Urban Ants Prefer Junk Food Over Natural Sources

Experts have long known that, just like humans, not all ants are created equal. Even colonies of the same species may have different collective personalities depending on where their nest is. Now a new study has found that ants living in urban environments have learned to prefer junk food far more than their rural counterparts.

"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," Clint Penick, a postdoctoral researcher at North Carolina State University explained in a recent statement. "This could also help us determine which species are doing the most to clean up our trash."

Penick and his colleagues collected more than 100 ants samples, representing 21 ant species in all. The samples came from a large variety of environments including sidewalks, street medians, and parks in Manhattan, NY. The researchers then closely analyzed the isotopes within each ant's body to help them determine the nature of their average diet.

They specifically were looking for traces of carbon-13, which is commonly associated with corn and sugar cane products. Both the ingredients are practically everywhere in human food, meaning that if an ant has learned to live off human food, as opposed to natural resources, it will have higher carbon-13 concentrations in its body.

As expected, the researchers found that common pavement ants (IE -Tetramorium caespitum), who have been living alongside human urbanites for as long as cities have existed have a clear preference for human food, boasting high concentrations of carbon-13.

He told the Associated Press that this preference may have given them a completive advantage, as pavement ants easily outnumber most other species in the city.

"Humans bring a ton of general resources," he said. "The species that can take advantage of these resources the best, sort of wins."

However, the study goes on to show that not all urban ants are junk food specialists.

Lasius cf. emarginatus, a species of ant that has been thriving in Manhattan's street medians, was also commonly found in high numbers all over the city's sidewalks. And despite this, they did not have carbon-13 concentrations anywhere near those of T. caespitum. Instead, they seem to split their time evenly between collecting human garbage and the few natural resources the concrete jungle offers.

"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," Penick said.

The results were recently published in the Proceedings of the Royal Society B.

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