Egyptian fruit bats exhibit precise 3D spatial memory that eclipses sensory information

Abstract

Egyptian fruit bats (Rousettus aegyptiacus) have well-developed vision and lingual echolocation, which provide complementary sensory information to execute natural behaviors, such as obstacle avoidance and landing. However, spatial memory can reduce the computational load in natural tasks and there is evidence that bats sometimes fail to use sensory information when they operate in familiar surroundings. Here we investigate the precision of this bat species’ spatial memory for a landing location when it has access to vision and sonar echoes and when it has access to sonar echoes alone. Animals were trained for about 10 days to find a 5 cm diameter landing platform at a fixed location in a 2.5 × 6 m2 flight corridor and later tested when the landing platform was shifted in azimuth and elevation by 5–30 cm. The bat’s 3D flight trajectory was tracked with high-speed video cameras and its sonar inspection of objects was quantified with an ultrasound microphone array that permits reconstruction of the sonar beam aim. Our data suggest that spatial memory in Egyptian fruit bats is highly precise and eclipses multimodal sensory information. This bat species’ robust reliance on 3D spatial memory may support long-distance navigation and forage in the natural environment.