Learn the hole truth
What creature turns rocks on the shore into Swiss Cheese?
THERE are hundreds of different pebbles on our local beach, but last week I picked up an unusual rock covered in small holes. A little investigation led me into the weird and wonderful world of the piddock.
This amazing sea creature is an expert at boring – I don’t mean it’s dreary, I mean it’s excellent at burrowing.
Tim Ferrero, marine biologist with The Wildlife Trusts, explains: “Piddocks are rather special creatures.
“They have amazing shells with very sharp teeth at one end. When they’re little they land and attach to a rock and start grinding away to make a burrow.”
Piddocks bore into softer rocks such as chalk, softer sandstone, peat and clay deposits, and pieces of wood.
Tim says once piddocks start burrowing they are pretty much fixed in place, so if you are out by the seashore at low water you might be able to see some.
“If you see soft rock such as chalk with large holes in, most will be empty but if you look closely enough you will see one or two that have actually got piddocks in,” says Tim.
At night these clever little molluscs glow. “If you are extremely lucky you may see them bioluminesce a bluegreen colour,” says Tim.
Piddocks are filter feeders, sieving small animals, plankton and pieces of organic material out of the water.
Their burrows are excellent protection from predators but even that didn’t stop one species from trying.
“Humans used to eat them,” says Tim. “They were regarded as a delicacy .”
Sometimes you can spot empty piddock shells on the beach. They are white and look like angel wings.
“The shells are actually very thin and brittle, so it’s amazing that they manage to bore into rock,” says Tim. “But once they are washing around the shore they don’t last for too long.” Luckily, we can still see evidence of these clever creatures. “I’ve got a collection of pieces of chalk that have been smoothed off into lozenge shapes,” says Tim. “Some of them have got piddock holes in, they end up looking like Henry Moore sculptures.
“They’re rather beautiful.”