New research shows that some of the ant species in New York City enjoy eating junk food.
Researchers at North Carolina State University tested isotope levels in ants on the streets of Manhattan to determine the makeup of their diet.
“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,” said Dr. Clint Penick, who is the lead author of a paper on the work and a postdoctoral researcher at N.C. State.
“This could also help us determine which species are doing the most to clean up our trash,” Dr. Penick added.
The researchers collected more than 100 ant samples, representing 21 species, at dozens of sites on sidewalks, street medians, and parks in Manhattan. They then analyzed those samples to determine the isotope contents of their bodies.
Carbon-13 is a type of carbon that is associated with grasses such as corn and sugar cane. Corn and refined sugar are present in junk food. Ants that eat a lot of human food have higher levels of carbon-13 than ants that avoid human food.
The study showed the pavement ant, which is the most common ant species on sidewalks and medians, had the highest levels of carbon-13. In general, the species found in medians had higher carbon-13 levels than those species found in parks, according to the researchers. The ants living in closest contact with humans look more like us in terms of their isotope content, Penick says.
“Human foods clearly make up a significant portion of the diet in urban species,” Penick said. “These are the ants eating our garbage, and this may explain why pavement ants are able to achieve such large populations in cities.”
The researchers also found that an ant species, called Lasius cf. emarginatus, and only found in NYC within the past five years, is thriving on Manhattan’s medians. It is one of the few species other than the pavement ants to be found in high numbers on the city’s sidewalks.
However, isotope analysis showed that L. emarginatus has no preference for human food. These ants appear to split their time between subterranean nests and foraging in the branches of trees along NYC streets.
“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 research paper, “Stable isotopes reveal links between human food inputs and urban ant diets,” was published in the journal Proceedings of the Royal Society B.
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