INTRUDING MALE RED SWAMP CRAYFISH, PROCAMBARUS-CLARKII, IMMEDIATELY DOMINATE MEMBERS OF ESTABLISHED COMMUNITIES OF SMALLER, MIXED-SEX CONSPECIFICS

The effects of competing asymmetries (intruder size advantage vs. prio r residence) on dominance relationships were investigated in a laborat ory setting. Sexually mature (Form I) male red swamp crayfish, 25%-27% larger than the average member of several mixed-sex communities of 20 -25 sexually mature conspecifics, individually intruded upon these com munities on successive days. Each community was invaded once a day, wi th each of these large intruders invading every community once during the experiment. Five days after the last large intruder invasion, nove l intruder group males, approximately the same size as the average com munity member, individually invaded the same communities, all communit ies being invaded once during a single day of testing. These novel int ruders were used to differentiate the effects of intruder size from th ose effects of being put into a novel environment. During each intrusi on, the frequencies of dominance, submission, aggressive standoffs, an d nonaggressive interactions between the intruder and members of the c ommunity were recorded. The large intruders on each day immediately an d virtually completely dominated all encountered community members, an d the large intruders were significantly more dominant than the novel, smaller-sized intruders. The size advantage of the large intruders ov erwhelmed prior residence in influencing dominance outcomes, even in t hese well established communities. (C) 1995 Wiley-Liss, Inc.