Foraging and agonistic behaviour in the ghost crabOcypode kuhliide Haan

Ghost crabs, Ocypode kuhlii, forage for food in the area adjacent to the burrow. They are relatively inefficient in finding pellets of moistened bread placed 30 cm from the burrow when tested to these for the first time. However, once crabs have discovered one piece of food, they show a marked improvement in their ability to find pieces of it on subsequent forages. Two separate mechanisms may be involved in the re‐location of a food place. One of these is associative learning; there is evidence that crabs can learn the position of food in relation to the burrow. The other is a non‐associative process. It is suggested that the discovery of food on one forage promotes a more vigilant search for further pieces of it before the start of the next forage. Two agonistic displays were observed in this study. The chela down display usually occurs in encounters in which crabs are close together and are prepared to defend some object such as food or the burrow; it is often followed by “pouncing”. The lateral merus display is usually given by the occupant of a burrow in response to the approach of another crab in the adjacent area. Agonistic interactions appear to affect the dispersion of burrows on the shore; these tended to be more evenly dispersed than expected by chance.