Echolocating free-tailed bats use vision and hearing but not magnetoreception when navigating a maze

Insectivorous bats navigate mainly by echolocation, but may also use visual, olfactory, and magnetic cues when travelling long distances. Parsing the relative contributions of different senses for navigation is difficult in wild bats. In the lab, spatial navigation in rodents is often studied using different maze assays, including the widely employed multiple T-mazes. Here, we trained crawling Mexican free-tailed bats (Tadarida brasiliensis) to navigate a multiple T-maze within an artificial magnetic field and then manipulated the sensory environment to quantify the relative importance of vision, hearing and magnetic field cues on their navigation performance. We predicted that in addition to echolocation, visual and geomagnetic sensory cues might provide significant contributions to bat navigation performance. We hypothesized that (1) randomly reversing the polarity of the magnetic field, (2) changing color or removing light from the arena, or (3) presenting an acoustic jamming stimulus would increase mean maze travel times. Results showed that reversing the magnetic field had no significant impact on maze travel times under any conditions. However, in total darkness, mean travel times increased by 75% relative to both broad spectrum white light and red light. Travel times under red light were longer but not significantly different from white light. Playing an acoustic jamming stimulus mimicking the pulses of other bats significantly increased mean travel times by ~ 50%. These results show that insectivorous bats supplement biosonar with visual cues during navigation, but we found no evidence of a contribution from magnetoreception.