THE ORIENTATION BEHAVIOR OF THE LESSER SPEARNOSED BAT, PHYLLOSTOMUS DISCOLOR (CHIROPTERA) IN A MODEL ROOST - CONCURRENCE OF VISUAL, ECHOACOUSTICAL AND ENDOGENOUS SPATIAL INFORMATION

The orientation behaviour of bats (Phyllostomus discolor, Phyllostomid ae), flying inside an octagonal ''roost-like'' chamber (o: 100 cm; h: 150 cm) was examined. It has been shown that the bats begin turning ma noeuvres during flight by turning their head towards the direction the y intend to proceed to. During early phases of the flights, cumulative navigation errors were evident, indicating that endogenous spatial in formation plays a major role in the orientation of the bats. During la ter phases of the flight this error is diminished again. So it can be concluded that the bats start to use exogenous spatial information for orientation while approaching the target. In order to investigate the relative importance of vision, echolocation and endogenous spatial in formation for approaching the roost, the landing lattices inside the t est arena were changed for non-grid dummies. We found that: 1. combine d visual and endogenous information are more important than echoacoust ical cues, 2. the bats learned quickly to switch their orientation beh aviour in order to get a better performance in avoiding the dummies, 3 . the learning performance was influenced by the visual similarity of dummies and the real landing lattice.