Longhorn crazy ants, named for their jerky and erratic movements, may seem chaotic, but they are actually very cooperative and efficient at retrieving food. A new study shows that through intelligence of the swarm, worker ants are able to anticipate obstacles and clear them from a path so other ants can more easily move bulky pieces of food, improving foraging outcomes for the whole colony.
While human brains have around 86 billion neurons, ant brains, about the size of a poppy seed, have no more than a million neurons. Through a series of experiments, researchers from Switzerland and Israel learned how “swarm intelligence” is able to collectively solve problems, including efficient foraging.
Ehud Fonio, lead author of the study and a research fellow at the Weizmann Institute of Science in Israel, said in a press release that it is the first documented case of ants showing “forward-looking behavior” as they cooperated transporting food. He said the longhorn crazy ant (Paratrechina longicornis) workers have the ability to “clear obstacles from a path before they become a problem — anticipating where a large food item will need to go and preparing the way in advance.”
The authors were inspired to study the behavior after seeing longhorn crazy ant workers move gravel pebbles out of the way for a group of workers transporting a large insect.
The researchers conducted 83 experiments at the institute’s campus, using cat food pellets, which the ants liked, as prey and plastic beads as obstacles. They found that the ants only cleared the path if it was really necessary or when the food item was big. They cleared less when the food was in crumbs and easily moved by individual ants.
Clearing the path first was a significant time saver; if the path was not first cleared, it took the ants 18 times longer to get around the obstacles.
“Humans think ahead by imagining future events in their minds; ants don’t do that,” Ofer Feinerman, a professor at the Weizmann Institute, said in the statement.
Ants first inform the swarm of the presence of food by depositing tiny droplets of pheromone on the ground as they run erratically. The other ants are prompted to clear the way by detecting the pheromones from the foragers.
“Individual workers don’t understand the situation at all. This intelligent behavior happens at the level of the colony, not the individual. Each ant follows simple cues – like fresh scent marks left by others – without needing to understand the bigger picture, yet together they create a smart, goal-directed outcome,” Danielle Mersch, a co-author of the study and former postdoctoral researcher at the Weizmann Institute, said in the press statement.
“These ants thus provide us an analogy to brains, where from the activity of the relatively simple computational units, namely neurons, some high cognition capabilities miraculously emerge,” Feinerman said.
Banner image of a longhorn crazy ant by Ajay Narendra via Wikimedia Commons (CC BY-SA 3.0).
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