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Beaver Island chipmunk research

With fewer predators, chipmunks enjoy island life

CMU grad student finds critters aren’t as vigilant about their safety

Contact: Curt Smith


At Central Michigan University's Biological Station and mesocosm facility on Beaver Island, biologists and students can conduct many kinds of research in a variety of conditions, all at the same time. This is one of three stories about current wildlife studies. The others concern bloody red shrimp, an invasive pest with a foothold in the Great Lakes; and lake whitefish, a struggling species.

For the chipmunks on Michigan's Beaver Island, life's a bit like a class with a substitute teacher: It's easy to slack off and not pay attention.

But for their cousins on the mainland, ceaseless vigilance remains the ticket to staying alive.

Shannon McWaters, a first-year graduate student at CMU, is studying the level of chipmunk watchfulness on and off the island. She's finding the island critters are taking full advantage of the relative dearth of predators such as coyotes, foxes, raccoons, weasels and hawks.

"On the mainland, these are all abundant, McWaters said. "As for the Island, there are a few raccoons and foxes, however, they are in low abundance. The biggest predator up here is assumed to be hawks, but I rarely see them."

 

Chipmunks brazenly race between her feet toward the food sprinkled at her experiment site at the CMU Biological Station on Beaver Island.  A short distance away on Michigan's Lower Peninsula: no way.

"I wouldn't be standing here with chipmunks around me on the mainland," said McWaters, who's from Dorr, Michigan, near Grand Rapids. "They'd be freaked out."

The mainland chipmunks also would have their heads in the air, on guard against natural enemies. There's very little of that posture on the island.

"She wants to answer some fundamental questions about how animals deal with danger," said CMU biology lecturer Wiline Pangle, who is McWaters' advisor.

Data from the chipmunks also can be applied to other small mammals, she said. The animals themselves are a fairly easy species to study.

"We can manipulate the chipmunks' environment easily, but they remain in nature," Pangle said

The chipmunks are just fine for McWaters, whose field is behavioral ecology. They're easier to study than the squirrels she researched as a CMU undergrad, and she finds them adorable.

"I always thought they were cute, but I never expected to work with them," she said.

How it's done

McWaters' setup is pretty simple.  Small sticks, about as thick as a large pencil, are placed vertically in holders placed horizonally along the ground. McWaters changes the stick sizes to alter the chipmunks' ranges of view. Increasing the number of sticks from three to nine adds to the complexity.

Food bits are in the middle.

McWaters records how quickly the chipmunks gain familiarity with the evolving landscape and their level of vigilance — the number of times they scan for predators while going after the snacks.

McWaters found not only that the Beaver Island chipmunks have eased off quite a bit, but that they've actually become quite chummy.

She's even named them.

First there's Christy. McWaters jokingly calls Christy her "alpha chipmunk." She's "very, very aggressive" with her food and is always there for research. In fact, her frequent trips to the buffet sometimes ruin the other chipmunks' trials.

Diamond is usually off to the side, bobbing his tail. He's a little afraid but a reliable guest.

Eliza is very timid, stuffing her cheek pouches with goodies and running off.

"I feel like a crazy woman when I talk to them too much," McWaters said, smiling.

There are many others, so McWaters has to keep tabs on who lives in which burrow to avoid checking the same animal over and over.

That's easy on the island. On the mainland, the skittish creatures usually flee to an emergency hiding place, not their personal digs.

"Here it took me about 10 minutes to find a burrow," McWaters said. "On the mainland it took me an hour."

The big picture

McWaters said the chipmunk data can be used in broader research, especially in real-life situations when predators vanish and are later reintroduced.  Hunting bans come and go in Michigan, and ecological equilibrium shifts.

When predators return, will the prey's population crash or adapt with an uptick in vigilance behavior? McWaters wants to find out.

Pangle said about $5,000 from the College of Science and Engineering covers roughly 80 percent of McWaters' project. Grants pay for the rest.

McWaters said her favorite part of the research is when she and the chipmunks are off the clock.

"I think the most fun is when I'm not doing trials," she said. "They will just come up and eat off my lap. It's really cute."


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