Tripod holes 46

huge number of Atlantic sand fiddler crabs Uca pugilator congregating along high tide influx, south end of Topsail Beach, NC
N 34°20’56.61″ W 77°39’20.41″ Google Earth location

While walking along this beach, The Girlfriend and I found it a little curious to stumble upon a long hollow filled with scattered gravel, until we realized that it wasn’t gravel at all, and then we boggled at it. Instead, these are all Atlantic sand fiddler crabs (Uca pugilator,) thousands of them, and the hollow is a swale that floods at high tide. Once the tide recedes, the crabs begin foraging for microorganisms within the recently-submerged sand, following the path all the way back to a very small pond that remains at low tide. We’ve been there multiple times now, and my guess is that this will go on until a storm reconstructs the island geology, which (knowing the Atlantic coast) could occur at any time.

The crabs will disperse upon a close approach, but it tends to be very close, so getting a good look isn’t difficult, and capturing one takes only a quick dive – they average only a couple centimeters in width and their pincers, even the big ones, aren’t too effective, nor do they seem to use them offensively against people (unlike the Atlantic blue crabs.) Following the path up to the pond/puddle will reveal a mosh pit that’s almost disturbing.

Atlantic sand fiddler crabs Uca pugilator clustered tightly on edge of tidal pool
I can easily understand how many people find this creepy, and the resemblance to spiders is more than passing, but these are completely innocuous little critters and it’s amusing to watch them sidle out of the way if you reach for them, not in a fearful way, but as if you have BO (though, given my habits when out on the beach, we cannot rule this out entirely.) Faintly visible in both images is the evidence of their foraging, little balls of sand left behind when the crabs gather some up, turn the grains over in their mouths to remove their food, and deposit the wet sand in little spheres. Meanwhile, some much larger aquatic crab (these fiddlers are primarily terrestrial) was appearing at times from the deeper recesses of the tiny pond to snag a fiddler meal from the edge – it’s practically home delivery. Yet I cannot fathom how other species weren’t out there devouring this smorgasbord of crustaceans; I’ve seen seagulls and the small waders absolutely ecstatic about some of the little ‘sand fleas’ that wash in with the waves, so I’m guessing these guys are unpalatable in some way – I admit to not trying any myself, despite the ease of getting some samples.

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