DES MOINES BEACH PARK — As the tide slinks down the beach, a slow-motion drama is revealed: moon snail vs. butter clam, a primal contest Puget Sound’s largest snail is well-equipped to win.
With its radula, a rasp of seven rows of teeth, the moon snail countersinks its unmistakable signature: a perfect round hole, right at the clam’s hinge, to pop open its meal. As it drills, the moon snail alternately applies its accessory boring organ — such a drab scientific name, for an instrument of pure mayhem: an extendible proboscis to dab acid on the clam’s shell, easing the drilling.
Pity the clam: a moon-snail dinner is its slow but certain demise. The typical moon snail-on-bivalve takedown lasts about four days.
As the tide drops, these and other secret lives of the low tide beach are revealed. This weekend is optimal for low tide explorations, with the lowest tides of the month bottoming out at around minus 3 on Saturday at 11:22 a.m. and 12:08 p.m. on Sunday.
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The moon snail is most often seen in remnants: Its shells the size of a palm, with a spiral to one side, are a pleasing study of perfect geometry. Its egg cases are a common sight on Puget Sound beaches. The large, round, gray collars, so shiny and smooth they look like plastic, are actually a sandwich of two layers of mucus mixed with sand, with the moon snail’s eggs in the middle.
But as the tide drops low, living moon snails can sometimes be spied, their perfect domes just visible in the surface of the sand. They live most of their lives buried in the sand, their mantle extruded entirely over their shell to provide a smooth, slithery surface, so they can cruise through the grit, on the hunt for clams.
Revealed, moon snails are a bit of a shock. “I’m scared!” said Evey McIntyre, of Olympia, age 5, squirming away from an invitation by her grandparents, Gail and Sandy Sandoval, of Des Moines, to touch the oozing mass of the snail’s mantle.
Slick with mucus, thick and muscular, the snail moved with the inevitability of doom, revealing it had been interrupted in its investigation of a clam.
So large is its mantle, it is a bit much to imagine a moon snail even fits in its shell. But when alarmed, the moon snail can squeeze its foot out like a sponge and cram itself back inside, securely tucked in, beyond the reach of predators.
Abundant from Vancouver Island to Baja, moon snails live as long as 15 years, eating a clam every four or so days. Butter clams are favorites, and they can smell them as they prowl the sand.
But Evey was not beguiled. “I don’t want to touch it,” she said of the lumbering snail, taking up her yellow sand pail and shovel instead. As she undertook a vigorous excavation, beach naturalists on hand from the Seattle Aquarium gently instructed her to put back her bucket of shells — the homes of many living things.
At a tide pool down the beach, Dana Dyer, a high-school biology teacher on her summer job as a beach captain for the aquarium, lifted a surprise from the clear, cool water.
Deep purple-brown and furry with tiny cilia, top and bottom, sand dollars are not, it turns out, the smooth white discs of gift shops. Alive and at home in the wild, their edges just show in the surface of the clean gray sand, where they wedge themselves on their side. That’s so the sand dollar can present its flat bottom to the direction of the current, to capture the detritus that is their dinner, sweeping it to the tiny teeth at their round mouth.
Everywhere, there was something to explore or watch, as the low tide ebbed. Crows muttered and strutted, then happened with joy on an unattended picnic, working together to rip open a bag of barbecued potato chips. A vivid orange prize was soon stuck in each bird’s victorious bill.
The cobble of the beach was soft with green sea lettuce, and strewn with tumbled bronze tangles of kelp, relinquished by the drop of the tide. The tangy scent of seaweed and saltwater was thick in air, with not a breeze stirring. Cool morning mist clung low on the water.
As the summer sun burned it off, Mount Rainier’s dome slowly emerged, smooth white and cool as a giant ice- cream dream.
The mountain seemed to float at the horizon line, vast and serene, while in the tide pool, tiny crabs tucked up their claws, scuttling across the sandy bottom, and sculpin scooted in and out of the cover of drifting sea weed.
“It’s the best thing ever,” Dyer said, “to get to go tide pooling, be excited about what’s here, and share it.”
Lynda V. Mapes: 206-464-2736 or firstname.lastname@example.org