The image of the bat with blood and feathers around its mouth perfectly illustrates the story now published in Science by an international research team. Credit: Jorge Sereno
After nearly 25 years of investigation, scientists have solved the mystery. Europe’s largest bat not only eats small birds, it hunts and catches them more than a kilometer above the ground—and consumes them while still in flight.
An international group of scientists has uncovered how Europe’s largest bat species hunts and eats small birds. Their findings, published in Science, reveal a remarkable story of nighttime pursuit, precision, and predation.
Each year, billions of songbirds migrate between their breeding and wintering grounds. Many species choose to fly at high altitudes and during the night, a strategy that helps them avoid daytime predators. However, the darkness does not guarantee safety—bats are active hunters after sunset.
Riding on the bat’s back
To study this behavior, researchers effectively “rode along” with Europe’s largest bat, the greater noctule (Nyctalus lasiopterus), by fitting the animals with miniature “backpacks” equipped with biologgers created at Aarhus University. These devices tracked movement, altitude, acceleration, and sound (including echolocation), allowing scientists to observe how the bats locate and capture prey more than a kilometer above the ground in complete darkness.
Credit: Elena Tena
The study revealed that greater noctules can ascend high into the night sky to hunt unsuspecting birds. Unlike many insects, birds cannot detect the bats’ echolocation calls and often remain unaware of the approaching threat until it is too late to evade capture.
The bats’ success lies in their powerful, low-frequency echolocation calls, which enable them to detect targets over long distances. Once they have identified a bird, they close in quickly, signaled by a rapid series of short echolocation pulses just before the strike.
The study revealed that greater noctules can ascend high into the night sky to hunt unsuspecting birds. Unlike many insects, birds cannot detect the bats’ echolocation calls and often remain unaware of the approaching threat until it is too late to evade capture.
The bats’ success lies in their powerful, low-frequency echolocation calls, which enable them to detect targets over long distances. Once they have identified a bird, they close in quickly, signaled by a rapid series of short echolocation pulses just before the strike.
Daring dives
Data recorded by the biologgers revealed that the bats chased their prey by performing steep, high-speed dives toward the ground, similar to fighter planes engaging in aerial combat.
During these descents, which lasted 30 and 176 seconds respectively, the bats increased their wingbeat rate and force while tripling their acceleration and producing a constant stream of attack calls.
In one case, the bat that dived for 30 seconds eventually abandoned the chase—birds, after all, can be just as agile in the air as bats.
https://www.youtube.com/watch?v=jRvbwp3hnKI&t=1s
The bat attack visualized from data from the biologger. The greater noctule bat ascends to high altitudes to detect its songbird prey. After a vertically downwards sprint of several minutes, the bat finally catches its prey. The audio is sped up and affected by wind noise. Thus, the chewing sound is difficult to perceive.
Credit: Laura Stidsholt
The second bat, however, caught its prey close to the ground after nearly three minutes of pursuit. The microphone recorded 21 distress calls from the bird (a robin), followed by 23 minutes of chewing sounds from the bat as it flew at low altitude.
Combined with X-ray and DNA analyses of songbird wings found under the bats’ hunting grounds, the data from just two bats paint a clear picture of the final act:
The bats kill the birds by biting them, then bite off their wings – probably to reduce weight and drag. The researchers believe that the bats then stretch the membrane between their hind legs forward like a pouch and eat the bird mid-flight.
Wild maneuvers
“We know that songbirds perform wild evasive maneuvers such as loops and spirals to escape predators like hawks during the day – and they seem to use the same tactics against bats at night. It’s fascinating that bats are not only able to catch them, but also to kill and eat them while flying. A bird like that weighs about half as much as the bat itself – it would be like me catching and eating a 35-kilo animal while jogging,” says Assistant Professor Laura Stidsholt from the Department of Biology at Aarhus University.
She is one of the study’s lead authors and has for several years refined and applied biologger technology in her bat research, leading to numerous scientific papers – and surprises.
At the time when she finalized the data collection and did the analysis for this paper, Stidsholt was a Postdoc at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in Berlin.
A 25-year-old hypothesis
For a couple of decades, it has been known that at least three large bat species feed on small birds in flight. Much of this knowledge stems from the tireless work of Spanish bat researcher Carlos Ibáñez and his colleagues at the Doñana Biological Station (CSIC) in Seville.
Nearly 25 years ago, Ibáñez discovered feathers in the droppings of greater noctules and has since gathered mounting evidence that these bats catch and eat songbirds.
Credit: Elena Tena
The Doñana research team has long studied the greater noctule, a rare and difficult-to-monitor forest species. They have installed “smart” artificial roosts in the Doñana Reserve and implanted each bat with a tiny subcutaneous microchip that is detected by an antenna in each roost. The system logs the bats’ movements, stores the data, and sends alerts directly to the team’s mobile phones.
Years of pursuit
For years, the researchers tried to uncover exactly how the bats managed to catch and eat birds in flight.
“We knew that the greater noctule catches and eats insects in flight, so we assumed it did the same with birds – but we needed to prove it,” says Carlos Ibáñez.
The hypothesis was initially met with skepticism within the scientific community, since some birds weigh up to half the weight of the bat itself and thus might reduce the bats’ ability to fly.
The Doñana research team has long studied the greater noctule, a rare and difficult-to-monitor forest species. They have installed “smart” artificial roosts in the Doñana Reserve and implanted each bat with a tiny subcutaneous microchip that is detected by an antenna in each roost. The system logs the bats’ movements, stores the data, and sends alerts directly to the team’s mobile phones.
Years of pursuit
For years, the researchers tried to uncover exactly how the bats managed to catch and eat birds in flight.
“We knew that the greater noctule catches and eats insects in flight, so we assumed it did the same with birds – but we needed to prove it,” says Carlos Ibáñez.
The hypothesis was initially met with skepticism within the scientific community, since some birds weigh up to half the weight of the bat itself and thus might reduce the bats’ ability to fly.
Credit: Elena Tena
Because bats hunt at night, it is impossible to film the chase. Researchers instead tried surveillance cameras on roosts, military radar, ultrasound recorders attached to hot-air balloons, and GPS trackers. The main challenge was finding equipment light enough for the bats to carry.
Now, with the lightweight devices from Aarhus University – and just as Carlos Ibáñez approaches retirement – the team has finally caught a greater noctule in the act.
Essential for bat conservation
For Elena Tena, also a lead author of the study, hearing the sound recording of the bird’s distress calls followed by sudden silence and long chewing noises was an intense moment after so many years of effort:
“While it evokes empathy for the prey, it is part of nature. We knew we had documented something extraordinary. For the team, it confirmed what we had been seeking for so long. I had to listen to it several times to fully grasp what we had recorded.”
Fortunately, there is little cause for concern about bats threatening songbird populations. The greater noctule is extremely rare and, in many areas, endangered as its forest habitats disappear.
Thus, this discovery has important conservation implications. Understanding the greater noctule’s ecology and hunting behavior is essential for designing effective conservation and management strategies.
Because bats hunt at night, it is impossible to film the chase. Researchers instead tried surveillance cameras on roosts, military radar, ultrasound recorders attached to hot-air balloons, and GPS trackers. The main challenge was finding equipment light enough for the bats to carry.
Now, with the lightweight devices from Aarhus University – and just as Carlos Ibáñez approaches retirement – the team has finally caught a greater noctule in the act.
Essential for bat conservation
For Elena Tena, also a lead author of the study, hearing the sound recording of the bird’s distress calls followed by sudden silence and long chewing noises was an intense moment after so many years of effort:
“While it evokes empathy for the prey, it is part of nature. We knew we had documented something extraordinary. For the team, it confirmed what we had been seeking for so long. I had to listen to it several times to fully grasp what we had recorded.”
Fortunately, there is little cause for concern about bats threatening songbird populations. The greater noctule is extremely rare and, in many areas, endangered as its forest habitats disappear.
Thus, this discovery has important conservation implications. Understanding the greater noctule’s ecology and hunting behavior is essential for designing effective conservation and management strategies.
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