They use the claw to defend their burrows and to attract mates. Males have a highly ritualized combat of arm-waving, bobbing of the body, and standing with an open, upright stance. However compat rarely gets physical as there is too much risk of injury to both crabs. These little crabs play important roles in many marsh processes. They are important to the food web, eaten by many larger predators, such as the blue crab, rails, egrets, herons and raccoons.
Fiddler crabs are also avid burrowers.
Their activity can erode or undermine marshbanks, and burrowing and feeding affect the aeration, and hence the growth of marsh grasses. And, they stimulate the turnover and mineralization of important nutrients. At the Goodwin Islands a 2.5-acre marsh ghas more that 500,000 adult fiddlers. Their population densities are an example of the high productivity of our vital wetlands and, coupled with the crab's role in marsh processes, gives good reason to conserve ecologically important species that are so critical to our own food web.