Fiddlers are very active during daylight hours, foraging, mating and digging burrows. At low tide they emerge from their burrows and roam over the flats in search of algae or decaying vegetation. Females have the advantage when it comes to finding and eating food, because both their claws are small and dexterous. Unlike other crabs, which use their claws or chelipeds to crush food or to grasp objects, the fiddlers' claws are used to pick up sediment, which they scrape with their mouths for food particles derived from organic matter and unicellular plants. The small claws help the females sift through the sediment, which they then redeposit on the ground in the form of pellets after removing nutrients.
Fiddlers often eat in a puddle of water to help separate the food from the sediment.
The adult male's large claw inhibits the entire feeding process, so it must generally eat twice as much or twice as fast in order to obtain the same nutrition. The three Bay species also help to maintain larger marsh ecological processes in consuming detritus from cordgrass and other plants. They contribute to the aeration of soil around marsh grasses, and thus support their growth, and stimulate the turnover of important nutrients in the soil. Fiddlers additionally play an important role in the food web by providing food for many other large predators, including blue crabs, colonial waterbirds such as egrets and herons and small mammals such as raccoons. Habitat and Life Cycle Fiddlers dig temporary burrows to protect themselves from predators during feeding, but they dig more permanent burrows for mating and sleeping, which often are tidier and more elaborate, and which they defend.