No Ant Left Behind

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In medieval societies, amputations were common, performed to save a life in the days before antibiotics revolutionized wound care.

Now, a new study shows that Florida carpenter ants also do such surgery, the first time this kind of behavior has been observed in the animal and insect world.

“I didn’t believe this (at first) because it was very counterintuitive,” said the lead author of a new study, Erik Frank, of the University of Würzburg, Germany.

In previous, separate research published last year, scientists found that some ants applied antimicrobial substances – produced by what’s known as metapleural glands – on the wounds of nestmates to cleanse them of pathogens.

Some ant species, including carpenter ants, however, do not have these glands, supposedly because they live in structures hewn from wood, Frank told CNN.

Nonetheless, Florida carpenter ants, a species rather common in the southern United States, are still exposed to injuries.

After one of his students serendipitously witnessed an ant biting off a wounded nestmate’s leg, Frank started investigating the behavior with his team.

They manually injured ants and infected some of the animals’ wounds. One group was kept isolated, another group had amputations performed by the scientists, and a third group was released into the colony.

The ants that returned to the nest were quickly approached by one or two comrades, which gnawed the leg above the femur, amputating it entirely, according to a review of the study in the American Association for the Advancement of Science. Ninety percent of the ants that had this “surgery” survived. In contrast, only 40 percent of those left alone lived.

Frank’s team found that most of the surviving ants were those that had injuries to the femur and had amputations performed. Meanwhile, they also observed that ants never performed amputations for lower-leg injuries because those, due to ant physiology, don’t stop infection with the same effectiveness as amputations carried out higher up the leg, something “the ants just seem to know.”

“It’s like retrieving injured soldiers from the battlefield and then treating them,” said Daniel Kronauer, an expert on ant biology at Rockefeller University who was not involved with the research.