- Scientists have discovered that Florida carpenter ants perform life-saving amputations on injured nestmates, a level of medical intervention previously only observed in humans.
- The ants assess wound locations and adjust their treatment accordingly, amputating legs injured at the thigh to prevent infection spread, while cleaning wounds on the lower leg.
- The amputations are remarkably successful, with about 90% of the amputated ants surviving the treatment and resuming their full range of duties in the nest, despite losing one of their six legs.
- This behavior is believed to have evolved as an alternative method of infection control in carpenter ants, which lack the antimicrobial-producing metapleural glands found in many other ant species.
Ants perform amputations on injured nestmates to save their lives, according to a new study. The research published in the journal Current Biology found that Florida carpenter ants (Camponotus floridanus) can assess wound locations and adjust their treatment accordingly —a level of medical intervention previously only observed in humans.
“The fact that the ants are able to diagnose a wound, 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,” said Erik Frank, a behavioral ecologist at the University of Würzburg in Germany and lead author of the study.
The research team observed that when a carpenter ant’s leg was injured at the thigh (femur), other ants would bite off the entire limb at the base. This radical procedure prevented life-threatening infections from spreading through the injured ant’s body.
Remarkably, about 90% of the amputated ants survived the treatment and resumed their full range of duties in the nest despite losing one of their six legs.
“Our study proves for the first time that animals also use prophylactic amputations in the course of wound treatment. And it shows that the ants orientate the treatment to the type of injury,” said Laurent Keller, an evolutionary biologist at the University of Lausanne in Switzerland and senior author of the study.
A Florida carpenter ant amputating the leg of a nestmate in a laboratory experiment. Video by Dany Buffat.
When a Florida carpenter ant’s leg is injured at the femur, other ants in the colony perform an amputation. They start by licking the wound clean. Then, they move up the injured leg with their mouthparts until they reach the base of the leg, called the trochanter. At this point, the ants repeatedly bite the injured leg until it’s completely cut off. This process takes about 40 minutes on average. After the amputation, the ants continue to clean the wound site.
The ants don’t seem to learn or teach this behavior, but rather just “know” what to do. “It’s really all innate behavior,” Keller said. “Ant behaviors change based on the age of an individual, but there is very little evidence of any learning.”
The ants’ medical prowess went beyond simple amputation. The researchers noted that the ants only performed amputations if the leg injuries were on the thigh. For injuries on the lower leg (tibia), the ants instead focused on intensive wound cleaning, which resulted in a 75% survival rate.
The scientist did a series of experiments to figure out why ants treat leg injuries differently depending on where they are. First, they injured the ants’ legs in different places, either on the femur or the tibia. Some injured ants were left alone, some had bacteria put on their wounds, and some had their legs cut off. The researchers watched to see which ants survived best. They also did a test where they cut off legs at different times after putting bacteria on them to see how fast infections spread. To see how well these treatments worked, the scientists measured how much bacteria was still in the ants’ bodies after 35 hours.
Lastly, they took super detailed X-ray pictures of ant legs. These scans revealed significant differences between the femur and tibia. The femur contains much more muscle mass, which is crucial for circulating hemolymph, or insect blood. In contrast, the tibia has a larger hemolymph channel, potentially allowing for faster spread of pathogens from wounds in that area. These anatomical differences help explain why ants use different treatment strategies based on the location of the injury.
This research builds on a 2023 study by the same team, which found that Matabele ants (Megaponera analis) use antimicrobial secretions to treat wounds. The discovery of this sophisticated medical behavior in ants raises further questions about the evolution of wound care in the animal kingdom.
“We will keep studying wound care behavior in other ant species and try to understand its evolutionary origins,” Frank said. “How did the ancestral wound care behavior look like? Why do some amputate while others use antimicrobials?”
Ants, including carpenter ants, play very important roles in nature. They help improve soil by digging tunnels, eat other insects, and are food for many animals. In forests, carpenter ants help break down dead wood, which recycles nutrients. Their complex social behaviors, like these newly discovered medical treatments, give us more clues as to how they’ve evolved into one of Earth’s most successful and ecologically important insect groups.
Banner image of a Florida carpenter ant performs an amputation on another ant’s leg in an experimental setting. Photo by Bart Zijlstr
Liz Kimbrough is a staff writer for Mongabay and holds a Ph.D. in ecology and evolutionary biology from Tulane University, where she studied the microbiomes of trees. View more of her reporting here.
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Citations:
Frank, E. T., Buffat, D., Liberti, J., Aibekova, L., Economo, E. P., & Keller, L. (2024). Wound-dependent leg amputations to combat infections in an ant society. Current Biology, 34(14), 3273-3278. doi:10.1016/j.cub.2024.06.021
Frank, E. T., Kesner, L., Liberti, J., Helleu, Q., LeBoeuf, A. C., Dascalu, A., … Keller, L. (2023). Targeted treatment of injured nestmates with antimicrobial compounds in an ant society. Nature Communications, 14(1), 8446. doi:10.1038/s41467-023-43885-w
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