New research from North Carolina State University examined the ant species of Manhattan in an effort to determine what they eat. The aim of the research was to find out why certain ants thrive in urban environments while others move to the outskirts.

Some of the results, however, were very surprising.

“We wanted to learn more about why some ant species are able to live alongside us, on sidewalks or in buildings, while other species stay on the outskirts of human development. This could also help us determine which species are doing the most to clean up our trash,” said Dr. Clint Penick in a statement.

Penick is the lead author of the paper “Stable isotopes reveal links between human food inputs and urban ant diets” in Proceedings of the Royal Society B and a postdoctoral researcher at NC State.

Researchers collected 21 different species of ants from Manhattan parks, sidewalks and street medians. Over 100 samples were analyzed to determine the presence of the carbon-13 isotope of their bodies.

Carbon-13 which is also used for carbon dating is associated with human food because of its presence in grasses such as sugar cane and corn. Because it is present in nearly everything humans eat from processed foot to hamburgers, ants that eat a lot of human food have higher than normal levels of carbon-13 in their systems.

It was no great surprise that the most common “pavement ant” species (Tetramorium Sp. E) had the highest carbon-13 levels. In general species found on sidewalks and in medians had higher levels of carbon-13 than those found in parks. In other words, the ants that lived most closely with humans were most like us in isotope content, according to Penick.

“Human foods clearly make up a significant portion of the diet in urban species. These are the ants eating our garbage, and this may explain why pavement ants are able to achieve such large populations in cities,” he said.

There is, however, a glaring and fascinating exception to the rule. The species Lasius cf. emarginatus which has only been found in the last five years in New York City does not seem to be reliant on human food for its diet at all.

Although the species are thriving in the medians of Manhattan’s roadways, but showed almost no carbon-13. According to the researchers, the ants appear to divide their time between subterranean nests and the trees that line the streets of New York.

“This highlights the complex nature of urban ecosystems and how much we still have to learn about how these species relate to each other and to the environment,” said Penick.

When people think of ecosystems, they tend to think of rainforests and wetlands. However, in recent years, there has been an increased interest in the ecosystems of urban environments where the vast majority of the human population lives.

In late March, a Los Angeles biological survey study revealed the presence of 30 new species of fly gathered from 30 different traps across the LA area.