The carapace is bright-red in coloration in adults in contrast to the juvenile’s black or greenish carapace which occasionally may be speckled with cream-colored dots and can range anywhere from 5-7 cm in width. It predominantly feeds on algae using their spoon shaped tipped pinchers. G. grapsus runs with extraordinary speed and agility along the upright sides of rocks and has the uncanny ability to hide away in crevices to escape predation by rapacious birds. G. grapsus are mainly solitary but can be seen in large congregations competing for food and mates.
Order: crabs (Brachyura)
Family: square crabs (Grapsidae)
Species: Grapsus grapsus (Sally Lightfoot crab)