ORIENTATION BY THE BAT PHYLLOSTOMUS DISCOLOR (PHYLLOSTOMIDAE) ON THE RETURN FLIGHT TO ITS RESTING PLACE

Bats have a well-developed spatial memory, which enables them to navig ate even when the conditions are extremely unfavourable for orientatio n. However, if they were to adhere too strictly to a flight path plann ed from memory and independent of exteroceptive control, they would be in danger of colliding with unexpected obstacles. In the experiments described here, Phyllostomus discolor that had familiarized themselves with an octagonal flight arena developed a clear preference for certa in resting sites and were able to fly to these sires without recourse to external orientational cues. Proximal and distal cues were ruled ou t separately, by rotating the direction in which the bars started out within the arena or by rotating the entire arena in the room. Furtherm ore, by marking the preferred sire with a visible identifier it was sh own that even when additional aids to orientation are available, the b ats do not make use of them. On the other hand, all the bats tested re sponded immediately to a reduction of the landing area, demonstrating that they are capable of incorporating exteroceptive information into the orientation process in certain circumstances.