A study at Webster University has revealed that Monsanto's weed killer Roundup can significantly change ant behavior.
Researchers began two years ago to study how ants are affected by man-made contaminants, including Roundup. The product has become controversial recently due to allegations that its key ingredient, glyphosate, causes cancer in humans.
The ant study hasn't been published yet, but student researchers noted that the herbicide significantly affected western harvester ants.
"When we put Roundup in the habitat, all digging ceased. I was dumbfounded. I didn't believe it," said Victoria Brown-Kennerly, a geneticist at Webster University who supervised the project. "These chemicals are not lethal to the animals, but it's definitely changing their behaviors."
Western harvester ants, often used in ant farms, are known to create underground tunnels.
"These underground tunnels are really a part of the life cycle of the ants," Brown-Kennerly said. "This is where the eggs are lain by the queen, where the larvae are tended to by the workers. This is where they take their seeds down, where they have their food stored."
The students also found that Roundup's key ingredient glyphosate was not responsible for causing the ants to stop digging.
"Roundup is a really complex mixture of at least five different chemicals," Brown-Kennerly said. "I had a student who went in and de-convoluted this thing and looked at every chemical and we figured out it isn't glyphosate."
She added that her laboratory is looking into how different environments, such as gel, sand or soil, can affect exposure and behavior changes in ants.
"There's been studies with Roundup that show that it's not lethal but that's where the studies end," said Krystal Meza, a recent graduate of Webster who worked on the study. "But it's causing these abnormalities that people don't pay attention to. So how does that affect ant colonies in the long run?"
But the herbicide's effect on ants could be different out in nature than in the lab, said Clint Penick, an ant researcher at North Carolina State University who is not involved with the study.
"The question is how much of Roundup, how much of these chemicals are making it into the soil and how saturated is the soil with these compounds?" Penick said. "If it's only in the first centimeter of topsoil and the ants dig through that pretty quickly, then it might not have a major effect on them in nature, whereas if you have a fully saturated soil in the lab, you might see stronger effects."
He added that the Webster study is an interesting "first step" to learning how chemicals in common household products affect ants and our environment.
"Ants turn the same amount of soil as earthworms," Penick said. "So if you have ants in the garden, they can actually help benefit the plants. So you wouldn't want to be putting chemicals that could potentially harm the species that help your soil health. We have a bunch of household chemicals that could have potential negative effects on ecosystems and especially if you're trying to protect native species, such as pollinators and ants, it's a good idea to understand the health risks for the environment."
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