What are those weird spider looking creatures in the mangroves around Fort Myers Beach?

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Mangrove Crabs


On the water’s edge, along the twisted roots of South Florida’s mangrove habitat lives an otherworldly creature… the Mangrove Crab.


Looking eerily like a large spider, our local mangrove crab, species Aratus pisonii, can be found along the mangrove-lined shores of Fort Myers Beach and her surrounding areas. Full grown, these crustaceans are only approximately 2 centimeters large and are a brown and olive color, perfect for camouflaging between the knotted mangrove branches. To better climb on the wet and slippery mangrove foliage, mangrove crabs have adapted to grow small tufts of black hair so they are able to maneuver in and above the water.


Though not the cutest of creatures, mangrove crabs hold a valuable role in our local ecosystem as “engineers”. The crabs feast among the dead mangrove leaves and other organic materials on the ground, which allows for the continual growth of the mangrove ecosystem and forms a base for the food chain. As the crab break down this “leaf litter” other organisms such as detritovores and other organisms can feed on the tiny decomposing leaf bits created by the crab. The detritovores and other small organisms can be food for larger organisms that then become food for even larger organisms and so on.


Our staff knows you love the dolphins, the ospreys and all of the beautiful wildlife that lives in the Fort Myers Beach area, but it is important to also understand how important every animal is, even the small mangrove crab, to our fragile coastal ecosystem.


Whether you’re one of our eco tours, or exploring on your own, keep your eyes out for these little guys who do so much for our beloved marine and mangrove environments.


Fun Fact: Mangrove crabs and hermit crabs are the only crustaceans that can climb trees.