Batman and Robin make a dynamic duo, but it might shock the Caped Crusaders to learn that real bats and robins are sometimes mortal enemies. Now scientists have found the first evidence of stunts that would make comic book illustrators proud: A species of bat pursues and sinks its teeth into unsuspecting birds in midair.
Many tropical bats catch birds perching in trees. But proving aerial combat was harder; after all, the greater noctule bat, Nyctalus lasiopterus, hunts at night, hundreds of meters above the mountainous forests of northern Spain. Researchers led by Carlos Ibanez at Spain's Estación Biológica de Doñana in Seville assembled their evidence from an ongoing study of bat fecal pellets.
The team found bird feathers in a substantial number of their 14,000 samples, as much as 70% during peak autumn migration. Bat feces were most likely to contain feathers during this time of year, when some 5 million to 10 million birds are estimated to fly over Spain. Since the bats hunt by night and the birds only roost by day, the capture must happen mid-flight, they argue in the 7 August issue of the Proceedings of the National Academy of Sciences. Furthermore, the greater noctule bat's 40-centimeter-plus wingspan and low-frequency sonar are well-suited for hot pursuit in the wide open sky, but not for finding birds in crowded tree canopies.
"This is as good a smoking gun as you get," said neuroscientist James Simmons, an echolocation expert at Brown University in Providence, Rhode Island. "Next to actually videotaping it, that's about the best they can do." And if one species of bat can hunt on the wing, it could be happening wherever large bats and migratory birds overlap.