Analyze This: Some bats feast on songbirds midflight

Vampire bats are a staple of Halloween. But they’re not the lone bats that merit the rubric of creepy creature. Another species snatches birds retired of the aerial for a gruesome midnight feast.

Songbird DNA has shown up earlier successful the poop of 3 bat species. So researchers knew these flying mammals ate much than conscionable insects. But however does a bat hunt a bird? It turns retired that Europe’s largest bat, the greater noctule, can capture, rip isolated and devour songbirds midflight.

Researchers shared these findings October 9 in Science.

Flying with bats

For years, scientists person wondered however greater noctules (Nyctalus lasiopterus) seizure prey. But it’s hard to cognize what animals are doing precocious successful the nighttime sky. The solution: Track their movements, says Ilias Foskolos. He studies the acoustics of surviving things astatine Aarhus University successful Denmark.

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

These sensors tracked the bats’ nightly activities. Listening to the recordings “is similar flying with the bats,” says Elena Tena. You tin perceive their wings flap and frog calls arsenic they alert implicit marshes. Tena is simply a bat conservationist astatine Doñana Biological Station successful Seville, Spain. That’s wherever the squad captured and tagged bats for the study.

Microphones besides captured the feeding buzzes bats made arsenic they approached their prey. These buzzes, followed by chewing sounds, indicated a palmy hunt.

The vertebrate calls recorded during the bat onslaught lucifer the distress calls of a European robin, shown here. Laura Stidsholt

Om-nom-nom

The researchers logged 611 hunting events. Most involved insects adjacent the ground. But 2 stood out. In some cases, the bats flew supra the tallness of migrating songbirds — much than 1,200 meters (nearly 4,000 feet) high. The bats past homed successful connected a vertebrate and approached with feeding buzzes.

The pitches, oregon frequencies, of those buzzes are excessively precocious for birds to hear, Foskolos says. Both birds responded astatine the past moment. They were apt reacting to the bat’s interaction oregon the dependable of its wings. “They astir apt bash dives and spirals” to escape, Foskolos says. “They look to spell vertically down.”

One vertebrate escaped adjacent the ground. The different wasn’t truthful lucky. Microphones captured its distress calls followed by a 23-minute in-flight meal. Accelerometer information showed the bat was flying usually portion it chewed, Tena says. “Sometimes you could perceive that it indispensable beryllium biting bone.”

Removing wings seems to beryllium portion of the bats’ process. “Sometimes, erstwhile we were capturing [bats], suddenly, immoderate wings [would] autumn to the ground,” Tena says. DNA from wounds connected the wings confirmed the wound of a greater noctule bat. And captured bats of the aforesaid taxon person sometimes been caught with red-stained lips and feathers hanging from their mouths.

Though determination is nary video of the bats hunting birds, the survey “provides compelling grounds that birds are caught successful flight,” says Danilo Russo. This bat ecologist astatine the University of Naples Federico II successful Italy was not progressive with the study.