Melville Wohlgemuth, a postdoctoral fellow in the Department of Psychological and Brain Sciences, noticed one day that the bats he works with cocked their heads to the side, just like his pet pug.
“I wanted to know when bats were doing this and why,” he says. “It seemed to occur as bats were targeting prey, and that turns out to be the case.”
Using high-tech recording devices, Wohlgemuth determined that a bat’s head waggles and ear wiggles sync with the animal’s sonar vocalizations to help it hunt. The finding demonstrates how movement can enhance signals used by senses like sight and hearing—not just in bats, but in dogs and cats, and even in humans.
Bats use sonar-like echolocation—emitting sounds and listening for the echo—to detect, track, and catch prey; that is well-documented. But Wohlgemuth and his team are the first to show how the head and ear movements factor into the hunt.
These head and ear movements coordinated with the bat’s vocalizations, on a millisecond time scale, allowing the animal to pinpoint prey with considerably more accuracy.
Co-author Cynthia Moss, a professor in the department, said other studies on how animals and humans localize sound sources missed the importance of head waggles and ear movements, because laboratories typically observe the subject with a fixed head position. That’s not at all how bats or other animals operate in the real world, when their heads are free to move.
Moss compared the bat’s head and ear movements to other species that use active sensing—like the ear movements of a cat on alert or the head tilt of an owl, which are used to attend to important information.
“By studying this,” she says, “we can get insight into how movement helps animals sense their environment.”