Ant colonies behave like neural networks when making decisions – | Region & Cash

An ant colony leaves its nest after a temperature change. Photo credit: Daniel Kronauer

Temperatures are rising and an ant colony will soon have to make a collective decision. Each ant feels the rising heat under their feet, but carries on as usual until the ants suddenly reverse course. The whole group storms out as one – a decision to evacuate has been made. It’s almost as if the ant colony has a larger, collective mind.

A new study suggests that as a group, ants actually behave similar to networks of neurons in a brain.

Rockefeller’s Daniel Kronauer and postdoc Asaf Gal developed a new experimental setup to meticulously analyze decision-making in ant colonies. As reported in Proceedings of the National Academy of Sciencesthey found that when a colony is evacuated due to rising temperatures, their decision depends on both the magnitude of the heat rise and the size of the ant group.

The results suggest that ants combine sensory information with their group’s parameters to arrive at a group response – a process similar to neural computations that lead to decisions.

“We developed an approach to understand the ant colony as a cognitive-like system that perceives inputs and then translates them into behavioral outputs,” says Kronauer, head of the Laboratory for Social Evolution and Behavior. “This is one of the first steps to truly understand how insect communities engage in collective computations.”

A new paradigm

At the most basic level, decision-making boils down to a series of calculations aimed at maximizing benefits and minimizing costs. For example, a common type of decision-making called the sensory response threshold requires an animal to detect sensory input, such as heat, beyond a certain level in order to elicit a certain costly behavior, e.g. B. to move away. If the temperature rise isn’t big enough, it’s not worth it.

Kronauer and Gal wanted to study how this type of information processing occurs at the collective level, where group dynamics come into play. They developed a system that allowed them to selectively disrupt an ant colony with controlled increases in temperature. To track the behavioral responses of individual ants and the colony as a whole, they marked each insect with different colored dots and tracked their movements with a tracking camera.

As expected by the researchers, colonies of a fixed size of 36 workers and 18 larvae reliably left their nest when the temperature reached around 34 degrees Celsius. This realization makes sense intuitively, says Kronauer, because “if you get too uncomfortable, you leave.”

However, the researchers were surprised to find that the ants did not only react to the temperature itself. As they increased the size of the colony from 10 to 200 individuals, the temperature required to trigger the decision to leave increased. Colonies of 200 individuals, for example, held out until temperatures rose above 36 degrees. “It seems that the threshold is not fixed. Rather, it is an emergent property that changes with group size,” says Kronauer.

Individual ants are unaware of the size of their colony, so how can their decision depend on that? He and Gal suspect the explanation has to do with how pheromones, the invisible messengers that pass information between ants, scale their effects when more ants are present. They use a mathematical model to show that such a mechanism is indeed plausible. But they don’t know why larger colonies would need higher temperatures to pack. Kronauer ventures that it could simply be that the larger the colony, the more troublesome it is to relocate, raising the critical temperature at which resettlement occurs.

In future studies, Kronauer and Gal hope to refine their theoretical model of the decision-making process in the ant colony by intervening in additional parameters and seeing how the insects react. For example, they can manipulate the levels of pheromones in the ant enclosure or create genetically engineered ants with different abilities to detect temperature changes. “What we have been able to do so far has been to disrupt the system and accurately measure performance,” says Kronauer. “In the long term, the aim is to reverse engineer the system in order to gain ever more detailed insights into its inner workings.”

As ant colonies grow larger, new foraging behavior emerges

More information:
Asaf Gal et al, The Emergence of a Collective Sensory Response Threshold in Ant Colonies, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2123076119

Provided by Rockefeller University

Citation: Ant colonies behave like neural networks when making decisions (2022, July 20), retrieved July 24, 2022 from html

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