Humans aren't the only species to have waste management down. Naked mole rats, honeybees, and spider mites have all developed various means of disposing of waste, with piles of poo typically forming outside their living quarters. Now researchers in Germany are reporting in the journal PLOS ONE that black garden ants studied in lab-grown colonies establish something akin to toilets inside their nests, often in the corners. The reason isn't clear, but it's possible that the insects have some sort of biological imperative not just to keep their waste from being spread about, but to keep it within their colonies instead of further afield. "Ants are indeed tidy creatures, but we must be careful not to anthropomorphize," study leader Tomer Czaczkes tells National Geographic. "They are not tidy because it brings them satisfaction, but rather because there must be a selective advantage to being so."
The researchers note that the one to four "fecal patches" that formed in each of the black garden ants' colonies did not contain other waste, such as corpses or uneaten food—those were in fact found piled outside the nests. "Why feces is not removed with other waste materials is unclear," they write. "The presence of the toilets inside the nest suggests that they may ... have a beneficial role." Czaczkes posits that the ant poop might contain nutrients needed to nurture larvae, though he adds, "If I were forced to choose, I would say that the mostly inactive ants in the nest simply do not want to leave the nest, as this would be dangerous." (Another peculiar behavior has recently been discovered in ants.)