Spatial foraging behavior and use of an urban landscape by a fast-flying bat, the molossid Tadarida australis

Insectivorous bats require different resources for diurnal roosting and nocturnal feeding, and sound conservation planning requires knowledge of both. However, ranging behavior and habitat use by foraging bats are poorly known, especially within urban ecosystems. We studied foraging flight behavior and use of an urban landscape by 14 white-striped free-tailed bats (Tadarida australis) in metropolitan Brisbane, Australia. Each evening, the bats emerged from day-roosts in tree-hollows and commuted rapidly to a feeding area (median travel speed 42.9 km/h, based on net distances moved during 10-20 min). Within 30 min from emergence their travel speed was greatly reduced (median 6.7 km/h) to a level that remained similar throughout subsequent hours while they foraged. Day-roosts were widely dispersed across the urban landscape, but foraging bats mostly restricted their movements to a localized area of a few kilometers diameter. This area was closer to a communal roost, visited periodically by all bats, than to their day-roosts (median distance from foraging bats to the communal roost 2.5 km; to their day-roosts 6.2 km). The bats showed a significant preference for foraging above floodplain habitat, and did not prefer to feed above remnant forest. T. australis appears tolerant of deforestation and capable of persisting in urban landscapes, provided that roost trees are protected. However, it remains unknown whether a sustained availability of aerial prey depends on floodplains remaining undeveloped.