Burrowing Ocypodoidea crabs are an abundant component ofmany tropical and temperate coastal areas and central to the ecosystemfunctioning, for instance because they recycle nutrients, are important food formany shorebirds and alter the sediment through their burrowing behaviour. Theburrow morphology of these crabs may differ between and within species, oftencorrelated with differences in habitat preferences, crab morphology andlife-history traits. Here we studied the burrow morphology and complexityof Macrophthalmus sulcatus and Macrophthalmusdepressus, by means of casts (n = 7 and 10, respectively) andburrow excavations (n = 17 and 16, respectively) at the pristineintertidal mudflats of Barr Al Hikman in the Sultanate of Oman. We foundthat M. sulcatus construct simple burrows that were in all butone case inhabited by a single crab. By contrast, all burrows of M.depressus were complex, with multiple entrances and many(deep-reaching) branches. There was a strong relationship between M.sulcatus carapace width and burrow entrance size, indicating that thesimple burrows are adapted to and made by the occupant. There was no relationbetween M. depressus carapace width and burrow entrance size,and in six burrows more than one crab was encountered, suggesting that thecomplex burrows are not made by and adapted to a single occupant. The complexburrows were found close to the shore whereas the simple burrows were found atthe intermediate tidal zone. We speculate that the striking differences inburrow morphology may be explained by difference in habitat selection of thestudied crabs, which most importantly relates to differences in sedimentstructure and tidal height. Crab morphology and life-history traits of thestudied crabs could also account for the observed difference in burrowmorphology.