Observations conducted at different places along the Moçambique coast indicate that the behaviour of Ocypode ceratophthalmus is extremely plastic, permitting a high degree of adaptation to the often vastly different shores on which they are found. When the crabs are nocturnal and when, as is usual, the burrows are intertidally placed, the greater part of the crab's life is spent beneath the sand and the periods of activity are much influenced by the tidal cycles. Apart from feeding on items of prey conveyed into the burrows and stridulating when disturbed there is no evidence that they are anything but inactive when underground. On emergence from the sand the sole major activities observed were searching for food and the digging and clearing of burrows. They are very aggressive and although cannibalism is common, conflicts between equal sized crabs are generally ritualized. Social behaviour appears limited and, except for protest stridulation and ritualized posturing during intraspecific encounters, none was observed.