Operator Doctor Ants

Living in colonies called formicaries, these tiny but important creatures cooperate for the well-being of the entire colony and are not afraid to take action in situations that affect the health of individual members.

Many ants produce antiseptic secretions to fight bacterial or fungal infections, and to treat each other’s wounds. They examine the wounds, diagnose them, determine if there is an infection and, if necessary, initiate the appropriate treatment. According to some researchers, only humans can do better than this. But the reddish-brown Florida carpenter ants (Camponotus floridanus) have lost this ability in the course of evolution. Erik Frank, a researcher at the University of Würzburg, has come to some interesting conclusions while trying to understand how these ants treat wounds.

As unlikely as it may sound, in their experiments, Frank and his team injured one of the ants’ legs in the upper thigh, exposed the wound to Pseudomonas aeruginosa, a type of soil bacterium, and then released some of the individuals back to the colony, while keeping some in the laboratory. The returning injured ants were quickly examined by the rest of the colony and the appropriate treatment was decided upon: Amputation above the thigh joint, including the injured part of the leg. The ants separated the entire leg by biting and chewing. Ninety percent of the injured ants that received this treatment survived, while the survival rate of ants that did not receive treatment in the laboratory was only forty percent.

The researchers continued the experiment, this time wounding the ants in the lower part of the leg, in the area we would call the tibia, and repeated the same process. In this case, the ants only kept the wound clean by licking it and a 75 percent survival rate was observed. Unfortunately, 90 percent of the ants kept alone in the laboratory died.

Curious about the reasons behind the different treatments depending on the location of the wound, the researchers studied the physiology of the ants using high-resolution micro-imaging methods and found that some muscles in the thigh of Florida carpenter ants inhibit blood circulation to a certain extent, slowing the entry of bacteria from the wound into the body. This gives them time to perform the amputation, which takes up to 40 minutes for injuries to the upper leg. Below the leg, in the tibia area, there are no muscles to slow blood circulation, so these wounds need to be treated more quickly and they try to stop the infection rather than waste time with amputation.

To test this physiological discovery, scientists injured the legs of some ants in the upper thigh and some in the lower shin then cut off the legs and analysed their DNA. The results supported the findings: In ants with upper leg injury, the infection stopped after amputation; while in ants with lower leg injury, the infection persisted even after amputation. Thus, amputation did not save lives in the case of a lower leg injury. The ants apparently knew this instinctively and applied different treatments for different injuries.

Frank, one of the researchers, says the footage of the experimental process is quite interesting. “After the injured ant returns to the colony, it stretches out its leg to have the wound examined and waits patiently for the amputation, which takes minutes. Then another individual arrives and starts cleaning the new wound. This level of instinctive cooperation is quite striking.” It’s also a discovery that shows that ants cannot amputate their own limbs, demonstrating the power of cooperation for colony health. Likely, other ant species that are closely related on an evolutionary level may also exhibit this behaviour.

These are, of course, only experiments to observe how ants behave in the case of leg injuries. In some cases, injured or sick individuals are completely isolated from the colony, and individuals may be sacrificed to protect the majority. In particular, in the case of fungal infections known as zombie-ant fungus (Ophiocordyceps unilateralis), which affect the behaviour of ants, sick individuals are abandoned far from the colony and frequently used paths as soon as the infection is detected.

The researchers say they will continue with their work to answer questions such as whether ants feel pain.