Abstracts - Deutsche Zoologische Gesellschaft

24 Behavioral Biology SymposiumO BB.3 (Su) - ENForaging behavior and habitat selection in pit-building antlionsInon ScharfDepartment of Life Sciences, Ben-Gurion University of the Negev, IsraelPit-building antlion larvae are holometabolous insects, constructing conical pits in sandy soils,which serve as traps for small arthropods. In a series of experiments, I investigated the effects offeeding regime, predator presence, sand depth, light conditions and temperature on foraging behaviorand habitat selection in antlions. As prey item increased in size antlions showed an increase of pitdimensions followed by a decrease, indicating that they consider both their satiation level and the expectedrate of prey arrivals. Antlions also reduce pit construction rate when exposed to predators. Incomparison to a sit-and-pursue antlion, which does not construct pits, I found that the latter reducedrelocation activity, while the former reduced pit construction rate. Sand depth may affect antlions’ability to evade predators. In deeper sand, antlions built larger pits and showed reduced relocationrate, emphasizing the importance of the habitat’s physical characteristics. Exposing the antlionsto constant light increased their tendency to construct pits, which were also larger than those constructedunder complete darkness. Finally, antlions demonstrated a context-dependent response totemperatures: At low temperatures they preferred illuminated microhabitats, while otherwise shadedmicrohabitats were chosen. In conclusion, antlions use a flexible and context-dependent foragingbehavior with respect to both their biotic and abiotic environments.O BB.4 (Su) - ENBig ears for bats: absolute size matters for foraging efficiencyBjörn M. Siemers 1 , Michael Stauss 2 , Hendrik Turni 31Sensory Ecology Group, Max Planck Institute for Ornithology, Seewiesen; 2 Institut für Verhaltensökologie,Universität Tübingen; 3 Museum für Naturkunde der Humboldt-Universität, BerlinMany predators find their food by listening for prey sounds. Bats do so when hunting in cluttered environmentswhere substrate echoes overlap and mask echoes from the prey. Within the largest genusof bats, Myotis, this strategy of detecting prey in clutter by listening for their sounds evolved severaltimes convergently. All of these “passive listening” specialists have large ears. In a comparativestudy comprising 31 Myotis species, we found that the absolute ear size of all six included “passivelistening” species was quite similar, irrespective of their body size. I.e, smaller “passive listening”species have ears much larger than predicted by the genus regression line for scaling of ear size withbody size whereas larger species do not. This suggests that a certain absolute ear size is requiredand sufficient for efficient detection and localization of rustling arthropods. To test the influence ofear size on the received sound amplitude, we measured idealized bat ears below, at and above thesize found in “passive listening” Myotis. Indeed, the typical ear size of “passive listening” speciesresulted in an increased sensitivity for the sonic frequencies that dominate arthropod rustling sounds.We conclude that absolute ear size matters to efficiently pick up and localize these sounds. Smallerspecies that specialized for “passive listening” foraging behaviour thus had to evolve very large earsrelative to their body size.