How do people affect their rodent neighbors? One southern Illinois scientist wants to find out
On a humid, mid-April morning, nearly a dozen students were scattered around a small field across the street from Southern Illinois University, Edwardsville. They planted pink flags, strung measuring tape up and down the field and used machetes to clear their way through tall, prickly prairie grasses.
“Did I tell you about the fox? A fox just ran past Danielle’s foot. Like, really!” exclaimed their professor, Danielle Lee, an animal biologist at SIUE.
The fox sighting is important, as Lee and her students are trying to find out what rodents and other animals live near the campus. Lee and other scientists who study urban ecology are just starting to discover the ways in which human development affects wildlife.
Research has shown, for example, that artificial lighting at night disrupts internal clocks in birds, which causes them to sing earlier in the morning and even hurts their reproductive development.
“I’m curious to know if that’s happening in mammals,” Lee said. “We do know that they’ll alter their behaviors so that they’re active at night, or [they live] in places where people don’t spend that much time, like cemeteries and parks.”
She wants to study differences in how rodents behave to gain insight to how living near people cause them stress.
“I’m hoping to see a variety of field mice,” Lee said, “So like peromyscus, deer mice. I’d like to catch some voles. House mice are very possible. We’re in between two dorms.”
Lee’s also studied rodents in Tanzania, namely the African giant pouched rat, the largest rats in the world. People there told her that the species was sheltering in local sewers.
“They build burrows in nature, so [I’m] looking at how they adjust and use our development for their own purposes,” she said. “Maybe they’re not building burrows, but they’re using the sewer system like a burrow system. We know that as animals become more accustomed to urban areas, they innovate.”
Once Lee has a sense of what wildlife lives around SIUE, she will trap rodents and run tests on them to study their behaviors. One such test will involve providing a wheel for the rats, mice, voles or whatever she catches to see, for example, how long it takes for them to interact with it and whether or not they choose to run in it. Those tests will begin later this summer.
Trapping wild rodents takes time and patience
In the field, Lee’s class set up what grid that measures 100 meters by 40 meters. Along specific points within the grid, she and the students put down Sherman traps, small metal boxes that are designed to catch small mammals.
The next morning, she and an undergraduate student, Jacquelyn Isom, wake up early to check the traps. Isom made the first finding that morning and handed the metal box to Lee.
“I’m just going to take a quick peek,” Lee said, carefully opening the trap door.
She gasped. “It’s a peromyscus,” she said. “They’re my favorite because they’re so cute.”
The second and last specimen they find that morning is a prairie vole. Both of the traps are brought into a spot in the shade. Lee put on latex gloves and took out the one containing the vole. She gripped the fur on the back of the vole so that its belly faced out. It’s so small that it can fit easily in the palm of her hand.
She hands Isom a book to classify the animal.
“I know what it is, but she needs to learn,” Lee said.
Isom flipped through the pages. “Distinguishing features," she read, "large head, heavy-bodied, short-tailed mice…”
“Yep, yep,” Lee nodded, as she examined the vole to determine its sex. “I would say he’s a subadult male, trying to find his place in the world.”
Then, they looked at the deer mouse.
“Wow, she has a long clitoris!” Lee said. Then she paused and corrected herself. “Actually, I think it’s an immature male.”
After they finished taking notes, they returned the traps to their original locations and released the rodents back into the wild.
“It’d be nice if I was catching them all the time. Then I go, OK, I’ve got a good population where I can do some behavior studies,” Lee said. “I think we have more [animals] than we think. They’re just good at staying out of our way.”
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