Carpenter Ants Can Selectively Perform Life-Saving Amputations on Injured Nestmates

Humans now have the privilege of witnessing a lifesaving leg amputation on the injured, with no medical intervention, but in – ANTS by their fellow mates. A paper published on July 2, 2024  in the Journal “Current Biology”, explains the process of treatment and post-measures followed by ants on their injured nest mates.

Scientists have conducted an in-vivo study on Camponotus floridanus- also known as Florida carpenter ants to assess the survival rate in femur and tibia-injured ants individually. Other variants of ants, like Megaponera analis have a natural mechanism of treating wounds, which involves ants applying various proteins and antimicrobial compounds to the infected site released from the metapleural gland. But, through evolution- the Camponotus floridanus ants lack this gland. Scientists believed that amputation might be a way to prevent the spreading of infection in the injured ant. To test this hypothesis, they experimentally injured the ants in the femur and tibia regions of their legs.

It is observed that treatment protocol (amputation and wound care) given by the nest mates varied depending on the site of injury. In both cases, it is understandable that ants addressed the primary concern of preventing the spread of the infection

Femur-injured individuals were treated by initial wound care (licking and cleaning) followed by amputation of the leg completely (biting off by another ant). This treatment behaviour is seen in ants because the muscle mass gets compromised at the femur after injury, slowing down the circulation of infection-prone blood and thus giving the ants enough time to amputate the leg completely.

On the contrary, the tibia is the faster route to spread infection in the body, as there is no muscle compromising, receiving only wound care and not amputation. Through the study, scientists figured it could be because of the time constraint, as the ants required at least 40 minutes to amputate the leg. In tibia-injured ants, if the amputation does not take place immediately, the odds of survival are low. Thus, considering the possible probability of saving a fellow mate, ants spend more time cleaning the wound rather than doing an amputation for tibia injuries.

The experiment concluded with statistical results showing successful survival rates of 90 % – 95% in amputated femur-injured ants and a 75% survival rate in wound-treated tibia-injured ants. The research was conducted under sterile conditions, with different experimental models using color tags to mark the injured individuals, filmed with an infrared camera, and studied under micro CT scan. These ants were exposed to external bacterial infection to assess the mortality rate. On a comparison point, a set of injured ants was also placed in isolation in a sterile environment, which resulted in a lower survival rate than that of ants that got treated by nest mates in the colony.

Looking at nature’s creation in its finest forms, it is remarkable how the smallest ants have the capability to perform a lifesaving act closest to that of human behavior and the undeniable strength of the ant to undergo an amputation in a conscious state. “It’s really all innate behavior. Ant behaviors change based on the age of an individual, but there is very little evidence of any learning,” says Keller, Co-author of the journal.

“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,” says Frank – the first author of the journal.

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