Before the Spanish study, some scientists had been sceptical about the mammals attacking migratory birds Before the Spanish study, some scientists had been sceptical about the mammals attacking migratory birds Bats are generally viewed as harmless, if spooky, creatures of the night. But scientists have revealed a more savage side, after witnessing a greater noctule bat – Europe’s largest bat species – hunting, killing and devouring a robin mid-flight. The grisly recording reveals the bat as a