Vampire bats are a Halloween staple, and now they’ve obtained firm. One other bat species snatches birds out of the air for a ugly midnight feast.
Songbird DNA has beforehand proven up within the guano of three bat species, so researchers knew these flying mammals had been consuming extra than simply bugs. However how, precisely, does a bat hunt a hen? It seems that Europe’s largest bat, the larger noctule, is a formidable aerial hunter that captures, dismembers and consumes migrating songbirds for the last word in-flight meal, researchers report within the Oct. 9 Science.
For years, scientists have tried to grasp how these bats seize prey, however it’s difficult to know what animals are doing excessive within the evening sky. The answer: Monitor their actions, says bioacoustician Ilias Foskolos of Denmark’s Aarhus College. He and his colleagues geared up larger noctules (Nyctalus lasiopterus) with biologgers. These units function a number of sensors, together with accelerometers to document 3-D motion, magnetometers to log route, altimeters to measure altitude and microphones.
“Utilizing [these] high-tech approaches, the Science paper is the primary to trace the looking maneuver of a larger noctule chasing and catching a robin,” says Danilo Russo, a bat ecologist on the College of Naples Federico II in Italy who was not concerned with the examine. “Though there isn’t a visible commentary of the looking episode, in my view, this examine nonetheless offers compelling proof that birds are caught in flight.”
Not one of the sensors recorded video of the bats’ actions or meals, however they did observe every bat’s nightly actions, giving researchers a peek into their mysterious looking behaviors. Listening to the recordings “is like flying with the bats,” says Elena Tena, a bat conservationist at Doñana Organic Station in Seville, Spain, the place the staff captured and tagged bats for the examine. “You’ll be able to hearken to the flapping” of their wings and the calls of frogs because the bats wing their approach throughout Doñana’s marshes, she says.
Microphones additionally captured feeding buzzes because the bats approached their prey. These buzzes, adopted by chewing sounds, indicated a profitable hunt, Tena says. A lot of the 611 looking occasions concerned bugs close to the bottom, however two stood out. In each circumstances, the bats flew to excessive altitudes — above the peak of migrating songbirds, greater than 1,200 meters up. The predators then homed in on a hen and approached with loud feeding buzzes.
“As a result of the frequencies are so excessive, the birds … can’t hear them,” Foskolos says. Each birds responded on the final second, most likely reacting to the bat’s contact or the sound of its wings. “They most likely do dives and spirals and complex maneuvers,” to evade the bats, he says. “They appear to go vertically down, as a result of that’s what we see from the info.”
One hen escaped close to the bottom. The opposite wasn’t so fortunate. The microphones captured its misery calls adopted by a 23-minute in-flight meal. “The bat was flying usually due to the accelerometer information, and chewing and echolocating on the similar time,” Tena says. “Generally you possibly can hear that it should be biting bone.”
Eradicating wings appears to be a part of their course of. “Generally, after we had been capturing [bats], out of the blue, some wings [would] fall to the bottom,” Tena says. DNA evaluation of wounds on the wings confirmed the chew of a larger noctule bat. And netted bats of the identical species have sometimes been caught with red-stained lips and feathers hanging from their mouths.
Although the staff now has proof displaying how these bats prey on songbirds, “we nonetheless know little or no about this species,” Tena says. This examine is a leap ahead in understanding the larger noctule’s function as certainly one of Europe’s high predators.
