For nearly 25 years, scientists have puzzled over how Europe’s largest bat, the greater noctule, manages to eat small birds.
The mystery has finally been solved. New research shows that these bats are capable of chasing, catching, and eating birds more than a kilometer above the ground—all while staying in flight.
The findings, published in Science, reveal a hidden drama that plays out in the night skies as billions of songbirds migrate under cover of darkness.
These birds often travel at night to avoid daytime predators like hawks, but they are not safe from bats.
To uncover the bats’ secret, researchers fitted them with tiny “backpacks” containing biologgers, developed at Aarhus University in Denmark.
These miniature devices recorded the bats’ altitude, speed, wing movements, and echolocation calls.
By virtually “riding” on the bats’ backs, the scientists could observe what happened when a bat set its sights on a bird.
The recordings showed that the greater noctule flies high into the night sky to hunt, using powerful, low-frequency echolocation calls that birds cannot hear. Once a target is detected, the bat attacks with bursts of rapid calls and daring aerial dives, sometimes resembling fighter jets in a dogfight.
In one case, a bat dove for 30 seconds before giving up, as birds are extremely agile in flight.
In another, a bat chased a robin for nearly three minutes before finally catching it near the ground. The microphones recorded 21 distress calls from the bird, followed by 23 minutes of chewing sounds as the bat consumed its prey while flying low.
Evidence from DNA and X-ray analysis of bird wings found beneath roosts confirmed that greater noctules bite off the wings to reduce drag, then hold the body in a pouch of skin between their hind legs to eat mid-flight.
The discovery is remarkable because a robin can weigh nearly half as much as the bat itself. Laura Stidsholt, an assistant professor at Aarhus University and one of the study’s lead authors, compared it to a person catching and eating a 35-kilogram animal while jogging. “It’s fascinating that bats can do this while flying,” she said.
The road to this breakthrough was long. Spanish bat expert Carlos Ibáñez first found bird feathers in bat droppings nearly 25 years ago and proposed that greater noctules eat songbirds in flight. Many were skeptical.
Over the years, his team used everything from hot-air balloons with microphones to radar and GPS trackers, but the technology was never light enough for the bats to carry comfortably. With the invention of tiny biologgers, however, the team finally gathered the evidence needed—just as Ibáñez approached retirement.
The discovery is not just a scientific triumph; it also has conservation importance. Greater noctules are rare, endangered in many regions, and depend on forest habitats that are rapidly disappearing.
While the thought of bats hunting birds may sound alarming, their numbers are too low to pose a serious threat to songbird populations. Instead, understanding their unique hunting behavior is crucial for protecting this extraordinary species.
As lead author Elena Tena put it, listening to the bird’s distress calls fade into silence and chewing noises was both unsettling and extraordinary. “It was proof of what we had been searching for all these years,” she said.
