Head waggles and ear wiggles help bats hunt

Head tilts are one of the more adorable traits exhibited by domestic dogs, but did you know bats do it too? A study published in PLOS Biology into bat behaviour found these little movements help bats track prey with incredible precision.

Melville Wohlgemuth at the University of Maryland observed this subtle behaviour among bats during previous research and was reminded of his pet pug.

“It’s an adorable behaviour and I was curious about the purpose,” he explains.

“I wanted to know when bats were doing this and why. It seemed to occur as bats were targeting prey, and that turns out to be the case.”

According to his and colleagues’ research, the head-tilt appears to be a physical action used to enhance existing sensory awareness, a phenomenon that’s used throughout the animal world – including among humans.

To help them navigate the world, bats use echolocation. They send out high-frequency chirps and use echoes to figure out where they are and what’s around them.

Wohlgemuth’s research team used recording devices to observe three big brown bats (E. fuscus), with a particular focus on when bats waggled their heads and wiggled their ears.

Their results suggest these movements occur when bats are hunting prey, and, incredibly, appear to synchronise with their sonar vocalisations.

To reach this finding, the researchers trained the bats to remain stationery while tasty mealworms were presented around them.

The bats were fitted with reflectors on their head and ears so their subtle movements were easy to observe and record.

The findings showed that bats’ head waggles, which occurred about once per second, adjusting the relative elevation of each ear – and coincided with a worm’s change in direction. Meanwhile, they very subtly moved their ears when the prey came closer to the bat.

Most interestingly, these slight movements coincided with the bat’s vocalisations, which probably allow it to accurately track the whereabouts of its prey.

“Bats showed an increase in the number of head waggles after the conclusion of a sonar sound group, suggesting the bat’s dual control over the timing and reception of sonar signals during target tracking,” the paper explains.

Study co-author Cynthia Moss, also at University of Maryland, says the analysis can be used to better understand the subtle, sense-related movements of other animals, such as the ear twitches of a cat or a human’s eye movements.

“By studying these movements,” she says, “we as humans can get insight into how movement helps animals sense their environment.”

As well as contributing to our understanding of neuroscience, the researchers point out their findings could be useful in developing robots that mirror sensory systems.