Maternal territoriality as an offspring defense strategy in red swamp crayfish (Procambarus clarkii, Girard)

The offspring-defense hypothesis of maternal territoriality in solitary and semisocial mammals [Wolff JO and Peterson JA. 1998. Ethol Ecol Evol 10:227 -239] was evaluated in another taxon using maternal and nonmaternal female red swamp crayfish (Procambarus clarkii), a freshwater decapod crustacean t hat shows pronounced shelter-related maternal aggression. The maternal fema les were of three different categories: (1) ovigerous, (2) carrying primari ly stage 1 offspring, or (3) tending offspring that were primarily stage 2. Each female was in residence in an individual aquarium containing only a g ravel substrate for 24 hr prior to serial intrusions by mate conspecifics. Virtually all of the residents, maternal and nonmaternal, excavated a depre ssion (shelter) in the substrate prior to the first intrusion. The results showed that residents in each of the maternal categories won a significantl y higher proportion of their encounters than did the nonmaternal residents, which showed only negligible defense and lost every encounter. However, th ere were no significant differences in encounter outcomes between the mater nal resident categories. There was clear defense of the shelter by maternal females, with virtually all fighting being in or around it, thus demonstra ting stable, heightened territorial defense throughout these maternal phase s of reproduction. This support of the offspring-defense hypothesis of mate rnal territoriality is the first such evidence for a freshwater crustacean and is very similar to that recently reported in a related marine decapod, the American lobster (H. americanus). (C) 2001 Wiley-Liss, Inc.