenzie 2012b;McKenzie and Bullen 2012;Pearson et al 2013;Palmer et al 2013;Lyons et al 2013). While our knowledge on each of the taxonomic groups we sampled on individual islands is likely to be incomplete, the KIBS substantially improved this knowledge, and the analyses revealed strong Results of AIC c -based model selection for the species richness of Northern Kimberley endemic species on the islands sampled during the KIBS (four most supported models shown); also shows maximised loglikelihood function [log(L)], number of model parameters (K), AIC c differences (Δ i ), Akaike weights (w i ) and percent of deviance explained by each model (%Dev).…”

“…In north-western Australia, closed-forest mangrove communities are believed to have acted as historical refugia for rainforest fauna when the rainforests contracted as a result of aridifi cation during the last glacial maximum of the Pleistocene (Nix and Kalma 1972;Barlow and Hyland 1988;McKenzie et al 1991). Some examples of taxa strongly associated with mangroves on the Kimberley islands include birds such as the Kimberley Flycatcher, Largebilled Gerygone and Mangrove Robin, and bats such as Scotorepens sanborni, Mormopterus loriae cobourgiana and Pipistrellus westralis (McKenzie and Rolfe 1986;McKenzie et al 1991;Johnstone 1990;McKenzie and Bullen 2012). The more extensive mangrove stands on the islands sampled during the KIBS tended to be in the southern section of the Northern Kimberley coastline, for example, Sunday, Kingfi sher, Wulalam and Long islands.…”

“…The taxonomic groups targeted include the nonvolant mammals, bats, reptiles, frogs, land snails and vascular plants, and birds were sampled opportunistically (see Gibson and McKenzie 2012a). Assessments of the biogeographic patterns in relation to island-wide attributes for each of these groups have been presented in a series of papers (see Doughty et al 2012;Gibson and Köhler 2012;Gibson and McKenzie 2012b;McKenzie and Bullen 2012;Pearson et al 2013;Palmer et al 2013;Lyons et al 2013). Overall, the survey revealed the presence of additional island populations of many vertebrates, and more than doubled the species lists for most of the islands where prior biological information existed.…”