Beach life

The sand bubbler crabs live in burrows in the sand, and crawl out by the thousands right after the tide is out. When they emerge on to the surface of the sand they start to scour the sand for food, microscopic life called meiofauna, rolling the leftovers into sophisticated patterns of inflated pellets, which eventually cover the whole beach. The pellets are to remind them not to go through the same particles of sand twice.