THE FEEDING-BEHAVIOR OF THALAMITA-CRENATA (PORTUNIDAE, DECAPODA), A CANNIBALISTIC MARINE SCAVENGER

Interactions between individuals of the mangrove swimming crab Thalami ta crenata attracted to carrion were studied in the field at one site in the Cocos (Keeling) Islands. T. crenata was found to be an omnivore and a cannibalistic scavenger. Although several crabs were usually at tracted to a carcass placed on the sandflat, only one T. crenata ever fed at a time. Larger individuals displaced smaller ones at carcasses and crabs of carapace width 2 cm wide or less were significantly under -represented among those attracted and feeding. The results are discus sed in terms of the costs and benefits of engaging in escalated contes ts with cannibalistic conspecifics. It is predicted that the duration of fights and the likelihood of escalated contests will be (a) a funct ion of the size of a bait and (b) inversely related to the nutritional status of crabs.