Self-amplification as a source of interindividual variability: shelter selection in cockroaches.

Although group effect and collective decisions have been described in many insect species, the behavioral mechanisms involved in the process remain poorly documented at the individual level. We examined how individual behavior depends on the environmental context and we precisely characterized the behavioral rules leading to settlement of individual cockroaches in resting site. We focused on the spatial and temporal distribution of individuals in absence of conspecifics. Using isolated adult males of the cockroach Periplaneta americana, we showed that the quality of resting sites and the duration of the settlement exerted an influence on the individual decision-making: the probability of leaving a resting site decreased with the time spent under a shelter. A numerical model derived from experimental data suggested that this simple rule of self-amplification can also account for the interindividual variability.