Pheromone communication in ants: a detailed analysis of concentration-dependent decisions in three species

Abstract

The collective behavior of ants and the emergence of self-organizing patterns in ant colonies have been explained with various theoretical approaches based on models of trail following behavior elicited by pheromones. Although existing models can explain collective behavior of ants, there is little empirical evidence on how ants precisely respond to various pheromone concentrations. Thus, important knowledge is lacking about how much realistic description of ant behavior can be provided by the models and their underlying mathematical functions. To fill in this gap, we conducted experiments with three different ant species to explore their responses to varying concentrations of pheromones that elicit ants’ trail following behavior. We found that ants’ decision making processes in trail following are best explained by psychophysical theory (PT), which describes the relationship between physical stimuli, sensory perception and decision making in humans, other primates, birds and insects. Furthermore, the theory provides clear definitions of biological parameters, such as detection- and discrimination thresholds. The species studied were distinctively different in the shape and parameters of their psychometric functions, which we attribute to specific adaptions to their environment. The observed differences are discussed in relation to their natural trail following behaviors. Our study opens a new perspective of understanding and explaining important aspects of collective ant behavior using a well-established theory of perception.