Vampire bats are a staple of Halloween. But they’re not the only bats that deserve the title of creepy creature. Another species snatches birds out of the air for a gruesome midnight feast.

Songbird DNA has shown up before in the poop of three bat species. So researchers knew these flying mammals ate more than just insects. But how does a bat hunt a bird? It turns out that Europe’s largest bat, the greater noctule, can capture, rip apart and eat songbirds midflight.

Researchers shared these findings October 9 in Science.

Flying with bats

For years, scientists have wondered how greater noctules (Nyctalus lasiopterus) capture prey. But it’s hard to know what animals are doing high in the night sky. The solution: Track their movements, says Ilias Foskolos. He studies the acoustics of living things at Aarhus University in Denmark.

Foskolos and his colleagues equipped greater noctules with biologgers. These devices had multiple sensors. Accelerometers recorded 3-D movement. Magnetometers logged direction. Altimeters measured height in the sky, or altitude. And microphones captured sound.

These sensors tracked the bats’ nightly activities. Listening to the recordings “is like flying with the bats,” says Elena Tena. You can hear their wings flap and frog calls as they fly over marshes. Tena is a bat conservationist at Doñana Biological Station in Seville, Spain. That’s where the team captured and tagged bats for the study.

Microphones also captured the feeding buzzes bats made as they approached their prey. These buzzes, followed by chewing sounds, indicated a successful hunt.

Om-nom-nom

The researchers logged 611 hunting events. Most involved insects near the ground. But two stood out. In both cases, the bats flew above the height of migrating songbirds — more than 1,200 meters (nearly 4,000 feet) high. The bats then homed in on a bird and approached with feeding buzzes.

The pitches, or frequencies, of those buzzes are too high for birds to hear, Foskolos says. Both birds responded at the last moment. They were likely reacting to the bat’s touch or the sound of its wings. “They probably do dives and spirals” to escape, Foskolos says. “They seem to go vertically down.”

One bird escaped near the ground. The other wasn’t so lucky. Microphones captured its distress calls followed by a 23-minute in-flight meal. Accelerometer data showed the bat was flying normally while it chewed, Tena says. “Sometimes you could hear that it must be biting bone.”

Removing wings seems to be part of the bats’ process. “Sometimes, when we were capturing [bats], suddenly, some wings [would] fall to the ground,” Tena says. DNA from wounds on the wings confirmed the bite of a greater noctule bat. And captured bats of the same species have sometimes been caught with red-stained lips and feathers hanging from their mouths.

Though there is no video of the bats hunting birds, the study “provides compelling evidence that birds are caught in flight,” says Danilo Russo. This bat ecologist at the University of Naples Federico II in Italy was not involved with the study.

 “We still know very little about this species,” Tena says. Yet this research is a leap forward in understanding the greater noctule’s role as one of Europe’s top predators.

Data Dive:

1. What is altitude? What type of sensor measures movement in this dimension?
2. What is the range of altitudes shown on the graph? How does that compare to the height of migrating songbirds?
3. How does the bat’s altitude change as it searches for prey? Why might this be?
4. How does the bat’s altitude change as it attacks its prey? Why might this be?
5. What is sound frequency? Roughly what frequencies are the songbird’s distress calls? About how long does a distress call last?
6. What other types of measurements could offer more insight into how bats eat birds midflight? How would you graph those data?