Structure of Bat Guilds in the Kimberley Mangroves, Australia

(1) Deterministic guilds have been predicted to occur in stable, persistent communities. Mangrove communities in the Kimberley of Western Australia include large, isolated stands that are stable in terms of floristic composition and vegetation structure. A selection of stands was sampled for bats belonging to the insect foraging guild. (2) The potential foraging niche of each bat species was estimated in terms of the bat's flight morphology (aerodynamic characteristics) at minimum wing loading. These estimates were used to analyse the structure of the guild observed in each mangrove stand. (3) The observed guilds had a deterministic structure. The flight morphologies of species that foraged in the same stand showed almost no overlap even though each of these observed guilds occupied almost the same total area of morphological space as the entire pool of potential colonizers. In contrast, guild structures generated stochastically from the pool of potential colonizers included significant overlap. (4) Available flight space in the mangal was arbitrarily divided into five foraging microhabitats so that species' realized foraging niches could be estimated from field observations and used to interpret the morphological analysis. (5) Differences in species' flight morphologies could be related to vertical and horizontal foraging microhabitats but the morphological data indicated that a narrower partitioning of foraging zones actually occurred.