These purple-mottled crabs live in colonies in the intertidal zone of protected beaches and salt marshes. Males have one large claw that they wave around (play the fiddle) to impress females and warn off encroaching males. This large claw, while impressive, allows the male to only be able to eat with its one small claw, while females have a much easier time with their equal sized claws. Considering who is producing thousands of eggs this seems fair (smile).
Male Atlantic Sand Fiddler.
Female Atlantic Sand Fiddler
One acre of salt marsh may contain one million fiddler crabs. Any sudden movement sends them scurrying for cover.
Here you can see the entrance to a burrow. Fiddler burrows draw oxygen into the soil, enhancing growth and encouraging deeper Spartina grass roots that stablize the marsh. The burrows may be up to two feet deep and with each high tide the Fiddlers wait nice and dry behind a plug of mud until the tide recedes. In the winter the Fiddlers remain in their burrows in a type of hibernation (although they may emerge on warm sunny days), but with the return of warm weather they resume their “March on the Marsh.”
You might think the little balls scattered around are poo, but they are actually balls of sand spit out by the Fiddlers after feeding. Fiddlers feed by scraping up mud and sand with their claws and pulling out algae, bacteria, and detritus with their mouth parts.
Fiddlers consume up to 1/3 of the marsh’s net output in the form of detritus, algae, bacteria, and other matter. The Fiddlers in turn provide sustenance for many other marsh creatures.
When you approach the stands of Spartina grass at low tide, walk quickly, but quietly, with your ears and eyes open. You will hear the rustling of the grass and the snapping of hundreds of tiny claws before you actually see the Fiddler Crab March on the Marsh.