Claws, Burrows And Salt Marsh Drama: A Fun Look At Fiddler Crabs

Feisty scuttlers everywhere! 

Those fiddler crabs seem to be pretty busy, and you get the idea that they aren't thrilled when you interrupt them. Could they team up and untie your shoelaces? Probably not, but let's take a closer look at these crusty crustaceans, so we're prepared the next time we walk along a salt marsh.

You can find these pugnacious scramblers at two Harwich Conservation Trust (HCT) properties: Coy's Brook Woodlands (at the edge of the marsh) and the A. Janet DeFulvio Wildlife Sanctuary. It's always a hoot to watch them do their sideways shuffle.

Another hotbed of fiddler crab action is at Mass Audubon's Wellfleet Bay Wildlife Sanctuary. Eliot Swift, office manager at the sanctuary, said midsummer is the peak season for observing the crabs, particularly at the end of their Goose Pond Trail, which borders Cape Cod Bay. During that time, thousands of fiddlers can be seen. 

"The ground is pretty much covered with them," said Swift.

When giant humans surprise the diminutive crabs, they launch into a reverse and disperse spectacle that the National Park Service describes this way: "The very ground seems to break apart and scatter in different directions, accompanied by a faint ‘clicking’ noise as you approach. If you walk carefully and look down you will see that the individual components making up the motion at your feet are actually hundreds, if not thousands (sometimes tens of thousands), of scurrying fiddler crabs."

What were they up to before your bothersome intrusion? Well, there's a lot to do when you're a fiddler, and it all starts with crabby romance. Male fiddler crabs have one oversized claw, which (sort of) resembles a fiddle, giving the species its name — and it comes in handy when it's time to produce the next generation.

According to the South Carolina Department of Natural Resources, "male fiddler crabs wave their oversized claw up and down to attract the attention of females for mating and to intimidate potential male competitors. They also stomp their walking legs and make noises with them in an effort to attract mates."

If the dance routine works, a female crab will enter the male crab burrow for mating, and hang around for a two-week incubation period. Then she releases the fertilized eggs, which are swept out to sea. A female fiddler can release thousands of eggs, which is helpful for continuing the species, as the larvae are highly vulnerable to predation.

Adult fiddler crabs are also vulnerable to predation by birds, fish, blue crabs and small mammals, like raccoons. There's a lot of trouble to avoid during their one- to two-year lifespan, which includes a winter hibernation period spent holed up in a burrow.

While we tend to see fiddler crabs as terrestrial animals, they have gills and a basic lung, which allows them to breathe on land. These modified gills mean "they don't need to be submerged in water all the time to breathe; they just need to get wet every once in a while," according to the Tybee Island Marine Science Center.

If you're a picky eater, you might be rather put off by the gustatory approach of these crabs. "The fiddlers take in a mouthful of mud and are able to separate out their food (algae and decaying plant and animal matter) and then spit out everything else that is inedible in one compact little mud ball," reports the National Park Service. Please don't try this at your next formal dinner party!

A fair amount of poetry has been written about fiddler crabs, and some of it is pretty inspiring. But due to copyright restrictions, we can't share them here, so we decided to compose a limerick:

We're sure you can come up with something better than this. So, grab a pen and paper, head out to the salt marsh and cook up a fiddler crab poem. You could also try sketching those little beasties, but they move pretty fast!