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How do ant alarm chemicals cause different responses at low and high concentrations?
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Avoidance behaviour
Cat fleeing by upward climbing.
In the context of avoidance behaviour, the response of ants to alarm chemicals is highly dependent on the concentration of the substance, which often correlates with the distance from the source.12
- Low Concentrations: At lower concentrations, many alarm pheromones (such as certain terpenes) act as attractants, drawing other ants toward the source of the signal.2
- High Concentrations: When ants encounter these chemicals at high concentrations—typically found in close proximity to the source—the response shifts significantly. Instead of attraction, the high concentration triggers intense defensive behaviors, including rapid locomotion, the adoption of defense postures, and, in some instances, fleeing.2
This dual-response mechanism allows colonies to coordinate complex social reactions to threats. For example, in leafcutter ants, the use of multiple components with varying volatilities ensures that different behaviors are stimulated at different distances: highly volatile components alert workers from a distance, while less volatile, more concentrated components initiate aggressive behaviors like biting near the source of the danger.1