NYC traffic islands like little Galapagos

The white-footed mouse, Peromyscus leucopus, has evolved to live in NYC. photo by Roger W. Barbour

New York City’s tiny traffic islands and parks are like a little Galapagos chain, with their isolation fostering diverging evolutionary traits, says a New York Times Science Section story. Carl Zimmer’s story looks at a bunch of new research that, instead of looking at cities as wastelands, recognizes that they are fantastic grounds for studying evolution because the isolation and pressures from people, traffic and pollution force species to adapt or die out.

Because the parks and islands in New York are so cut off from each other by pavement and buildings, they are effectively islands. New Yorkers are often surprised how deftly some animals travel from one area to another. Coyotes and chipmunks take rail lines into the city. Deer swim the waterways. Pigeons and squirrels have been know to hitch rides on public transportation. But urban wildlife is often cut off from breeding with its country cousins.

The serious research going on around New York compares native and invasive ant species on traffic islands. Jason Munshi-South studies genetic traits of white-footed mice found in the city (resistant to toxins) but not in nearby woods. “The amount of differences you see among populations of mice in the same borough is similar to what you’d see across the whole southeastern United States,” he said. Isaac I. Wirgin of New York University Medical Center found that tomcods around a PCB site on the Hudson died off except those that developed an immunity to the toxin. A worm near West Point developed a way to block cadmium, but now that the mess has been cleaned up, the trait is melting away.

I’ve often wondered about city squirrels. It could be more of a behavioral or cultural adaptation, but they do remarkably well here. That’s why I’m always reluctant to release the squirrels I raise as a wildlife rehabilitator anywhere but the city. (Many think they’d rather live in the remote woods, away from people.) I figure these city squirrels have been evolving for 100 generations or more to live with people in the city. Who knows what would happen to them if they got thrown in a more natural environment that is totally unnatural to them?