Using a special app created by a computer science friend, Lilly logged the amount of time that the squirrel spent either freezing, foraging, fleeing, resting, or standing. Then, the squirrel would hear either several minutes of casual bird talk that had been recorded around a bird feeder, or several minutes of silence that was recorded around the same feeder at night. Once she found a suitable eastern gray squirrel, she'd set up her equipment and hide behind a bush to perform the experiment.įirst, the squirrel would hear the recorded cry of a hawk. "And I put those on my bicycle, and basically rode around town looking for squirrels." "It definitely did look very ridiculous," says Lilly, who explains that she set up audio equipment in a couple of repurposed cat litter buckets. Her idea for a study of how squirrels respond to lighthearted bird tweets got picked up and expanded by fellow former student Marie Lilly, who did the fieldwork one cold January in Oberlin.
"I wanted to know if they might be paying attention to other information, as well," says Emma Lucore, one of Tarvin's former students. While other researchers have focused on how animals tune into other species for warnings of danger, his team focused on whether animals also watch their neighbors for signs of safety. "This has been found in a variety of squirrels - ground squirrels, tree squirrels.
"Lots of animals listen in on the alarm calls of other species," says Keith Tarvin, a behavioral ecologist at Oberlin College in Ohio. The findings, described in the journal PLOS One, add to a growing body of research that animals take advantage of all available "public information" when trying to assess threats in their environment. Researchers have found that a squirrel becomes incredibly vigilant when it hears the shriek of a red-tailed hawk, but it will relax and resume its food-seeking behavior more quickly if the predator's call is immediately followed by the easygoing tweets of unconcerned birds. Squirrels eavesdrop on the casual chitchat of birds to figure out when it's safe enough to be out in the open and foraging for food. The sounds of pleasant, relaxed bird chatter made eastern grey squirrels resume foraging more quickly after hearing the sounds of a predator, researchers found.
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