Friday, 6 October 2017

This Caterpillar Mimics Bird Alarm Calls to Scare Away Predators

When attacked, the North American walnut sphinx lets out a full-body scream that can reach up to 80 decibels in volume.
October 02, 2017

North American walnut sphinx caterpillars tend to do more chewing than chatting, but when they’re an open beak away from becoming lunch, they’ll let out screams that shake them to their very core—and leave their predators shook, too. The two-inch-long larva contracts its body muscles to lets out an imitation seet call—a warning cry some songbirds emit when facing imminent danger such as a hawk. The theory is that this tricks its avian assailants into stopping their attacks and flying away, ensuring the safety of the otherwise vulnerable insect.

To test the success of the caterpillar's cries, Jessica Lindsay, an undergraduate student at the University of Washington, set up an experiment to analyze the birds' responses. After recording the insect's sounds—which can be as loud as a freight train from 50 feet away—she played them back to wild flocks at feeders. She then did the same with real seets from Black-capped Chickadees and compared the two sets of reactions. Turns out, both calls made the would-be diners dive for cover. Her results, presented at the International Symposium on Acoustic Communication by Animals in July, were first reported by The Scientist.

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