Those sand balls you see along the Texas coast are made by small crustaceans

Fiddler crabs dig burrows along the beach

If you look closely at the burrow in the picture, you’ll notice that the mudballs are piled up on one side of the burrow like a fence. (National Park Service)

PADRE ISLAND NATIONAL SEASHORE, Texas – Have you ever been to the coast and wondered what those little sand balls are that appear in clumps throughout the beach?

Padre Island National Seashore officials say they’re made by fiddler crabs.

Male Fiddler Crab, Bolivar Peninsula, Texas - July 2009 (Flickr)

The mounds of sand balls are often found next to small holes, or burrows, that are roughly the size of a pinky finger.

Male and female crabs dig the burrows and scurry into them to avoid the heat of the day and they also provide shelter from predators, PINS officials said in a Facebook post.

“But scientists think that there might be more to the crab’s - particularly the male’s - ‘mudballing’ behavior than just a cleaning out his burrow. Some scientists suggest that the female fiddler might take the size of the mudballs into consideration when choosing her mate,” the Facebook post states.

The mudballs might also play a role in defining a male fiddler crab’s territory.

If you’ve ever been wandering around on the flats on the laguna side of the island during low tide, then you’ve likely...

Posted by Padre Island National Seashore on Monday, May 23, 2022

“If you look closely at the burrow in the picture, you’ll notice that the mudballs are piled up on one side of the burrow like a fence. Since fiddler crabs do most of their courting just outside of their burrow, scientists suggest that this barricade might serve as a visual deterrent to potential competitors,” PINS officials said.

So the next time you find yourself at the beach, keep an eye out for fiddler crab burrows.

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About the Author:

Mary Claire Patton has been a journalist with KSAT 12 since 2015. She has reported on several high-profile stories during her career at KSAT and specializes in trending news and things to do around Texas and San Antonio.