Notes on the behaviour of Ocypode ryderi Kingsley (Crustacea,Brachyura)

The main aggressive patterns of Ocypode ryderi are described: the claws can be pointed downwards in a shield‐like position against a facing opponent or out stretched against an opponent coming from behind. While the first pattern often induces an analogous reaction in the opponent and can easily be followed by a fight consisting in reciprocal claws hitting, the latter always leads to avoidance of a further attack. A waving display occurs in courtship. The main defensive patterns against predators or men consists of a zig‐zag flight towards the sea or the burrow and a “terrifying” sound emitted by striking the claws together. Running and cleaning are executed as in the majority of the Ocypode. An attempt to compare these patterns with those of other species of Ocypode has been made.