Jason Munshi-South has spent the last four years trapping, weighing and measuring New York City mice. Not those house mice that arrived in the city on ships with the European settlers. Munshi-South studies white-footed mice. They live in forests throughout the Northeast, including parks dotting the city’s landscape.
An assistant professor at Baruch College and an evolutionary biologist, he is looking at how white-footed mice, which arrived in the region 15,000 years ago after the ice glaciers retreated, are adapting to life in the metropolis.
“They’re cute, have big eyes and big whiskers,” says Munshi-South. “You find more of them in city parks than even upstate New York and that makes them a useful model for research. They’re a natural part of the urban ecosystem.”
Munshi-South and his colleagues take small clips of tissue from ears and tails, so they can analyze the DNA of the mice. White-footed mice are predisposed to survive in urban environments, but Munshi-South wants to know whether they’re adapting further so they can thrive even easier in the human-dominated world.
Usually, he says, when a species is trapped in a small area — the way the mice are trapped in parks that are like small islands in a sea of concrete — over time they will lose the unique differences between the individuals and become more alike. He was astonished to learn that white-footed mice in each park still are genetically distinct from each other and how great the differences remain between mice in different parks.
“That was very striking,” he says. “We thought that not enough time had passed for those differences to be that severe, that there would be more movement of mice throughout the city.”
Munshi-South began his urban wildlife research career as an undergrad researcher studying monk parakeets in Chicago. He switched gears later and was trained as a tropical biologist. For a while, he tracked elephants in Central Africa, to see how they were impacted by oil fields, and studied the evolution of proboscis monkeys on the island of Borneo. When hired at Baruch, he wanted to stay local.
“Once you’re a professor it’s very hard to go away for four or five months at a time to these very remote locations,” says Munshi-South, who’s also monitoring the spread of coyotes in the city, particularly in the Bronx and Queens and studying stream salamanders that are concentrated on Staten Island. “And I realized that there’s all this native wildlife in New York City living within the five boroughs that I had no idea about. It’s an excellent study system for looking at evolutionary biology because you have animals that are confined to one place, that are stuck in island situations.”
Currently, Munshi-South is working on identifying specific genes in mice that have changed due to natural selection from living in the city. It’s an ongoing project but he says he has already identified genes that have to do with immunity, specifically dealing with heavy metals and pollution.
“We have a lot of lead in parks,” he says. “A few parks were used as ash dumps when New Yorkers used coal as a source of heat. Mice in those parks may have mutations in genes that can remove heavy metals from the body or at least resist the damage from heavy metals.”
The mice may also hold a key to how humans have adapted to city conditions. White-footed mice are closely related to the mice used for lab research, the main model for human health research, “so if we can understand what’s happening to mice living in the city, we might have some leads on how urban life affects humans, especially with things like pollution,” he says.
With more than 50 percent of the people in the world living in cities, it only makes sense to study how humans and how animals experience these urbanized and suburbanized environments.
“There’s no longer this divide between the wild and the city,” says Munshi-South. “This is our urbanized world now and we need to understand how nature works in cities.”
Last summer, Munshi-South expanded his research to forests in upstate New York, so he could analyze how these mice are changing compared to their rural ancestors. He received a $200,000 grant in September 2012 from the National Institutes of Health to continue the research he started four years ago.
For his next project, Munshi-South is thinking about urban creatures that aren’t as cute as mice — rats. “We’re a bit resistant to do this research,” he says, “because rats are not pleasant to work with, but we think they’re an important part of the ecosystem and no one really knows anything about the evolutionary biology of rats in New York City.”