The ecology of ghost crabs

Abstract

Ghost crabs are the largest invertebrates on ocean shores. They are globally abundant on many sandy beaches from the tropics to temperate latitudes. A defining ecological trait of the group is its fossorial habit: The crabs excavate deep, voluminous, and complex burrows, alternating between activity on the beach surface (e.g., foraging, mating, and dispersion) and underground microhabitats. Although not true land crabs, they have evolved a range of physiological, morphological, and behavioural adaptations to semi-terrestrial habitats and hence occupy a broad spatial gradient from coastal dunes to the swash zone. Ghost crabs are the fastest crustaceans on land and have acute senses of sight, smell, and hearing. Functionally, ghost crabs are pivotal in littoral food webs as mesopredators: They are often the apex invertebrate consumers on beaches while being predated by a diversity of reptiles, birds, and mammals that forage at the land-sea interface. As consumers, ghost crabs display extraordinary trophic plasticity, occupying several trophic levels, obtaining food through a variety of strategies, and consuming a wide diversity of prey. Their diet is broadincluding predation on the eggs and young of sea turtles and shorebirds-and frequently encompasses efficient scavenging of animal carcasses.