Drop a cookie or ice cream cone on the sidewalk, wait a few minutes, and you’ll probably meet a few pavement ants–the unofficial street cleaning crew of the insect world. A new study suggests that the particular species of ant thrives in cities because it eats so much junk food.
“There are over 40 species of ants in Manhattan, which is a pretty big number,” says Clint Penick, lead author of the study and a postdoctoral researcher at North Carolina State University. “But most are found in parks like Central Park. There’s one species that dominates the sidewalks: The pavement ant.”
The researchers wondered what makes some ants better at urban life. Their hypothesis? Food. “It turns out nobody had been looking at what animals are eating in cities, at least in any city the size of New York,” Penick says.
Penick wandered up and down street medians on Broadway with an aspirator, a bong-like gadget that researchers use to collect ants by sucking through a tube. “Essentially, I went around New York, walking around the sidewalks on Broadway, crouching down and huffing ants off the sidewalk with this weird little device,” he says. (He says he didn’t get any strange looks).
Back at the lab, the researchers analyzed the ants’ carbon isotopes and nitrogen to figure out what they’d been eating, the same type of test that is sometimes done on human hair. The test can show types of food that are based on grasses like corn or sugar cane–so it’s good at picking up junk food.
“In standard fast food meal you have a hamburger that’s corn-fed beef, you have a soft drink that’s sweetened by corn syrup or sugar cane, and even French fries are often fried in corn oil,” says Penick. “Everything that you’re eating, fast food wise, has a signature of corn…you can actually take a hair sample from someone in Manhattan and someone in London and tell who’s living in North America because of the corn signature in their isotopes.”
Like New York humans, New York pavement ants clearly eat junk food–but the other ant species around the city don’t eat as much. The researchers think that the species may be better adapted to eating human food, and maybe also better at finding cookie crumbs and telling the rest of their colonies quickly.
The same thing probably happens with other types of animals that thrive in cities. “The pavement ant is like the ant version of a pigeon,” he says. “It’s a species that tends to follow humans around. So we’d think that there’s something going on with pigeons, something going on with house sparrows that are also spread across cities, certainly rats.” The researchers are now studying honeybees, another species that lives in close contact with humans.
As cities continue to grow, certain species, like the pavement ant, probably have a better chance of survival than others. Penick hopes that the research reminds people that the ants are good to have around, and points back to a colleague’s research revealing that ants in a small area on Broadway collectively cleaned up over 2,000 pounds of human food off sidewalks in a year.
“Every hot dog that an ant eats is something that’s not there for a rat,” he says. “So I think everyone can agree that having ants in the city is better than having rats in the city. I think there’s an upside to understanding what’s going on here, and what species are helping us keep our city clean.”