It's not quite the Norman conquest, but another invasion is worrying locals in West Wales. Scores of octopuses have "walked" out of the Irish Sea and beached themselves on the sand in New Quay, Ceredigion, Wales Online reports.

The phenomenon has marine experts scratching their heads. "We don't quite know what's causing it," says Brett Jones, owner of a local dolphin-watching tour company. "They were walking on the tips of their legs," he adds.

More than 20 of the apparently confused creatures were reported on the sand on Friday night, and the Telegraph notes the migration continued the following two nights.

James Wright of the National Marine Aquarium in Plymouth says it is "quite odd" to see so many of the curled octopus, also called the horned octopus, on the same beach.

Wright says there were a few other octopus sightings last week in areas hit by storms. Hurricane Ophelia, then Brian, battered the Irish and Welsh coasts earlier this month.

The cephalopods, which the Guardian notes grow to about 20 inches, may be injured or sensitive "to a change in atmospheric pressure," Wright tells the Telegraph.

A marine biologist says "it’s hard to imagine" the wandering octopuses found a new food source on shore. He speculates the solitary species may be looking to reproduce.

Dry land isn't hospitable to the creatures, who hide in rocks some 10 feet below the surface. Since a number of the octopuses were dead, Jones hints they became stranded.

He's urging people to put any octopuses they come across in the future back in the sea. (Squid and chips, anyone?)

This article originally appeared on Newser: Mysterious Octopus Invasion Rocks Beach in Wales