The role of vision in the orientation of the echolocating bat, Myotis lucifugus.

Abstract

DAVIS & BARBOUR (1965) found that echolocating bats may utilize visual cues even when reliable, supra-threshold echolocation cues are available. The present experiment obtained a similar effect using a simultaneous discrimination paradigm. Ten Myotis lucifugus were rewarded with food for responding to a large-white triangle, but were not rewarded when they responded to a small-black triangle. The bats were given 20 trials each day until they achieved a criterion of 17 correct responses out of 20. They were then randomly divided into two groups and given 20 trials per day: 10 test trials to transfer test stimuli and 10 test trials to the original training stimuli. The transfer test stimuli for the test group were a large-white triangle versus a small-white triangle, and for the brightness test group a large-white triangle versus a large-black triangle. On the transfer tests the bats in the group did not run to either of the transfer test stimuli above chance, indicating a failure to discriminate size either visually or by echolocation. The bats in the brightness group, however, ran more frequently to the large-white stimulus than to the large-black stimulus, indicating a visual discrimination. During testing both groups indicated retention of the original training task. A blindfolded control group indicated that a size discrimination based on echolocation cues was possible. These results were interpreted as indicating that echolocation is not always the preferred modality for echolocating bats, and that under some conditions the bats may prefer to use visual cues.