What is this, a toilet for ants? Yes, Derek, it is! Researchers working with black garden ants reveal that these hard workers form well-defined fecal patches inside of their nest -- a behavior that’s never been documented in ants before. The findings were published in PLOS ONE this week.
Social insects have multiple strategies for dealing with poop and other waste matter. Honey bees perform defecation flights, spider mites dump their feces outside their silk shelters, and some ants make special waste-storage chambers (called kitchen middens). Sometimes, the insects even put the waste to use, as construction material or a defensive shield -- suggesting how feces and refuse may not always be hazardous waste.
In previous work with ants, Tomer Czaczkes from Universität Regensburg had noticed little dark patches in the corners of their nests. “I knew what they looked like to me, but you can’t just go ahead and say, ‘Well, it’s brown, it must be a toilet,’” he tells the Los Angeles Times. And it was surprisingly hard to catch ants in the act. So, “we did the experiment,” he adds, “to see what really is going on.”
His team housed 21 small colonies of common black ants, Lasius niger, in plaster nests and provided them with a sugar solution that was colored either red or blue so they could see where the ants defecated. After two months, between one to four well-defined red or blue patches formed within each of the plaster nests, especially at the corners. The dark patches matched the color of the sugar solution they were fed.
To the right you can see the plaster nests that had been inhabited by 150 to 300 workers ants for two months.
These colored patches never contained other waste material, like uneaten food or the corpses of fallen nest-mates -- these were collected in waste piles outside of the nest. That means the colored patches, the authors say, are best described as toilets.
But why didn’t ants working in the sanitation department remove the poop along with the other waste? That’s still a mystery for now. Although, the presence of toilets within the nest suggests that their excrement probably isn’t riddled with pathogens. It may even have a beneficial role: Maybe the ants are mining the poop for nutrients for larvae, or maybe they’re using it as fertilizer for their fungi.
Images: shutterstock.com (top), 2015 Czaczkes et al. (middle)