The effect of population density on spacing patterns and behavioral interactions in the cockroach, Byrsotria fumigata (Guérin)

A dominance hierarchy, in which one individual was dominant over all other individuals but in which the relationships among the subordinates were unclear, was observed in male groups of the cockroach, Byrsotria fumigata (Guerin), over a wide range of population densities. There was no tendency towards territoriality, even in low density populations. The rate of interindividual interactions remained nearly constant at all densities, but the number of contests in which one animal was a clear winner decreased significantly as density decreased. Certain behavioral acts, including submission, decreased with decreasing density, while others, such as fleeing, increased. The social repertoire seems to be relatively plastic, depending upon the density at which animals are kept. Usually hierarchies were maintained when groups of animals were transferred from one density to another, but in some cases a previously subordinate animal became dominant.