Resource partitioning by two closely-related sympatric freetail bats, Mormopterus spp.

Abstract

Resource partitioning enables closely-related, morphologically similar species to coexist. We investigated resource partitioning by two closely-related insectivorous bats, the Eastern Freetail Bat Mormopterus sp. 2 and Southern Freetail Bat Mormopterus sp. 4, within the zone of sympatry in northern Victoria. We sampled 36 sites with harp-traps and bat detectors; caught a total of 159 Mormopterus, and identified 961 echolocation passes. Analysis of wing dimensions suggested that Mormopterus sp. 4 was a faster, less manoeuvrable flyer than Mormopterus sp. 2. This was supported by greater activity levels at more open and less structurally complex sites. Mormopterus sp. 2 was significantly more active in riparian habitats, which may be due to a preference for more mesic environments. Observations of flight patterns revealed slight differences in the two species' microhabitat use, however both species flew predominantly in the spaces between trees. Hemiptera was the most consumed arthropod order in the diet of both species. The subtle, yet significant differences in wing morphology were reflected in the slight differences in microhabitat use by the two species, and the presence of superabundant Hemipteran prey may allow the two species to coexist.