Mashomack Musings: Fiddlers in the marsh

Have you ever witnessed a crab play the fiddle?

Some Shelter Island beaches are full of mud fiddler crabs. Often found by the end of Wades Beach and other salt marshes, these small crabs are very active during the summer, giving beachgoers loads of entertainment, just not in terms of music as their name would imply.

However, they are aptly named due to the “fiddling” motion of males when they wave their large claw to attract mates.

Fiddler crabs are crustaceans that can grow to about two inches long. The males have one enlarged claw, while females have two equally sized smaller claws.

They burrow dime-sized holes, which are easily viewed during low tides.

The burrows are often flooded during high tides, but fiddler crabs are equipped with both gills and a primitive lung, which allows them to live on land or be in the water. They get the best of both worlds.

The fiddlers generally feed on small algae particles, bacteria, and decaying marsh plants. In turn, they are eaten by shore birds and small mammals.

Not just fun to watch in our marshes, the high population densities of the fiddler crabs serve important niches in our marsh environment. Since there can be 70-200 crabs per square meter, they are able to oxygenate, drain and cycle nutrients and sediment within the salt marshes, which increases the growth of marsh grasses.

This is largely completed through their burrowing. In some cases, they can even serve as an environmental indicator for contaminants and insecticides.

Next time you’re at the beach, try and take a peek at these fiddlers in action. They are more important to our ecosystems than you might think.

Sarah Lewis is the conservation steward at Mashomack.