The plastic ring moves along the surface. More than 100 ants are pulling it in a joint operation. The workers doing the pulling are replaced by others while they are still moving. The leaders directing the group are also replaced, every 10 to 20 seconds. In the end, as always, the heavy load will reach its destination.
Ants have existed for hundreds of millions of years. They are found in every part of the world except Antarctica. There are about 15,000 known species, including some 250 in Israel, but only a few dozen species are capable of pulling a load collectively.
One member of this select club is the longhorn crazy ant (Paratrechina longicornis). It is about three millimeters long and is one of the most common ant species worldwide. These ants’ ability to work together to transport heavy burdens is the focus of a new study by researchers at the Weizmann Institute of Science, in Rehovot.
“We discovered many interesting things in our research into the question of how the crazy ant deals with the challenge of joint transport,” said the lead researcher, Dr. Ofer Feinerman of Weizmann’s Department of Physics of Complex Systems, in an interview with Haaretz. “One of the study’s most important conclusions is that they know how to find the optimal balance between conformism and individualism in order to carry out complex tasks.”
Individual ants are commonly seen as stupid, conformist creatures whose power stems solely from their ability to act as a group, as if the whole were greater than the sum of its parts, Feinerman noted. “In our study, we show that’s not the case, and that there is a more complex range of interactions between the individual and the group.”
It would drive you crazy too
The research was conducted in cooperation with Prof. Nir Gov of the Department of Chemical Physics and researchers in biology, brain science, animal behavior and computer science. The methods used to study the ant colonies, both in the lab and in the field, were novel enough to merit an article of their own, which was published on July 30 in the online journal Scientific Reports. The actual findings were published on July 28 in the journal Nature Communications.
The species is called “crazy” because “when someone attacks them or steps on them, they have a panic attack and begin to run very fast in every direction, seemingly aimlessly,” Feinerman said. But he argued that this behavior reflects not lunacy, but pacifism: They are avoiding confrontation.
“If someone attacks them, they flee; if someone breaks into their home, they move house,” he said, adding, “That’s one of the reasons why they don’t dig nests in the ground. For the most part, they look for an existing place of residence.”
This, however, doesn’t prevent them building super-colonies — “entire neighborhoods of individuals connected by nests and paths, through which millions of ants maintain ties and work together without fight or quarrels. And every nest has numerous queens.”
These enormous colonies and the consequent need to obtain large quantities of protein-rich food, combined with the ants’ natural timidity to turn the ability to transport loads jointly into a necessity for survival.
It all begins with one ant
It begins with a single ant. In the course of a food-gathering trip, the ant scents a potential food source, such as an insect carcass. It goes over and examines it for a minute or two. If the food source seems worth the effort, the ant will then return to the nest, leaving a scent trail behind so that it can return with reinforcements.
Transporting something jointly is a challenge, and not just because of the weight. It requires coordinated movement in the right direction and the ability to respond to obstacles or incidents that arise on the way.
From observation, “one of the first things we discerned is that there are leaders,” Feinerman said. But these leaders aren’t ants that have a special status in ant society; “a leader is one who knows where to go at that moment.”
The leader is replaced the moment it loses its ability to lead — in other words, once it no longer knows where to go, he said. It’s not clear why this happens.
“These ants have a mechanism that sometimes contradicts their conformism,” he said. “This is self-evident when it comes to the leaders, who have knowledge that the others don’t have.”
These findings led Feinerman to doubt the romantic view that ants’ ability to work together comes from the “hive mind,” a kind of collective intelligence.
“In this system, the wisdom does not come from crowds. Rather, some individuals supply the ‘brains,’ and the role of the group is to amplify the ‘muscle’ power of savvy individuals so that they can actually move the load.”
“Leadership that confers personal benefits, like power and money for humans, causes leaders to remain in their posts even when they don’t have the appropriate knowledge,” Feinerman added. “A Knesset member, for instance, wants status and a good pension, and therefore he’s willing to bend the laws or to lie. For ants, this factor doesn’t exist. Knowledge is the decisive thing.”
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