One colony of ants will have to make a decision as temperatures rise. When the ants feel the rising heat beneath their feet, they carry on as usual. A decision has been made to leave the group. The ants have a collective mind.
A new experimental setup was developed by Rockefeller's Daniel Kronauer and Asaf Gal. The magnitude of the heat increase and the size of the ant group were found to be factors in the colony's decision to leave.
According to the findings, ants combine sensory information with the parameters of their group to arrive at a group response.
The laboratory of social evolution and behavior pioneered an approach to understand the ant colony as a cognitive-like system that sees inputs and then converts them into behavioral outputs. This is the first step towards understanding how insect societies engage in computation.
A new way of looking at things.
Decision-making consists of a series of computations meant to maximize benefits and reduce costs. In a common type of decision-making called sensory response thresholding, an animal has to detect heat past a certain level in order to move away. The rise in temperature will not be worth it if it isn't large.
They wanted to find out how this type of information processing happens at the collective level. They were able to control an ant colony with temperature increases. To track the behavior of individual ants and the entire colony, they marked each insect with a colored dot and followed their movements with a camera.
The researchers expected colonies of a set size of 36 workers and 18 larvae to leave their nest when the temperature reached 34 degrees Celsius. If you become too uncomfortable, you leave.
The researchers were surprised that the ants weren't just responding to temperature. The temperature needed to make a decision to leave increased when the colony was increased to 200 people. Colonies of 200 people were held out until the temperature reached 36 degrees. The threshold is not fixed. It's a property that can change depending on the group.
Individual ants don't know the size of their colony so how can they make a decision? He and Gal think that the explanation has to do with the way pheromones scale their effects when more ants are present. A mathematical model is used to show that it is plausible. They don't know why bigger colonies need higher temperatures. It could be that the larger the colony is, the more difficult it is to relocate, pushing up the critical temperature for relocations.
The theoretical model of the decision-making process in the ant colony will be improved by interfering with more parameters and seeing how the insects respond. They can change the ants' ability to detect temperature changes by altering their genetics. We have been able toperturb the system and measure the output precisely. The idea is to reverse engineer the system to better understand its inner workings.
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 Journal information: Proceedings of the National Academy of Sciences
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