Shelter competition in juvenile red swamp crayfish ( Procambarus clarkii): the influences of sex differences, relative size, and prior residence

Using a resident–intruder model, 24-h resident juvenile male and female red swamp crayfish, Procambarus clarkii, were intruded upon by same or opposite sex juvenile conspecifics that were the same size or larger than the residents. Relative size was significantly related to contest outcomes. Residents that were the same size as the intruders won a significantly higher proportion of their encounters than residents that were smaller than the intruders. Overall, neither sex nor prior residence was significantly related to contest outcome. There was clear shelter-related territorial defense in both male and female juveniles, and is very similar to that shown in adult conspecifics. The provision of shelter for juveniles in the aquaculture of P. clarkii is especially important because of the shelter competition advantage of adults. This indirectly increases juvenile vulnerability to heterospecific predation and cannibalism by conspecific adults and juveniles.