Where the Wild Things Are
There aren’t many places at Fordham where the view outside your office window is the skull of a deer whose carcass you observed getting ravaged by predators and absorbed back into the ecosystem.
Then again, Jason Munshi-South, Ph.D., never wanted to be confined to a laboratory. Munshi-South, an associate professor of biological sciences at the Louis Calder Center Biological Field Station in Armonk, N.Y., studies the ways in which human development influences the movements of wildlife, and, if that movement has been impeded, how their evolution is altered as a result.
Places like Van Cortlandt Park in the Bronx and Highland Park in Manhattan offer significant refuge for native mammals and amphibians, even though barriers such as roads, rivers, and buildings hem the animals in, he said.
“Think of the New York City parks as a series of islands that are potentially isolated from each other, and thus are these replicated experiments where these populations just change from generation to generation,” Munshi-South said.
In one of his first experiments, Munshi-South, who came to Fordham last year, supervised the trapping and genetic sampling of 20 to 25 white-footed mice at 14 city parks. The mice are native to the area and plentiful, so he figured that if an important common species could move around the area, then maybe other species could too.
“You could basically tell one park’s mice apart from another, just based on a small number of positions in their genome. They were actually quite a bit more isolated than we’d thought, and they’ve probably just been diverging slowly from each other for the past 100 years or so, or maybe even longer in some cases,” he said.
Where there was obvious migration of genes between “islands,” Munshi-South found corresponding levels of green cover such as shrubs and high grass that let the mice travel undetected. It turns out that long linear parklands, cemeteries with unmowed grass along the edges, and tributaries like the Bronx River that are lined with trees, shrubs and tall grasses are perfect paths for the animals to travel.
When they can’t travel, animals change ever so slightly through microevolution. These don’t necessarily affect biological functioning but they do show up under the microscope, he said. He has documented two small populations of salamanders in Highbridge Park that have been separated long enough to have grown to be biologically distinct.
A grant from the National Institutes of Health will enable Munshi-South to look at differences among white-footed mice in rural, suburban, and urban environments. A mouse in the city might be exposed to more pollution, whereas a mouse in the suburbs has to adapt to the fact that deer have eaten most of the underbrush they might have otherwise climbed and hopped over.
“The idea is to look at how urbanization influences the variation these animals have in their genome,” Munshi-South said.
“The question is, with the way we’re modifying the landscape, are we creating pockets with less or different variations that may influence how they evolve in the future?”
One of Munshi-South’s projects involves tracking the movements of stream salamanders on Staten Island, at the Calder Center, and in the Catskills. Like frogs, salamanders are proverbial canaries in a coal mine because they’re highly sensitive to pollution. Restore their populations, the logic goes, and other species will follow.
And then, because this is New York City, there are rats. Munshi-South is supervising the capture of Norway rats from every zip code in Manhattan so he can study how they’re related and build models showing how they move around the city. His preliminary data shows they cluster locally, much like people who stay relatively close to their neighborhoods.
“If you look at rats in a small number of parks in lower Manhattan, or from a certain train station or a certain housing project, you see a local colonial structure,” he said.
In addition to looking at how New York rats use subway tunnels and sewers to move around, Munshi-South is collaborating with 15 labs around the world to track the movement of Norway rats across the globe, from Mongolia and Northern China, where they originate, to Europe in the 1500s and to the United States around 1750.
Educating the public on the wildlife in its midst is important not only for better preservation efforts, but also because the New York metropolitan area is being repopulated by species that were nearly wiped out hundreds of years ago. Wolves, coyotes, bears, beavers—all are attracted to the same forest edges that white-footed mice like, and are all natives to the area.
“All things considered, people would like to have greener cities, with networks of green spaces. Not really wilderness, but a kind of novel, urban type of habitat that people can use, and nature will sort of follow along,” he said.
“We should accommodate wildlife rather than just live either in ignorance or in antagonistic relationships, where we try to keep them out.
“Because, long-term, that’s just a losing strategy.”