Think Your City Mouse Has an Attitude? These Scientists Want to Find Out.

Anna Colliton has lived in her apartment in Pelham Parkway in the Bronx for five years, but she suspects the mice have been there far longer.

They also seem to have an unusual favorite food: the spare packets of ketchup she keeps alongside takeout menus in a kitchen drawer. Even if she hasn’t seen a mouse recently, she said, “if I open that drawer up, it will be full of shredded ketchup packets.”

So when she saw a flier on Reddit that read “We want your mice!,” posted by a team of evolutionary biologists at Drexel University, Ms. Colliton, a musician and visual artist, volunteered.

Mice are commonly used in medical research because of their physiological and genetic similarities to humans. But their evolutionary changes can also be observed over a relatively short period, making them an ideal subject for research into how wild animals adapt to, say, urbanization. The Drexel researchers are studying the effects of urban environments on the evolution of house mice in New York, Philadelphia and Richmond, Va.: relatively old cities, where time and development may have caused differences to accumulate between the mice in each city and those in surrounding areas.

Ms. Colliton was intrigued by the study’s goals; she said she had noticed that “to the extent that pests have culture and personality,” her apartment cohabitants were “extremely bold, noisy mice.”

Behavioral traits may be the most obvious differentiators, but the researchers are also using fecal tests and DNA and microbiome sequencing to compare the animals’ bodies. For example, they anticipate that city mice may be larger than country mice, because of differences in their metabolisms.