Central-place foraging in nursing, arthropodgleaning bats

Central-place (CP) foraging theory predicts a positive correlation between the time a breeding CP forager spends in a patch and the distance of the patch to the CP. We found that nursing female Hemprich's long-eared bats (Otonycteris hemprichii Peters, 1859; Vespertilionidae) that forage around a lake in the Negev roost in only two areas: one 0.5-2 km (near) and one 9 km (far) from the foraging area. If these bats are CP foragers, then the strategies of the two groups should differ. We predicted that females roosting farther away would have longer but fewer foraging bouts. Using radiotelemetry, we measured the activity of six females from the near site and three from the far site. Without exception, females from the far site made a single, prolonged foraging bout each night, while females roosting nearby made several shorter bouts. Among the females from the near site, daily foraging time, mean daily foraging bout length, and first daily foraging bout length were all significantly and positively correlated with distance between the roost and the foraging site. Our data support the prediction that female O. hemprichii are CP foragers. We suggest that the females trade off using a safe roost site, distant from a choice foraging area, and lower nursing frequency against using a risky roost site close to the foraging area and greater nursing frequency.