Ants may be the only animal that performs surgical amputations

Amazing stuff! Whether surgery or other treatment is performed depends on the location of the injury!

"In his 11 years studying ant behavior, biologist Erik Frank had never seen anything like it. He and his colleagues at the University of Würzburg brought Florida carpenter ants back to their lab in Germany to learn how they respond to injury. Most ant species treat the injured or severed limb of a comrade by coating it with an antimicrobial goo. But the reddish-brown carpenter ants took a different tack: They bit the remainder of the limb off, effectively amputating it. ...

With a pair of microscissors, the researchers also injured the ants’ legs lower down, at the tibia. This time, fellow insects did not amputate the appendages of their injured nestmates; instead, they simply licked the wound to remove bacteria with their tongues. Ninety percent of the isolated ants died, whereas 75% of those that returned to the nest survived. ...
The difference in the tactics employed by bystander ants may lie in the insects’ physiology. High-resolution microscopy revealed that the Florida carpenter ant’s femur has several muscles that impede circulation of hemolymph (the insect version of blood), stopping the bacteria from quickly entering the body. As a result, the ants may be more likely to amputate femur injuries because they have the time needed to perform this procedure ...

Surprising: Amputations are Only Performed on Injured Thighs

Researchers ... made another astonishing observation: The ants only proceed to amputation if the leg injuries are on the thigh (femur) – regardless of whether the wounds are sterile or infected with bacteria.

If, on the other hand, the wounds are on the lower leg (tibia), they never amputate. Instead, the ants put more effort into caring for the wounded in such cases ..."

From the abstract:

"Open wounds pose a major infection and mortality risk in animals. To reduce these risks, many animal species apply antimicrobial compounds on their wounds. Ant societies use antimicrobial secretions from the metapleural gland to sterilize the nest and to care for injured individuals. This gland has been lost over evolutionary time in the genus Camponotus and a few other genera. Using behavioral and microbiological experiments to study how Camponotus floridanus handles infected wounds, we uncovered a new mechanism to fight infections in animals. When a worker was injured at the level of the femur, other ants amputated the injured limb by biting the base (trochanter) of the injured leg until it was cut off. However, when the injury was at the level of the tibia, other workers directed more wound care than when the injury was at the level of the femur, but they did not amputate the injured leg. Experimental amputation led to increased survival of ants with infected wounds when the injury was located at the femur but not when it was located at the tibia. Overall, this study does not only provide the first example of amputations as a means to treat infected individuals in a non-human animal, but also demonstrates that ants can adapt their type of treatment depending on the wounds’ location."

Ants may be the only animal that performs surgical amputations | Science | AAAS Surprising tactic may be way to prevent entire colony from being infected by bacteria

Amputations Save Lives – Even in Ants (original news release) In an emergency, ants bite off injured limbs of fellow ants to ensure their survival. Whether they take this radical step depends on the location of the wound.

Wound Dependent Leg Amputations to Combat Infections in an Ant Society (no public access)

Amputation when wounded: An ant bites off the leg of an injured conspecific. It then treats the wound by licking it.