Sand Bubbler Crabs at Cape Tribulation 10 – Alongside clumps of stranded dead seaweed are isolated darker patches of sand on the tide lines left by the receding water. They 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 central burrow to which the crab retreats periodically. Each line of pellets represents an individual foraging trip during which the organic content is stripped from the sand grains.
Jessica's Nature Blog 