Miniature Russian spyware is infiltrating an underground Canadian community.

The perpetrators? Scientists studying how eastern chipmunks communicate. For the first time, the team has outfitted the little striped animals with collars bearing inch-long (2.8 centimeters) microphones, the world's smallest digital recording device, according to Guinness World Records.

Using these espionage tools, the team recorded, analyzed, and decoded constant chipmunk chatter, instead of relying on static microphones that had previously limited scientists in understanding the secret lives of wildlife.  

So far, the hardy microphones, deployed on chipmunks in southern Quebec's Green Mountains Nature Reserve, have provided unprecedented data on how and when chipmunks call, which is helping reveal the burrowing rodents' individual personalities.

"What I'm really interested in is individual differences in vocal signals and other behaviors," says Charline Couchoux, a biology Ph.D. student at the University of Quebec in Montreal and a National Geographic Young Explorer.

For example, Couchoux, who published her chipmunk research in May in the journal Scientific Reports, is curious to know whether personality traits such as boldness are hardwired.

Her recordings of 21 chipmunks have also captured the animals' resting heart rates, which can indicate how they react under stress; whining from baby chipmunks in the burrow, which can show how they care for their young; and how much they scratch themselves, which can tell scientists how many parasites they have.

"Just as Cool as Monkeys"

After luring the chipmunks into peanut butter-smeared cages, Couchoux slips tiny microphone collars around their necks and releases them back into the wild, where she listens and observes them from a close range. Each chipmunk wears a different colored ear tag so she can tell who's who.

Along with watching their natural behavior, Couchoux also replicate threats. To simulate an aerial predator such as an eagle, Couchoux tosses a hat over them, causing them to emit an alarm called "chucking," a low-frequency, repetitive sound.

The research shows that chipmunks will "chip-trill" (a high-pitched staccato) while defending their territories, "chip" (a high-frequency alarm) when facing a terrestrial predator, and "trill" (a variation of chip-trill) when they are pursued or surprised by a predator. Some chipmunks mix and match these calls or use them in unusual ways, Couchoux says.

"There are so many different structures of calls, so it's interesting to try to understand what call is for what purpose," says Jeanne Clermont, Couchoux’s assistant and a student at McGill University.

Daniel Weary, professor of animal welfare at the University of British Columbia who's studied mammal vocalizations, says these microphones give us a different view into the chipmunks’ world.

Capturing 24-hour vocalizations in underground environments provides "a much more nuanced view of how they interact," says Weary, who was not involved in the microphone research.

While scientists have confirmed that species such as vervet monkeys and songbirds have complex ways of communicating, little research has been done on chipmunks. Studying animal calls and sounds is helping scientists discover how vocalization evolved over time.

"The humble chipmunk that's around us all the time are doing just as cool things as monkeys," Weary says. "It's possible that this kind of data will allow us to separate animals in ways that we couldn't have anticipated earlier."

Chipmunk Personalities: Bold vs. Shy

Analyzing the various calls has also given Couchoux an insight into their personalities—for example, the animals she's studied seem to be either bold or shy, she says.

Among the microphone-wearing chipmunks, the bold ones will only emit an alarm when a predation risk is real. They're also more aggressive during a territorial fight with other chipmunks, emitting more calls to display dominance. Although chipmunks closer to their burrows are supposed to win territorial fights, Couchoux sees bold individuals win no matter what.

A shy chipmunk, Couchoux says, is more likely to call when there's a false predator, such as a falling leaf or gust of wind. But during a fight, they keep quiet.

Sensing Danger

There's more to come, too. This summer, in the southern Quebec deciduous forest, Couchoux will test if her group of chipmunks can pick out a trustworthy caller from one that cries wolf.

For instance, the group might not pay attention if they hear a shy chipmunk and seek refuge if they hear a bold one. Knowing which animal is right is an important time-saving tool.

"If your neighbor keeps emitting calls and you stop foraging to listen, you lose time to do other activities and gain resources," Couchoux says.

If this holds true, the results will be the first to show that chipmunks, like songbirds, can differentiate their neighbors' calls.

"These are very smart animals," Weary says, "that are sensitive to the animal behaviors around them."

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