For some of us, the first things you learn to understand in another language might be a bad word or two. When it comes to small birds who eavesdrop on other species, the thing that they were quick to pick up was something along the lines of “danger!” The findings were published in Current Biology this week.
Many vertebrate species, including people, gain critical information about possible hazards or injuries by listening in on other species’ alarm calls. Campbell’s monkeys, for example, will call out “Krak-oo” to warn others of danger such as a falling tree, but they’ll remove the suffix when it’s specifically a leopard. Diana monkeys remain on alert when they hear that “Krak.” How animals recognize the alarm calls of other species, however, is still a bit of a mystery.
An Australian National University team led by Robert Magrath wanted to better understand information flow among species in animal communities, so they designed an experiment to see if wild superb fairy-wrens (Malurus cyaneus) can learn to recognize previously unfamiliar alarm calls.
They trained individual wrens by broadcasting unfamiliar sounds: a thornbill alarm call or something totally synthetic. At the same time, the researchers hurled toward them a model glider of either pied currawongs or collared sparrowhawks. At first, the wrens ignored those sounds. After two days of training using fake predatory birds, eight out of 10 of the wrens would flee in response to those foreign sounds. “There was general disbelief and excitement when the bird learned the task perfectly,” Magrath says in a statement. The spread of anti-predator behavior within wild populations is rapid.
Rob Magrath with hawk model. Stuart Hay/ANU.
“Recognizing other species' calls is a remarkable ability, because there are lots of species in a natural community, and lots of different types of calls,” Magrath adds. “It's like understanding multiple foreign languages.”
Such cleverness can be used for deception too. The fork-tailed drongo, for example, is a master impersonator who can mimic the warning calls of species ranging from southern pied babblers to meerkats. When the dupes make a run for it, the kleptoparasites swoop in to steal their tasty, fat grubs.