Ant-Nurses Treat Injured Nestmates.

Non-human animals take care of each other – surprise?

Several news outlets recently reported on a new scientific discovery: Wound-dependent leg amputations to combat infections in an ant society. While this is indeed an eye-popping announcement,  what struck a nerve with me was  one science writer’s opinion that such behavior “seems almost human”.  It implies that non-human animals are not capable of recognizing problems and finding solutions for them, of looking after and tending to each other; that humans and their brains are superior to all other beings.  It’s the old, hierarchical paradigm that permeates our culture and that science has cemented ever since Descartes’s clockwork universe: Humans are the crown of creation. It’s based on the bible’s Genesis, and many scientists never questioned this premise, even when they’re atheists. Sure, my dog can’t pack his lunch box and go to work, but neither can a toddler. This doesn’t make them less valuable. They have different sets of abilities – can you still easily put your toe in your mouth? – but this doesn’t say anything about the intrinsic value of a being. 

Florida Carpenter Ant. Image credit: Bob Peterson, Creative Commons

Okay, rant over, let’s get to the ants. The researchers reported that the injured leg of an ant was bitten off/amputated by another ant. They conducted several tests and found out that the amputation greatly reduced the risk of infection which often would result in the injured animal’s death if not amputated. The ants which had their legs severed survived 90% of the time. 

The research team found another surprising factor: ants would amputate only when the injury happened on the thigh, or femur, part of the leg. They did not amputate when the lower leg, the tibia, was injured. Further experiments came up with a possible explanation. It has to do with hemolymph, the fluid that circulates inside of ants and many other insects: there are almost ten times as many muscles in the femur as in the tibia, and the muscles help with the circulation of hemolymph. A femur injury reduces the flow of hemolymph considerably, which means that pathogens such as infection-causing bacteria won’t enter the rest of the body quickly. If the leg gets amputated fairly soon (up to one hour) after it was hurt, the injured ant had a high chance of survival. With a  tibia injury, on the other hand, the pathogens spread almost immediately and an amputation would be useless. It’s quite amazing that the ants performing the amputation are able to locate the wound and assess the necessary treatment.

Once the wounded leg has been removed, ants would keep licking the wound over a period of a few hours, making sure it stayed clean. See the video below.

While Florida carpenter ants are the only non-human animals to perform amputations that we’re aware of so far, another ant species has been known for the help and wound-care they provide to injured individuals: the Mantabele ant, a Sub-Saharan ant which feeds on termites only. Because the termites defend themselves rather fiercely,  the attacking ants often suffer injuries: a bite wound or a severed leg. These wounds easily get infected and can kill the individual. The scientist whose team discovered the amputations, Erik T. Frank from the University of Würzburg/Germany, found in 2017 that the injured Mantabele ants would use a pheromone signal to communicate to its fellow nestmates that they were hurt. Rescuers would then carry the wounded ant back home where it would receive treatment to nurse it back to health: the ants treating the patient would first clean the wound with their mouthparts, and then secrete a substance with highly antibiotic qualities which they apply to the injured limb. The researchers discovered another surprising fact: the ants performed triage. Ants which were mortally wounded – if they lost five legs, for example, they wouldn’t be able to walk any more – were left behind. But what really astonished the scientists was WHO made the decision. With humans, a doctor is in charge of triage and gives preference to patients who can be saved to those with mortal wounds. In the case of the  Mantabele ants, on the other hand, it’s the severely injured individual who refuses to be rescued! The researchers doused ants with only two legs with the pheromone that alerts the rescuers, but these ants would then flail their legs to prevent being picked up. “Seems almost human”? I don’t think so.

Matabele ant tends to the wounds of a nest-mate. Image credit: Erik Frank / University of Würzburg

I wasn’t particularly fond of ants. When I lived in my little adobe house in Coyote/New Mexico where the nearest paved road was almost ½ mile away, one could barely take a step outside without stepping on one. Also, they were sitting on the stems and under the leaves of sunflowers and other plants, and walking across the meadow would almost invariably result in being bitten several times. However, once I read about their amazing healthcare accomplishments, I realized once again how limiting the “like/dislike” judgment is. I shut out a whole world of astonishing creatures, simply because I didn’t like them. The word interest derives from Medieval Latin interesse, “to be between”, “to take part”. Any discovery, any exploration requires interest, doesn’t it. How easy it is to live in an impoverished world, simply because one doesn’t like parts of it. I had discovered this long ago when I overcame my irrational fear and dislike of spiders and snakes (I wrote about this in June of 2022). And yet, there always remain some undetected dislikes. As far as ants are concerned, I shut out some 22,000 species, some of which live in colonies of hundreds of millions of individuals! They’re superorganisms, just like bees or coral colonies, which means that they all work together for the common good of all, a quality that many humans sorely lack. They use a complex communication system which involves pheromones, touch, and also sound.  Some ants in a colony become teachers, tutoring young nest mates. They can build bridges!

Ants building a body-bridge. Image credit Igor Chuxlancev. Creative Commons

Some ants are considered pests because they may damage indoor structures or find their way into a bag of sugar. Fire ants are rather aggressive and have a particularly painful sting. Maybe one is justified to dislike these? Regardless, I have a new-found respect for ant beings and their sophisticated behavior. We certainly could learn from their selflessness anf cooperation.