What is a Fiddler Crab?

What is a Fiddler Crab?

Genus uca

The common name of Fiddler Crab comes from the males' feeding style; the small claw of the fiddler crab looks as if it's playing a fiddle on the crab's larger claw.

image source

Currently, 103 extant species of fiddler crabs have been found and it is presumed that other species exist. Fiddler crabs have been found in many areas around the world such as the coasts of the Atlantic and Pacific oceans. This link has one of the most up to date locations where fiddler crabs can be found. Fiddler crabs are typically found in marshes and feed on any organic matter available; they have been observed eating mud then filtering the mud out into tiny ball looking pellets while keeping the nutrients they get from the organic matter. They only come out at low tide to eat and find mates as they have to burrow down when high tide comes around.

It is quite a spectacle to watch males try to seduce females into coming into burrows with them. To do this, they wave their large claw at the female. Females then pick their mate based off of claw size and off of the performance of the wave itself. The performance does not always work; some male fiddlers will force females into burrows.

I love fiddler crabs as they're a keen part of coastal ecosystems, particularly marshes. They're a food source for many animals and help clean up some of the leftover organic matter.

I'm doing research on three species of fiddler crabs: Atlantic mud, Atlantic sand, and red-jointed fiddler crabs. I plan on writing up a post over each species within the next few days to a week depending on the time I have from classes and work. If you'd like to learn more feel free to follow me or ask any specific questions you have below.

Sources:

http://www.fiddlercrab.info (used as reference for locations)
Rosenberg, M.S. (2014) Contextual cross-referencing of species names for fiddler crabs (genus Uca): An experiment in cyber-taxonomy. PLoS ONE 9(7):e101704. (Aformentioned site recommends citing this if any information from the cite was used)

*the rest of this information is what I've learned in classes and independent study of the species in the field.

NOTE: Fiddler crabs are not freshwater species, do not buy them from a pet store and keep them in fresh water, they will die within a month of you doing this!