City Mice Get Tougher Faster, Geneticists Say

Should country mice visit their cousins more often? DNA suggests city mice are rapidly evolving to resist disease and heavy metals.

Huddled together in the wooded “islands” of New York City parks, urban white-footed mice have begun to differentiate genetically from their rural brethren in the larger forested areas surrounding the city—and from one another within the metropolis—according to new research. Two different genetic models “identified most city parks as harboring unique evolutionary populations” of the woodland rodents, with just a few green areas like cemeteries and highway medians permitting limited migration, writes lead researcher Jason Munshi-South, Ph.D., of Baruch College, City University of New York.

The “urban adapter” mice share a few characteristics that distinguish them from rural mice—differences in genetic makeup that would likely affect their ability to metabolize toxic substances, resist infection, and fend off gene mutations that might lead to cancer. These genetic differences appear to have evolved independently in the mice of each park—and to have done so with surprising speed, in 200 years or less.

Munshi-South’s research team is now working to identify the pressures over the last two centuries that produced the adaptations, to help them better understand the effects of urbanization on native species.