Have you ever wondered what the tiny balls of sand are on our beaches, well this little crab is responsible.

Sand Bubbler - Scopimera inflata - Photo by Alex Pawlow

The sand bubbler crab lives in burrows on sandy beaches, between the low and high tide mark. A couple of hours after the tide goes out, the crab emerges from the burrow to forage on detritus deposited by the high tide.

They create the balls of sand whilst filtering the sand for organic matter, and create patterns based on the order they work through the sand.

They are highly predated by many bird species, and understandably are skittish and difficult to spot. They also have excellent camouflage, being sand coloured and mottle white spots. The claws are white.

They are also relatively small, being around 12mm across the shell.

The easiest way to see them work is to sit quietly on the beach a couple of hours after the turn of the low tide.

Studies have shown there is a type of "pecking order" with these crabs. The males stake out the higher, landward side of the beach, while females and juveniles are usually burrow closer to the water. Males especially are very territorial, and tiny battles can be observed where the crab will raise itself up to display its size to an encroaching crab. Occasionally, if the pair are matched for size, they will lock claws and battle for their patch of sand.