Bioacoustic and behavioral correlates of spatial memory in echolocating bats.

Abstract

Echolocating bats face a unique orientation problem due to their reliance on echolocation over visual orientation. Each observation (sonar vocalization) only contains information about objects in front of and within at most 5–10 m of the animal. Because their behavior extends over much larger distances, spatial memory might be particularly important during foraging activity and free flight to integrate the shorter views provided by sonar. To investigate memory for object locations, Eptesicus fuscus were allowed to fly freely in an instrumented flight room populated with sparse obstacles (hanging chains). Bat position and vocalization were monitored with a stereo-registered pair of thermal cameras and an array of ultrasonic microphones synchronized to the video. Data were analyzed for correlates of spatial memory-flight path dynamics, head aim, and temporal structure of echolocation signals. Data recorded from bats free-flying in the chain array are consistent with memory of obstacle locations and high-level planning of a flight path through the entire space. These data reflect the behavior of bats flying in natural conditions. [Work supported by ONR and NSF.]