Robber Ants Spend Their Days Stealing From Other Nests

Ants allocate their duties around the nest based on the caste system. Some are workers, while larger, stronger ants are “soldiers” and better equipped for fighting. And in some species, like Ectatomma ruidum, some ants are designated as thieves, according to a new study in the journal Animal Behaviour.

E. ruidum, a species of ants found from Mexico through South America, shows distinct behavioral differences between thieving individuals and more upstanding nest members. These Robin Hoods of the nest don’t forage like normal workers, but rob other nests of their foodstuffs. Unlike regular foragers, robber ants sneak into the nest of some other group of E. ruidum ants, wait for the residents to bring back a nibble of food, then carry it off. These robber ants seem to be their own unique caste, fully dedicated to the task of stealing. 

The international team of researchers found that robber ants walked faster away from their victim’s nest than they would near their own, had fewer encounters with other ants, and were more likely to pause on the way home. When the researchers grabbed the stolen food or diverted the robber ants, they were more likely to release the food or to change directions, while traditional foragers would try to keep taking their food home. In other words, they acted pretty guilty. 

As study co-author Hope Jahren told New Scientist, “They know they are doing something wrong.”

[h/t: New Scientist]