USE OF VISION BY LITTLE BROWN BAT, MYOTIS-LUCIFUGUS, UNDER CONTROLLED CONDITIONS

Two groups of little brown bats (M. lucifugus), one with auditory impairment and one untreated, were scored as they flew through a vertical string maze under three light conditions: full room light, very dim light, and total darkness. A total of 960 test flights was scored. Both groups collided most often with the maze in the presence of full light. On flights in dim light when the contrast between maze and surround was high, the 'deafened' animals collided significantly less with the maze than they did in total darkness. When the contrast in dim light was low, collision scores were similar to those in darkness or higher. The impairment of obstacle avoidance in full light is discussed in relation to previous failures to demonstrate pattern vision in these animals. The enhancement of obstacle avoidance in dim light and high contrast is interpreted as evidence that these animals can use pattern vision while in flight and is discussed in relation to current research on longdistance navigation and homing by bats. © 1969.