UM Researchers Chased Squirrels on Campus With a Remote-Controlled Cat, for Science

McRae used this cat on wheels to chase squirrels on UM's campus, all in the name of science.
McRae used this cat on wheels to chase squirrels on UM's campus, all in the name of science.
Courtesy of Thaddeus McRae

Listen up, kids. Next time you think science is boring, consider how Thaddeus McRae spent two years of his life: namely, chasing squirrels around the University of Miami campus with a remote-controlled cat on wheels and gliders painted to look like hawks.

"We had some very interesting interactions," McRae tells Riptide. "We had people come up and ask, 'What are you staring at through the telescope? An endangered animal?' When we told them we were watching squirrels, they'd slowly back away."

Don't worry -- McRae is not simply a better-equipped version of the old lady who obsessively feeds arboreal rodents.

In fact, his research led to a recently published paper in the scientific journal Behavior with a surprising conclusion: Your average urban squirrel uses a complex combination of squeaks and tail movements depending on specific threats coming in from air or land.

As a kid wandering around forests in his native Michigan, McRae became fascinated with how animals interacted and turned that obsession into a scientific career in behavioral ecology.

He moved to Miami in 2005 to study at UM and planned a research project in Kenya for his doctoral thesis. But when a violent election conflict erupted in Nairobi in 2007, he had to come up with a new game plan.

That's when he brainstormed with Steven Green, his doctoral mentor at UM: Why not study the army of squirrels right on campus? "It had some big advantages as an urban system," McRae says. "For one thing, the squirrels are already habituated to humans, so you don't have to control that factor."

McRae wanted to answer a simple question: Do squirrels use different signals depending upon different types of threats? To find out, he and Green cooked up an ingenious study.

First, they built a life-like cat on remote-controlled wheels and painted some gliders to look like hawks. Then they sicced the fake predators on the campus squirrels and recorded how they reacted. (As a control, they mounted a red ball on wheels and ran it at the squirrels to elicit a more general alarm sound.)

The cat, hawk and ball set-ups McRae and Green used for their research
The cat, hawk and ball set-ups McRae and Green used for their research
Courtesy of Thaddeus McRae

Turns out the critters have three distinct warning sounds: the "kuk," a short bark; the "quaa," a longer squeal; and the "moan," a whistling sound. They also twitch their tails in regularly repeated patterns.

From the reams of data they collected, McRae and Green found a strong correlation between some of the sounds and tail movements and the type of predator.

"Whereas previous studies did a lot of work with vocalization in species, this one also used the tail signals," McRae says. "By looking at them together, you can much more accurately predict the type of predator."

What the scientists don't know yet is the purpose of the complex signals: Are they meant to warn other squirrels whether to flee up a tree away from cats or down to escape hawks? Or do the specific sounds scare off specific predators?

McRae is already planning a follow-up study on campus to find out. So if you're in Coral Gables and see a robotic cat zipping toward some frantic squirrels, don't freak out.

"I did get some really funny looks at the remote-controlled cat," he says. "I had to reassure [people] it was not a real cat strapped to a remote-controlled car."

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