Carpenter ant doctors amputate legs to save friends, scientists stunned

While animals are known to care for one another, surgery was thought to be exclusive to humans. However, behavioral ecologists from the University of Würzburg have discovered that ants also perform surgical procedures on their injured nestmates.

Previous research on Megaponera analis ants revealed they use antimicrobial compounds from a special gland to treat injuries and prevent infections.

In contrast, Florida carpenter ants, lacking such a gland, rely on mechanical actions to care for their injured nestmates. These ants either clean wounds or amputate limbs, demonstrating their ability to assess injuries and determine the appropriate treatment.

“This is literally the only case in which a sophisticated and systematic amputation of an individual by another member of its species occurs in the animal kingdom,” said Erik Frank, first author and a behavioral ecologist, in a recent press release.

Ants can diagnose the problem and treat it

The study examined two types of leg injuries: cuts on the femur and similar wounds on the ankle-like tibia. Femur cuts were cleaned and then amputated by ants, while tibia wounds received only cleaning.

After that scientists took Micro-CT scans of the wound sites to analyze why ants tended to wounds differently. The scans revealed that the femur contains significant muscle tissue, involved in pumping blood (hemolymph) from the leg to the body. Injuries to the femur compromise these muscles, potentially hindering the circulation of bacteria-laden blood. In contrast, the tibia has less muscle tissue and minimal involvement in blood circulation.

“In tibia injuries, the flow of the hemolymph was less impeded, meaning bacteria could enter the body faster. While in femur injuries the speed of the blood circulation in the leg was slowed down,” Frank said.

Though a damaged tibia might run a higher risk of infection, ants cannot perform surgery fast enough as it takes at least 40 minutes to complete an amputation. So, the researchers came to understand that if they didn’t take immediate action on the tibia, the ant wouldn’t survive. The ants then spend time cleaning to the wound to inhibit infection from spreading.

“Because they are unable to cut the leg sufficiently quickly to prevent the spread of harmful bacteria, ants try to limit the probability of lethal infection by spending more time cleaning the tibia wound,” senior author and evolutionary biologist Laurent Keller said.

Regardless, survival rates significantly improved in those who received these types of treatments.

“Femur injuries, where they always amputated the leg, had a success rate around 90% or 95%. And for the tibia, where they did not amputate, it still achieved about the survival rate of 75%,” Frank said.

“The fact that the ants are able to diagnose a wound,” he continued, “see if it’s infected or sterile, and treat it accordingly over long periods of time by other individuals—the only medical system that can rival that would be the human one.”

Do ants experience pain?

The behavior appears to be innate, according to Keller. They adapt their methods based on age but don’t appear to learn them.

The team now wants to investigate how these ants carry out these precise behaviors. They’re continuing their experiments on other species also to assess how many show this kind of care.

Additionally, as surgery occurs while the patient-ant is awake, researchers want to study if these ants experience pain.

“When you look at the videos where you have the ant presenting the injured leg and letting the other one bite off completely voluntarily, and then present the newly made wound so another one can finish cleaning process—this level of innate cooperation to me is quite striking,” Frank concludes in a press release .

It turns out that ants and humans share a unique behavior in the animal kingdom: performing surgery.

The study was published in the journal Current Biology .