EMERGENCE, ECHOLOCATION, DIET AND FORAGING BEHAVIOR OF MOLOSSUS ATER (CHIROPTERA, MOLOSSIDAE)

Between 4 and 16 January 1996, during a period of cool weather, we stu died the emergence and foraging behavior of Molossus ater at a site ne ar Akumal, in the Yucatan Peninsula in Mexico. The bats, a colony of a t least 32 individuals, roosted in a north-facing cinder block wall, a nd emerged about sunset. Emerging bats were usuary clustered in time, while those returning usually were not. Radio-cracking revealed that t he bars foraged for short periods (mean 26.8 min) and captures of retu rning individuals indicated that 27 of 28 had fed, taking, on average, 4.4 g of insects, mainly hydrophilid beetles. On some nights, few or none of the radio-ragged bats emerged from the roost. Calculations con cerning the costs of flight and roosting show that they were more than covered by the energy intake the bars achieved. Molossus ater have hi gh aspect ratio (8.3-9.1) wings and high wing-loadings of 17.55-24.15 N/m(2). When searching for prey, these bats produce long (12.3 ms), na rrowband(3.8 kHz), echolocation calls that sweep from 27.6-23.8 kHz. E nergy was not limiting for these bats at the time of our study.