"While these organised structures might look like the work of an artist, they’re actually just the remnants left behind where a sand bubbler crab’s been snacking.
During low tide they exit their burrows (as seen in the top pic) to scour the sand for tiny bits of organic debris in a radial motion. While eating, the crabs ball the excess sand on their heads, then discard it when it gets too big for them to see over, leaving behind a remarkable-looking reminder which helps them keep from searching for food in the same sand twice.
Each time High Tide returns, the small structures crumble and are washed away, all while leaving behind more food particles to fuel the tiny crab’s next accidentally artistic pursuits.”
Video of the Sand bubbler crab in action:http://vimeo.com/6449515