Sand Bubbler Crabs at Cape Tribulation 11 – Isolated darker patches of sand along the tide lines left by the outgoing sea are composed of small ball-shaped sand pellets produced by the feeding activities of the “Sand Bubbler” Crab (Scopimera inflata). Each has an erratic pattern of radiating lines around a burrow to which the crab retreats periodically to shelter from the hot sun. Each line of pellets represents an individual foraging trip during which the organic content is stripped from the sand grains.
Jessica's Nature Blog 