Fiddlers Make a Healthy Sound

Now that spring is here, life has returned to our salt marshes. Stand along the edge of a salt marsh and it may seem that the whole muddy shoreline is moving.

The muck seems to be alive, as the blackness quivers, tinged with little waving yellow flecks. Get too close, though, and it suddenly stops.

You don’t need your eyes (or head) examined. You’ve merely come upon a skittish cast of fiddler crabs.

The Atlantic marsh fiddler crab (Uca pugnax) likes nothing better than a big soggy tract of tidal mud. The crabs dig burrows, which they use for resting, mating, safety and hibernating. They eat the mud too – well, they eat the tiny bits of fungus, algae, microbes and other organisms in the mud. What they don’t digest is deposited back as little mud balls.

Because all their digging helps to aerate the marsh, fiddler crabs are great for the health of Long Island Sound’s salt marshes. And they are a nutritious meal for herons, egrets, raccoons, blue crabs and other marsh predators. (Fishermen also use them as bait, especially when they’re fishing for tautogs, redfish and sheepshead.)

Fiddler crabs generally aren’t much more than an inch or so across, with two long slender eyestalks.

Fiddler crabs, of course, are easily identified by the adult males, which grow one ridiculously large claw – an adaptation that developed to help them attract females. A bigger claw gets the girl. The large claw, called the chela, can be either the male’s left or right.

And why are they called fiddler crabs? When a male feeds, the back-and-forth movement of its small claw (from the ground to its mouth) near its large claw resembles the motion of someone moving a bow across a fiddle.

If you don’t want to go marsh-muckin’ in search of fiddler crabs, you can find them in The Maritime Aquarium’s Salt Marsh gallery.