In the words of the great ecologist E. O. Wilson, ants are among the “little things that run the world.” It turns out they even help clean the streets of New York City.
Over a period of six days, a team from North Carolina State University dropped hot dogs, cookies and potato chips around a 150-block section of New York City to study how much food-waste scavengers could eat in 24 hours. They found that arthropods—invertebrates with an exoskeleton, including insects and spiders—act as a rapid trash-clearance service. Pavement ants in particular are voracious consumers of food waste and together with other arthropods are capable of eating up to 6.5 kilograms (about 14 pounds) of waste per block per year. This chomping adds up to 60,000 hotdogs, 200,000 cookies or 600,000 potato chips across Broadway and West Street. The study was published December 2 in Global Change Biology.
The researchers used insect traps to capture 32 different ant species around the city. They found more ant species in parks than in streets—but the ants of the street consumed more food. The important difference, it seems, is the presence of the introduced pavement ant (Tetramorium sp. E), one of the most common urban ant species in America.
The pavement ant is a warrior species, emerging in the spring to fight other ants for the best real estate in battles that frequently leave ant body parts strewn across the sidewalk. They are not fussy eaters: they will converge on any discarded junk food they can get their mandibles on.
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Lead author Elsa Youngsteadt says the pavement ant’s environment might explain its aggressive eating habits. Youngsteadt thinks that the warm, dry conditions on the streets could be “amping up” the ants so that they can “run faster, eat more, and [get] thirstier than in parks, resulting in faster processing of food.”
Jari Niemelä, an urban ecologist with an interest in insects at the University of Helsinki in Finland says the study shows that introduced insect species are not all bad. Some of them, like the pavement ant, are “evidently very beneficial” to humanity, keeping down the numbers of less desirable pests that might spread disease. “Of course,” says Niemelä, “people should avoid dropping food, as this feeds unwanted [vertebrates] such as rats. But it seems that arthropods are able to clean part of the mess.”