Do Squirrels Eavesdrop on Birds?

Analysis by Dr. Karen Shaw Becker

squirrels bird chatter

Story at-a-glance -

  • Scientists say squirrels “eavesdrop” on the birds around them to get clues regarding how safe it is to venture out for food, essentially taking advantage of “public information” to assess threats in their environment
  • Researchers once thought of individual species in relation to how they respond to each other, but now they acknowledge the complexity in how communication can be vital between two or more different animal species
  • Scientists say some animals deliberately make audible “all clear” sounds as signals to let members of their own species know they’re safe to keep doing what they’re doing
  • Animals besides squirrels that pay attention to other animal species’ sounds to weigh their immediate security risks include monkeys and lizards
  • When a recording of a red-tailed hawk — a known threat to both squirrels and birds — was played as a trial to gauge the reactions of 54 squirrels, researchers found that when exposed to bird chatter, the squirrels had much lower levels of vigilance

You don’t have to look for very long before you notice that nature offers a number of breathtaking, mystifying and sometimes quirky phenomena — none more interesting than those emerging from the animal kingdom. There are fish that can be trained to do tricks, Norwegian forest cats that climbs down trees head first, and at least one species of which the male carries unborn young and eventually gives birth.

Maybe it won’t go down in the annals of weird science, but squirrels out gathering nuts can put two and two together when they hear predators nearby. Rather than scurrying back to their safe space immediately, they exhibit a rather human-like tendency: They start gathering their nuts faster.

Scientists say there’s a good reason for that. Squirrels effectively “eavesdrop” on the chatter of birds in their vicinity to get clues regarding the likelihood of safely leaving their homes (typically in trees but in some regions, in the ground), to venture out for food. According to NPR, birds are smart enough to “take advantage of all available ‘public information’ when trying to assess threats in their environment.”1 In addition:

“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.”2

Plenty of scientists have explored the implications of such behavior in the bushy-tailed, tree-dwelling rodent, described in the journal PLOS One,3 but other animals have exhibited similar behavior. Oberlin College behavioral ecologist Keith Arvin, one of three who conceived and worked on the study, said paying attention to other animal sounds to weigh immediate security risks has also been seen in monkeys and even lizards.

“Recognizing the alarms of other animals helps species reduce the energy they spend on unnecessary vigilance behavior. Alarm signals have a wealth of studies behind them. What they have found is that one member of a species will produce a specific sound, and nearby animals will run and hide.”4

The Power of the ‘Right’ Bird’s Call

Medical News Today explains that squirrels have “learned to listen”5 for audio cues as a means to increase their chances for survival. In addition, some animals deliberately make audible “all clear” sounds as signals to let members of their own species know they’re safe to keep doing what they’re doing.

Interestingly, studies say squirrels react to the sounds made by specific birds; in this case, American robins and black-capped chickadees. To test the theory, the scientists played a recording of a red-tailed hawk, a known threat to both squirrels and birds, to gauge the reactions of 54 squirrels. They moved to another area after each trial to avoid using the same squirrel twice. Within 30 seconds of releasing the hawk sounds, three-minute-long chickadee recordings were released. According to the study:

“Gray squirrels exposed to bird chatter expressed significantly lower and more rapidly declining levels of vigilance behavior than those exposed to ambient noise, suggesting they used information contained in bird chatter as a cue of safety.”6

‘Eavesdropping Squirrels Infer Safety From Bird Chatter’

Emma Lucore, a former student of Tarvin’s, explained that while some researchers have investigated the ways animals take their cues about the danger of a situation from other animals, she was curious about whether they also might be paying attention to signs from other animals that they could proceed in their foraging or other activities in the open without having to be on high alert.7

That’s how the idea evolved — one researcher musing about animal behavior and others picking up the concept to develop further. Fellow student Marie Lilly responded by putting the question to the test.

She set a up traveling fieldwork station in two repurposed cat litter buckets that masked her audio equipment and attached them to her bicycle. Then she “[b]asically rode around town looking for squirrels.”8 Once they were spotted — she looked specifically for eastern gray squirrels — she’d hide behind a bush to conduct the surveillance and record her findings:

“First, the squirrel would hear the recorded cry of a hawk. 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.

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. She also recorded whenever the squirrel looked up at the sky.”9

In the process, which took place on a cold night, it was impossible to tell the squirrels’ level of vigilance for a potential threat or, more precisely, the absence of a threat. What she found once her data was analyzed, however, was how obvious it was that when there was a background of mildly active bird chatter, the squirrels kept foraging, only more quickly.

How Bird Chatter Influences a Squirrel’s Sense of Security

Tarvin concluded that to mean the birds felt safe, which caused the squirrels to deduce that an interloper or predator hadn’t entered their immediate environment, so they could go about their business with much less trepidation.

Daniel Blumenthal, a behavioral ecologist at University of California in Los Angeles, was impressed with the study’s results, as well as the concept. “Most of us have been thinking about the risky side of things, not the safety side of things. Yet both sorts of public information are out there for the taking if you know what to clue in on.”10

Blumenthal noted that he and other researchers had been thinking of individual species in relation to how they respond to each other, but now, there’s more openness in regard to the complexity in how species communicate with each other, especially between two or more different animal species.

He noted that cues animals receive from other species “Can be really important in certain situations for allowing animals to better estimate the likelihood that they're going to be able to engage in things without being killed.”11

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