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Squirrels, they’re just like us: They have personalities

A juvenile golden-mantled ground squirrel at the Rocky Mountain Biological Laboratory in Colorado. Researcher Jaclyn Aliperti studied golden-mantled ground squirrels to see if they had personalities. (Jaclyn Aliperti)

I’m fairly confident that you have a collection of traits, opinions, quirks and mannerisms that make you uniquely you. In other words, a personality. And that means you have something in common with the golden-mantled ground squirrels of western North America. They have personalities, too.

That may not seem like big news — anyone who’s shared their home with a dog or cat knows they’re all different — but the first rule for scientists who study animals is “Thou shalt not anthropomorphize.”

But animal personality is a growing area of research. And that’s why Jaclyn R. Aliperti spent two summers lugging a large wooden box through the Rocky Mountains. It was a personality test. She called it the arena.

Aliperti is a behavioral ecologist and the lead author of “Bridging animal personality with space use and resource use in a free-ranging population of an a social ground squirrel,” a paper published last year in the journal Animal Behaviour.

Ecologists typically study animals on the population level, Aliperti said. That means studying how a certain species interacts with and within its environment: i.e., all of the squirrels, not just one or two.

“But I've always been interested in the individual,” Aliperti said.

One way to define personality is the consistent display of individualized behavior.

“That means, if I’m really shy today, and I consider myself to be a shy person, I’m probably going to be really shy next month or next year or in three years,” she explained.

While a PhD student at the University of California at Davis, Aliperti conducted research at the Rocky Mountain Biological Laboratory in Colorado, where she studied golden-mantled ground squirrels. They are asocial, meaning they live by themselves.

The squirrels that live around the research center are each tagged so their human observers can tell them apart. Aliperti noticed differences in individual behavior. Some squirrels were extremely active, popping up all over the place. Some were more difficult to observe.

To quantify this behavior, Aliperti employed what’s called an open-field test. This was the arena, a white, rectangular box that she lugged to where the squirrels were.

There were four holes in the floorboard of the arena. The wall at one end slid up to reveal a mirror.

(Video: Jaclyn Aliperti)

Aliperti would catch a squirrel, allow it to settle down in a “waiting room” connected to the arena, then open a door to let it into the testing area. A video camera recorded what happened next, including how active the squirrel was, whether it jumped around the arena and whether it investigated the holes in the floor.

Halfway through the test, the squirrel was exposed to its mirror image.

Golden-mantled ground squirrels aren’t believed to recognize their reflection as themselves. Aliperti was curious to see whether a squirrel went up to the mirror and touched it with its paws or nose. That’s the sort of friendly behavior pups exhibit with their mothers.

“Or,” Aliperti said, “are they facing away from the mirror and avoiding it completely?”

After eight minutes, the squirrel was released.

Aliperti also conducted flight initiation tests, slowly walking toward each squirrel in the wild to see how close she could get.

“It’s a very simple idea: Shyer individuals will flee more quickly,” she said.

When she examined her data, Aliperti found individual squirrels consistently differed in four areas: activity, sociability, boldness and aggressiveness. They had personalities.

But she didn’t stop there.

“The fact that I showed for the first time that golden-mantled ground squirrels exhibit personalities was fun and interesting, but it wasn’t surprising,” Aliperti said.

What’s important to researchers is how a personality might affect an animal’s life.

“In the field of ecology we often tie different traits to what we call fitness,” Aliperti said. “That’s really an individual’s ability to survive and reproduce. In a very general way, that is the — quote unquote — point of life.”

Aliperti found that bolder individuals had larger core areas, the primo part of their range that could be an indicator of a squirrel’s success.

“Then I looked to see if their personality is correlated with access to a resource that has been shown to promote survival in this species,” she said.

That resource is perches: permanent or semi-permanent vantage points such as big rocks or tree stumps. These elevate the squirrels, giving them a better point of view to look for predators.

As she wrote in her paper: “Individuals that scored higher for all four personality traits had more perches in both their home ranges and core areas compared to individuals with lower personality scores.”

“This was a really cool finding, a direct tie between personality and a resource we know helps benefit their fitness,” said Aliperti, who is now a science communications specialist for NatureServe, a conservation nonprofit.

What’s the opposite of anthropomorphizing? Animalorphizing? Whatever it is, I couldn’t help wondering where this left humans. Do shy, careful people have less fitness, ecologically speaking?

Aliperti said her results apply only to golden-mantled ground squirrels. Some squirrel species — the yellow-bellied marmot, for example — have been found to benefit from being less social.

Said Aliperti, “The answer to so many ecological questions is: It depends.”

Tomorrow: Squirrel Week continues with the winners of my annual Squirrel Photography Contest.