Prior Residence Effects in Shelter Defense in Adult Signal Crayfish (Pacifastacus Leniusculus (Dana)): Results in Same- and Mixed-Sex Dyads

Abstract

In a variety of taxa, the initial resident in a spatial area enjoys a dominance advantage over a subsequent intruder. In decapod crustaceans this residence has been demonstrated in lobsters, prawns, and crabs. However, there is scant evidence for the effect in crayfish. In the present series of experiments, individual signal crayfish (Pacifastacus leniusculus) were introduced into one side of divided aquaria, which contained a shelter. Another crayfish was put into the opposite side. Twenty-four hours later the divider was removed. In same-sex encounters 76% of female residents retained shelter possession, as did approximately 70% of male residents, both sexes demonstrating a significant territorial prior residence effect. In mixed-sex encounters, female residents retained shelter possession against male intruders in 80% of them. However, male residents retained shelter occupancy in only 33% of the encounters with female intruders. These findings demonstrate the existence of a prior resident effect in P. leniusculus. The contest advantage of females over males is consistent with previous research showing female dominance over males in social dominance hierarchies in this species.