Despite their sweet name, some species of sugar ants have an affinity for human and animal urine – a taste that could play a role in reducing atmospheric greenhouse gases.
Researchers from the University of South Australia accidentally came across the revelation when study author Sophie Petit found the sand-dwelling ants as they were foraging for their next delectable meal.
“When I first noticed the ants swarming to scavenge urine, it was purely by accident. But under research conditions we found that the ants determinedly mined urea patches night after night with greater numbers of ants drawn to higher urea concentrations,” said Petit in a statement.
Camponotus terebrans is a widespread species of ant in southern Australia and occur mainly on sandy soils notoriously deficient in nitrogen, a chemical essential to animals for the production of amino acids, protein, and DNA. In order to test the insects’ preferences, researchers set out traps containing varying amounts of sugar, about 20 to 40 percent, and those consisting of urine. Urine traps held 2.5 percent, 3.5 percent, 7 percent, and 10 percent urea, a colorless compound excreted in human and kangaroo urine. Researchers counted individual ants at each trap over the course of one month, as well as logged plant growth in the area after nine and 13 months.
Not only did they find that the ants were most attracted to higher concentrations of urea in both human and kangaroo urine, but during the night the insects would “mine” nitrogen molecules from areas that had been peed on and since dried out. The ants were also observed eating other insects and meat, including two dead house mice, and collecting bird guano. (The authors note in the journal Austral Ecology that their research was limited to a particular area and it is possible that the ants were also getting nutrients from other nearby sources, though no ants were observed foraging on vegetation.)
Other urine-attracted ants have been observed in India and the Caribbean, but the researchers conclude that this is the first time any have been seen “mining” dry urine from the sand over a long period of time. Native vertebrates of southern Australia have evolved such “impressive” adaptations to minimize water and nitrogen loss, allowing them to live in extreme environments with a competitive edge in environments that have limited amounts of nitrogen.
“C. terebrans are undoubtedly looking for urea in urine because, similar to certain other ant species, a bacterium in their digestive tract allows them to process urea to get nitrogen for protein,” said Petit. “This remarkable ability to extract urea from dry sand not only shows how sugar ants can survive in arid conditions but also how they might reduce the release of ammonia from urine, which leads to the production of nitrous oxide, a highly active greenhouse gas.”
Such commensal relationships should also be factored into global calculations considering greenhouse gas levels and ecosystem-wide relationships, add the researchers. Nitrous oxide (N2O) is a greenhouse gas less abundant than carbon dioxide but up to 300 times more potent. The harvesting of N2O by wild animals may play roles in future climatic and environmental predictions.