When Sand Dollars Move on Oregon / Washington Coast the Unexpected Can Happen

Published 02/06/25 at 4:49 a.m.
By Oregon Coast Beach Connection Staff

(Cannon Beach, Oregon) – Lying around the beach, they're either of great interest to some or others don't even notice the broken up shells. Yet sometimes these little nondescript creatures do something fantastic. (Photos and video Seaside Aquarium)

For those of you who wander the Oregon coast or Washington coast, Did you know sand dollars can move around? Did you know they can inadvertently create some beautiful sand art?

It is true the sand dollar is a mindless and spineless critter. Yes, it has no spine but only an exoskeleton. But it's also true they can scoot around on land to some degree.

If you see one that's purple – and not the glaring, beached white you normally see – don't pick it up. That means it's still alive. You may be in for a treat, however, as when sand dollars move around they create some lovely patterns, like what is seen in this shot from Seaside Aquarium.

“Pacific sand dollars use the spines located on the bottom of their body to move around the seafloor,” said Tiffany Boothe of Seaside Aquarium. “They use them in a rowing motion to move through the sand. Using them in a rowing motion to move forward they can also use them to bury into the sand which helps anchor them down when currents are strong.”

That purple, fuzzy look of a live sand dollar comes from those spines – called pedicellariae.

So how fast can sand dollars move? You'd better take some patience.

“While they can move, these guys are not speed demons, their average speed is about 1/2 inch per minute,” Boothe said.

Boothe said: to be clear, these are not cilia like many creatures have. They're spines.

These spines, according to the Coastal Interpretive Center of Ocean Shores (on the Washington coast), also serve as gills on the top side of the body.

Sand dollars use these spines to grab food as well – in an interesting, rather alien manner. The spines join together to form little cones with a triangular shape to grab plankton.

Still, it's their movement that's really the most amazing, and indeed they have a bottom and a top. The video here from Seaside Aquarium shows a sand dollar upside down.

“They do have a top and a bottom,” Boothe said. “When exposed at low tide they typically bury themselves in the sand. This helps protect them from predators and stay moist until the tide comes back in.”

Another fascinating thing about sand dollars on the north Oregon coast is that northernmost Seaside and southernmost Gearhart have a ton of unbroken sand dollars. It's known there are extra large populations of them off this part of the Oregon and Washington coast, but scientists aren't entirely sure why so many wash up in the Gearhart / Seaside area (basically the mouth of the Necanicum. Why This Area Has So Many Whole Sand Dollars

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Andre' GW Hagestedt is editor, owner and primary photographer / videographer of Oregon Coast Beach Connection, an online publication that sees over 1 million pageviews per month. He is also author of several books about the coast.

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