HAMBURG — An ant grabs its injured companion and drags it through the savannah into the nest. Then it begins to lick its wounds. Again and again.
When biologist Erik Frank observed this fascinating behavior 10 years ago, he had no idea that his discovery would become a sensation. Nor did he know that this observation would lead to the founding of a new field of research: ant medicine. Frank witnessed how the insects heal themselves. He was the first researcher to do so.
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At the time, it didn’t look like the scientist was going to have a breakthrough in his career. He was stranded in the Ivory Coast, in a research station that had been looted in the last civil war. The young biologist, just in his mid-20s, was supposed to refurbish the station, install solar panels, set up laboratories and set up a power supply. But the containers with material got stuck at the customs office. Frank had no choice but to wait. He sat in Comoé National Park for six months with nothing to do.
And then, a stroke of luck.
The park is located in the north of the Ivory Coast, and with 11,500 square kilometers of savannah, it is one of the largest of its kind in West Africa. Today, scientists can no longer enter it because Islamist terrorists are hiding there.
In 2013, there was no electricity or cell phone reception at the research station. At night, lions roared nearby, during the day elephants passed by, snakes left curves in the sand, and Frank spent his days and weeks kneeling and crawling, looking at the ants. They became the research project of his life.
Today, he heads his own research group at the University of Würzburg. This includes a small laboratory in which Frank studies the behavior of various species of ants. Someone has stuck a sticker on the door: a do-not-enter sign for anteaters. Biologist humor.
It smells bad inside. “That’s what it smells like when you keep ant colonies,” Frank says.
Carpenter ants, leaf-cutter ants and giant ants live in glass bowls and plastic boxes. They all do something that Frank discovered during his lonely days in the savannah and that he still talks about enthusiastically in his laboratory in Würzburg: They don’t just transport injured members of their species to the nest; they perform surgeries on them and treat them with medication. Ants have been practicing medicine for much longer than humans. Frank hopes that their knowledge will one day help save human lives.
They are an army
Back in the Ivory Coast, the young biologist followed Matabele ants when they hunted termites in the vicinity of the station. With a body length of two centimeters, they are powerful ants. Their colonies, on the other hand, are quite small, numbering hardly more than 2,000 insects.
Before the ants set off on a raid, scouts look for termite feeding places and carefully scout them out before hurrying back to the nest. There, they recruit hundreds of soldiers within minutes. The ant army marches in an orderly fashion toward the termites. Shortly before reaching its destination, it gathers together. Then the ants attack.
The termite workers cannot defend themselves, but the termite soldiers will fight to the last breath. Their armored heads and powerful biting tools, called mandibles, make them dangerous even for the Matabele ants. But the attackers outnumber them. They surprise the termites, overpower the guards and kill the workers. Some ants are injured in the attack, however, as the termite guards cut off their legs or bite onto them.
It was the first documented case of a kind of triage in the animal kingdom.
It’s a war that has been going on for millions of years and that Frank has watched develop again and again. Nothing special, the biologist knew that. Until he noticed that, after the battle, ants carried away the injured members of its species. The injured rarely made it back without help. But when they were carried to the safety of the nest, they survived and learned to walk again, now with one or two fewer legs. After just one day, they were even able to swarm out again for the next raid.
The fact that social insects sacrifice themselves for their fellow insects has long been in biology textbooks. Bees do that, too. But the helper behavior that Frank observed was yet unknown. The ants only transported the slightly injured insects to the nest; they cooperated in the rescue by pulling up their legs, making them easier to carry. Fatally injured insects, on the other hand, struggled so much that their fellow insects soon gave up and left them behind. It was the first documented case of a kind of triage in the animal kingdom.
The antibiotic gland
Even more astonishing, however, was that the ants licked the wounds of their fellow ants. When Frank prevented them from doing this in the laboratory, more than 80% of the injured insects died. But if the wounds are treated, four out of five injured animals survive; the cleaning apparently prevents infections.
This behavior surprised the researcher: Up to that point, scientists assumed that the individual ants were considered of little value in the ant colony. And yet Frank proved the opposite. A sophisticated set of behaviors was put in place to care for individual animals. In other words: medicine for insects.
“I think this term is appropriate because the ants’ motivation is similar to ours: An injured animal is treated to save its life,” the biologist says. There is one subtle difference: Homo sapiens has existed for around 300,000 years. Ants, on the other hand, have existed since flowering plants existed, i.e. for around 100 million years. That’s plenty of time for evolution to test and select behaviors.
It is particularly important for social insects to ward off diseases.
From a purely evolutionary biological perspective, social insects such as ants or bees are actually more sophisticated than humans on the ladder of social complexity. At the very bottom are individual cells, and above them are organisms made up of many cells. Humans are on this level, along with cucumbers and grasshoppers. The next level are organisms made up of many cells that work together with a common goal, such as bees or ants. In biology, their states or colonies are called superorganisms.
The individual animals and their behaviour can be compared to the cells and organs in a body – the workers correspond to muscle cells, the queen ant to the ovaries or testicles, and the wound treatment would then be the superorganism’s immune system.
It is particularly important for social insects to ward off diseases. After all, these animals live together in very close quarters and are genetically closely related. This makes it easy for diseases to spread. Over millions of years of evolution, the ants have developed strategies to counteract this. And — Frank also discovered this —even medicine: Matabele ants can produce antibiotics in a gland in their bodies.
The smell is the diagnosis
And that’s where Frank’s research into the behavior of ants becomes relevant for humans. Together with colleagues, he was able to identify more than 150 chemical substances with antibiotic effects in the so-called metapleural gland of the Matabele ants.
“This cocktail is very, very effective,” says Frank — even against bacteria that have already developed a wide range of resistances to antibiotics, such as the Pseudomonas aeruginosa strain, which can cause fatal blood poisoning in humans.
Doctors often fight in vain against infections with multi-resistant Pseudomonas bacteria. It is also one of the most dangerous pathogens for ants, but the insect doctors have the bacteria well under control. They are apparently able to diagnose the infection and then treat it specifically with the right antibiotics.
They take advantage of the fact that ants communicate with each other via smell. Certain hydrogen compounds on the ant shell signal, among other things, which colony an animal belongs to or how healthy it is. If an ant becomes infected, the substances change. It is as if a person sprayed a different perfume on themselves when they were feeling weak. If other ants notice this, they use their hind legs to reach into the metapleural gland, which sits like a kind of trouser pocket at the back of the chest.
For experiments on ants, you don’t have to submit applications to the ethics committee.
The gland can produce a highly effective, individually tailored antibiotic cocktail. The ant applies this to the wound of its fellow ant. The healing successes are so spectacular that Frank believes the mixture could one day be useful for humans too. Other researchers have already tried to identify the active ingredients in order to develop medication from them.
Other animals also treat their ailments. Dogs eat grass to make themselves vomit. Cats lick their paws when they are injured. Some chimpanzees catch flies, crush them in their mouths and then press them into wounds. Orangutans use a whole range of medicinal plants to treat illnesses. For example, they swallow leaves with lots of bristles when they are plagued by worms.
These examples are anecdotal, but they show that, depending on how broadly you want to define the term, the treatment of diseases is quite common in the animal kingdom. But examining such behavior in a systematic, scientific way is difficult. You can’t cut a chimpanzee’s leg to see how it treats the wound. And yet for experiments on ants, you don’t have to submit applications to the ethics committee.
The prognosis is good
In Frank’s laboratory in Würzburg, an intern is currently handling glass bowls containing colonies of Camponotus floridanus , red-brown carpenter ants from the southeastern United States. They live in rotting wood and defend their territory against other colonies. In the process, they are injured and thrown into the dirt, which then gets into the wounds and causes infections. But they do not have a gland like the Matabele ants, in which they can produce an antibiotic secretion . That’s why the red-brown carpenter ant does something different: It performs surgeries.
And the insects clearly know exactly when such a surgery is advisable. If a carpenter ant is injured on the thigh, it is amputated — and the prognosis is good: The rest of the body remains free of bacteria and more than 90% of the insects survive.
Ants probably have the best-developed medical wound healing system in the animal kingdom.
If the wound is on the lower leg, however, amputation is less effective: the blood circulates faster and the infection can spread more quickly. In such cases, the brown carpenter ants lick the wounds more frequently, thereby reducing the risk of infection. With this treatment, 80% of the insects survive — as was the case with the Matabele ants.
If you weigh up such success rates against the risk of injury to the insects, it becomes clear that emergences make a huge difference to ant colonies. In the ant species that Frank and his team work with, between 10 and 20% of the animals are injured at some point in their lives. Diagnosis, medication, operations.
“Ants probably have the best-developed medical wound healing system in the animal kingdom,” Frank says. In view of the many abilities of the ant, he asks himself: ” What other strategies have they developed, what methods have prevailed through evolution?” He will continue to investigate this. Luckily, this time around he won’t have to spend six months alone in the savannah.
