Audience and information transfer in ant societies

Claire Detrain (March 17, 2011)

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The ant society is a dynamic network of interacting nestmates of which individual decision rules lead to adaptive and functional patterns at the collective level. The non-linearity of relationships between workers makes those societies displaying properties characterizing other complex systems such as a high sensitivity to the number and/or rates of interactions between system agents. In the case of ant foraging, exploitation patterns strongly depend on colony size in a non-linear and discontinuous way: the density of nestmates' interactions influences the occurrence as well as the transition from one system state to another. However, ants do not passively undergo such a density-dependent structuring effect but instead, can play an active role in tuning feed-backs loops as a function of the density of workers. We shall review the ways workers can "assess" nestmates' density through either direct or indirect cues and then can tune amplification processes such as the laying of trail recruitment according to the social context of food exploitation. Another feature of ant societies as complex dynamic systems is the occurrence of hysteresis in which prior states of ant densities influence the ways through which the whole system can evolve. We shall see how ant individuals could keep track of such prior states and accordingly tune their behaviour and communication to improve their foraging efficiency. Finally, we shall discuss how the number of foragers can also deeply influence collective choices of ant societies between resources of different values and may act in conjunction with the availabilities of food resources of poor quality upon the discriminative abilities of insect societies