While an ant nest may not look much like a human home, they do have at least one feature in common: toilets. A team of researchers studying ant pooping patterns have discovered that ants like to deposit their business in specific corners of the nest.
The findings, described in the journal PLOS ONE, shed light on a surprising aspect of ant sanitary behavior that has gone largely unnoticed.
"There's very little work on defecation behavior in general – not just in ants but anywhere," said lead author Tomer Czaczkes, a biologist at the University of Regensburg in Germany. That's odd, he added, given that it's "a very important part of life."
Czaczkes said he had been doing experiments on ants in little white plaster nests when he started to notice something odd: The ants were leaving little brownish patches in corners in the 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,'" Czaczkes said. "We did the experiment ... to see what really is going on."
To get to the bottom of this mystery, Czaczkes and his colleagues made 21 mini-nests for around 150 to 300 Lasius niger ants and watched them go about their business. They fed the ants sugar water – but they colored the water red or blue, to find out where the waste ended up. After two months, there were vibrant red or blue patches in select corners of each nest.
"What was surprising was they don't simply chuck it out of the nest, because that's what ants do with all their other waste," Czaczkes said.
Why not poop outside? After all, the findings show that the red and blue deposits were just poop; dead bodies, food remnants and other detritus are dumped outside the nest.
"If this feces was very dangerous stuff, they'd presumably get rid of it," he added.
It's possible that these little toilet areas serve another purpose, Czaczkes said, though it's unclear what that would be. The ants might be mining nutrients from the poop piles to feed the young larvae, which need a different array of nutrients than the adults do. Perhaps the ants are using them as fecal fertilizer, to encourage the growth of fungi (since many ant species grow and harvest fungus to eat). It could also be that the poop piles have anti-microbial properties. Some insects use feces as a defense or as a building material.
Finding out why they poop where they poop will be the work of future study, Czaczkes said. In the meantime, he wants to catch them in the act.
"First of all, I'd really like to see them defecate," he said. "It's just really hard to catch them doing it."