A new study published in the journal Urban Ecosystems has revealed that the common black garden ant (Lasius niger) behaves differently depending on whether it lives in a bustling city or the quiet countryside. The researchers, led by an international team from Ukraine, Germany, and Poland, found that urban ants are much more willing to accept low-concentration sugar solutions, which their rural counterparts typically reject. These findings suggest that the pressures of city living may be fundamentally altering their nutritional landscape.

The research focused on how urbanization – one of the most extreme forms of land-use transformation – affects the food choice of insects. By offering sugar solutions of varying concentrations to ants on active foraging trails in both urban and rural settings, the team discovered that urban populations showed a significantly higher acceptance of all sucrose levels, with the difference being most pronounced at the lowest concentrations. In other words, city ants were significantly more willing to accept the low-concentrate solutions than their rural counterparts. The study suggests that environmental stressors such as the “urban heat island” effect, microplastics, and soil pollution may affect nutrient absorption in urban plants. This, in turn, may reduce the quantity and nutritional quality of the primary food source for Lasius niger, namely the honeydew produced by aphids.

“While pollinator insects such as bees are often the focus of urbanization studies, ants are somewhat neglected,” says Stanislav Stukalyuk, the study’s first author (Institute for Evolutionary Ecology, National Academy of Sciences of Ukraine). “This overlooks a major aspect of urban ecology: The ant we studied is probably the most common ant in Europe, and there are almost certainly more of them than any one pollinator species.”

Tomer J. Czaczkes, corresponding author (Freie Universität Berlin), notes that the ants’ behavior reflects their past experiences. “Ants are essentially comparing what we give them to what they usually find in their environment,” he explains. “Urban ants may be accustomed to lower-quality, ‘dilute’ resources from stressed city vegetation. When they are offered a drop of dilute sugar solution, they are happy to take it. But rural ants were essentially ‘disappointed’ with the offering, and turn up their nose (or antennae) at it.”

While the study focused on the behavior of a single species, the findings hint at a potential new way to monitor the general health of urban ecosystems. Because ants are sensitive to environmental changes and display rapid behavioral responses to habitat quality, tracking their “pickiness” could theoretically serve as a subtle indicator of the stress levels within the wider biological community.

However, Gema Trigos-Peral, last author of the study (Museum and Institute of Zoology, Polish Academy of Sciences), urges caution: “This is just the first step. We still do not understand the causal links that lead from urban ecosystems to this shift in ants to not being picky. It could reflect stressed trees, but it could also reflect stressed ants, or several other things. There is still lots to be done!”

However, the researchers are excited about the potential of their study. “The method we developed is quick, easy, and fun. It could easily be deployed by citizen scientists and the general public to understand our environment better. Even school classes could run such experiments!” says Czaczkes.

According to the researchers, the study’s findings underscore the urgent need to understand how urban ecosystems function in order to better inform conservation strategies as cities continue to expand globally.