Rodents Thrive Near Highways

Dale Sparks, associate professor and research scientist in the department of ecology and organismal biology, and a team of students are evaluating the quality of Interstate 70 as a small mammal habitat from the Indiana state line to Marshall, Ill., with the permission of the Illinois Department of Transportation.

“Biologists have often considered roadways as useless or worse for wildlife,” Sparks said. “The traditional view is that these areas are too badly damaged to serve as effective habitat. However, any birdwatcher and many bored drivers know that hawks spend a lot of time sitting on the roadside staring at the ditches, medians and highway triangles, so there must be something out there.”

Previous studies in Kansas have shown highway triangles have a different mammal community than the surrounding landscapes, including high densities of one mouse considered rare. A student in northwest Indiana set up traps in a few triangles and caught deer mice considered extinct in the Chicago area.

“All those scattered reports convinced me that we should take a closer look at highways as habitat for small animals,” Sparks said about obtaining support from the Indiana Academy of Science.

It is an in-depth study that hasn’t been done before, according to ecology doctoral student Justin St. Juliana of Wheaton, Ill.

“Medians are considered junk habitat,” he said. “That’s not necessarily been confirmed. We’re finding a pretty good community of rodent species, a variety.”

Just like the hawks, Sparks said they are finding mice and other rodents that call the medians, triangles and roadsides home.

“Everything in the preliminary data says medians are great habitats,” Sparks said.

On the roadsides and in the triangles, they have found white-footed mice, deer mice and voles. In the medians, they have found white-footed mice, deer mice and shrews, including one type of shrew that is on the Indiana watch list. That same shrew is not on the Illinois watch list where the crew is working.

“Certainly from the preliminary data, it’s a denser, more diverse community in the median than the triangles and ditches,” he said.

Senior biology major Gabriella Gonzalez-Olimon from Baja California, Mexico, called the project interesting.

“Before doing this, I didn’t even imagine what could be on the roadsides,” she said. “Letting the people know what’s there is fun for me. It’s not as simple as it looks out there.”

The biology major said she has enjoyed being on the roadsides, setting traps for the animals and putting out feeding trays.

“You learn a lot more things by doing it than by listening to a teacher,” she said. “You really have to apply everything you know.”

The team traps the small mammals before marking and releasing them in order to estimate populations. Also, they set out feeding trays of seeds mixed with sand.

“Mice that have no fear of predation can spend all night digging up each seed,” Sparks said. “Scared mice, conversely, eat very little of the seed and soon leave. We can get an estimate of the habitat quality by seeing how much seed the mice leave behind.”