Saturday, June 23, 2012

Ode to the Fiddler

 [Male Mud Fiddler Crab (Uca pugnax) - one claw for being sexy and doing battle, one claw for eating. All photos and text are from the marsh north of the Stone Harbor Causeway, NJ.]

Ecologists think a lot about how energy moves through ecosystems, and when it comes to salt marsh, Fiddler Crabs are key players. Sun shines, marsh grass grows, dies, decays to detritus - and then the fiddlers start eating. Watch them sometime, the male's small claw is constantly moving from mud to mouth (the female has two feeding claws, lucky her). From detritus to crab to a host of creatures - night-herons, Clapper Rails, Whimbrel, ibis, gulls.

[Female Fiddler Crabs aren't burdened with the big, handsome claw, and so can eat with both "hands."]

On the incoming tide this morning, we became completely absorbed watching Fiddler Crabs from our kayaks. We - being me, daughter Becky, and fiance Beth - found a quiet side channel and watched for almost an hour as the tide rose, gradually forcing the Fiddlers into their burrows. Fiddler Crabs have gills, but don't fare well completely submersed. As the tide rises, they retreat into their burrows and plug the hole behind them, relying on a pocket of air to sustain them until the tide subsides and they can emerge to feed again.

I couldn't resist reaching down from the kayak to poke a finger into the Fiddler Crab burrows - figuring I've been bit before, what's one more bite from an annoyed invertebrate. But the reaching finger never touched a crab, they are much deeper than a finger's reach, which explains the bills of ibis and Whimbrel, and the stealth of night-herons.

Truly, I can't recall a more enjoyable hour watching nature work her wonders.
[Two male Fiddler Crabs do battle over, apparently, a choice burrow location. We didn't detect a female to fight over.]

[Over ONE MILLION Fiddler Crabs can occupy a single acre of salt marsh. Their work consuming detritus and converting it into crab is critical to the salt marsh food chain.]


  1. Nice nonbird post. I was just admiring some Fiddlers myself this morning...I love the contrast between the tiny feeding claw and the massive fighting/waving claw on the males.

  2. Great post, Don! I especially love your description of the male fiddler crab's large fiddle claw! I may have to 'borrow' it when teaching my kids about these way important crabs!

    Mary Lenahan

    1. Thanks, Mary! Looking forward to weaving fiddlers into our lessons at the refuge. If you want full-sized versions of the images to show your students, please let me know.