The Truth About the "Snake Skeletons" Washing up on Beaches

They're actually egg casings.

Whelk Egg Casing
Photo: bddigitalimages/Getty Images

Of all the mysterious things that wash up on beaches, these long skeleton-like coils are easily among the most bizarre.

It's not uncommon to come across what are sometimes called "fisherman's soap" or a "mermaid's necklace." Though they are often assumed to be snake skeletons or even spines, according to the National Park Service, they're actually egg casings in the form of long strings of connected disks.

"These egg cases are laid by the whelk, a sea snail that eats crabs and other mollusks," Cape Hatteras National Seashore explained on Facebook Saturday. "Each small compartment of the casing can house 20-100 eggs and on average can reach three feet long!"

"Females will lay a string of eggs in deep water twice a year and the babies will hatch out of the casing anywhere from 3 to 13 months," the post continued. When it's time, the baby whelks emerge from the disk through a hole in edge.

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By the time they wash up, most of the tiny whelks have already hatched and crawled away. According to officials, the casings are most likely to wash up during the spring and fall, because that's when whelks lay eggs.

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