Urbanization drives some ants to eat more fast food

Humans are passing down their bad eating habits to ants. According to a new study, some of the ants that scuttle around city streets are chowing down on more sugary, corn-based junk food.

Every year, city-dwellers toss about 250 million tons of food into the trash. This waste is “a massive potential resource for urban animal populations,” researchers write in Proceedings of the Royal Society B.

To find out how urban ants were exploiting this resource, the scientists scoured 12 sidewalks, 12 traffic islands, and eight parks in Manhattan for pavement ants (Tetramorium). Sidewalks had the most garbage and foot traffic, parks had the least, and traffic islands fell somewhere in between. The team also collected other species of ants from traffic islands and parks.

Then the researchers analyzed the chemical makeup of the ants. By studying different types of carbon and nitrogen in the insects, the team could gain insights into the bugs’ diets. For instance, animals that eat more meat tend to have higher levels of the isotope nitrogen-15. And a diet rich in corn and sugarcane is linked to higher levels of the isotope carbon-13.

The results suggested that the more urbanized the habitat, the more fast food the ants were eating, the team reports. However, the relative amounts of meat- and plant-based foods in their diets didn’t seem to change across sites. In other words, the ants “were able to balance the types of foods they consumed… whether they were foraging on natural or human food sources,” the authors write.

The team found different results in other ant species. For instance, yellow-footed ants tended to consume more meat at traffic islands then parks. And a species called Lasius emarginatus, which finds most of its food in trees, appeared to have a similar diet regardless of the type of site.

It’s unclear whether fast food is bad for the ants’ health. The large numbers of pavement ants occupying Manhattan’s sidewalks suggest that the bugs are thriving, but the researchers note that the ants might lack proper nutrients or suffer ill effects from ingesting preservatives. Roberta Kwok | 2 April 2015

Source: Penick, C.A., A.M. Savage, and R.R. Dunn. 2015. Stable isotopes reveal links between human food inputs and urban ant diets. Proceedings of the Royal Society B doi: 10.1098/rspb.2014.2608.

Image © Elliotte Rusty Harold | Shutterstock