Evidence for the use of vision in diurnal orientation of the bat Myotis austroriparius

Abstract

Normal, ear-plugged and blindfolded southeastern brown bats, Myotis austroriparius, were released during the day at two stations 500 and 750 ft from the home cave. Thirty-two (33·3 per cent) of ninety-six normal bats returned to the main or secondary entrances of the cave as compared with five (12·5 per cent) of forty earplugged and none of forty-five eye-covered subjects. More bats returned from the south, the direction in which the bulk of the colony went during the evening flight two nights before the experiment, thus suggesting that differential familiarity with the local terrain may have been a factor in homing success. In addition to the fact that none returned to the cave area, blindfolded bats were obviously more disoriented than either controls or ear-plugged subjects. These results thus appear to provide further evidence that vision in bats of the suborder Microchiroptera is better developed than generally supposed and that at least under certain conditions visual cues play a significant role in the orientation of these animals. It is suggested that auditory guidance from normal bats may play a major role in the homing of blindfolded bats.