This entire group is composed of small crabs, the largest being Afruca tangeri which is slightly over two inches (5 cm) across.

In a controlled laboratory setting, fiddler crabs exhibit a constant circadian rhythm that mimics the ebb and flow of the tides: they turn dark during the day and light at night.

[5] Fiddler crabs primarily exist upon mudflats, sandy or muddy beaches as well as salt marshes within mangroves.

Fiddler crabs are found in West Africa, the Western Atlantic, the Eastern Pacific, Indo-Pacific and Algarve region of Portugal.

[6] The crab will feed through bringing a chunk of sediment to its mouth and sifting through it to extract organic material.

Once finished consuming all the organic matter from the sediment, these crabs will then deposit them as small sand balls near their burrow.

Fiddler crabs are thought to potentially act as ecosystem engineers within their habitat due to the way they rework the sediment during feeding.

[15] Whilst the crabs major claw does function as a tool for fighting and competition, it also plays a role in thermoregulation.

As the claw is so large, and these crabs live in generally hot territory, so require strategies to keep themselves cool, particularly for wandering males without burrows.

The presence of the major claw upon the male helps them keep their body temperature regulated, and decreases the chance of them losing or gaining too much heat in a given time period.

The large claw draws away excess body heat from the core of the fiddler crab and allows it to dissipate.

[16] Heat is found to dissipate significantly faster when male crabs are performing waving at the same time.

Fiddler crabs such as the Tubuca capricornis are capable of changing their colour rapidly when placed under significant stress.

This waving display consists of raising the major claw upwards and then dropping it down towards itself in what appears as a 'come here' motion, like a beckoning sign.

[27] Synchronous waving does provide a general positive benefit for male crabs attempting to attract wandering females, as a form of cooperative behaviour.

Synchrony however, does not provide an individual benefit, as females prefer to mate with the male that is leading the synchronous wave.

49 of the total species under the family Ocypodidae will construct sedimentary pillars outside of their burrows for the purposes of courtship and defense from other crabs.

In 2016, most of the subgenera of Uca were elevated to genus rank, and the fiddler crabs now occupy 11 genera making up the subfamilies Gelasiminae and Ucinae.

[37] Fiddler crabs have been known to attack small fish in captivity, as opposed to their natural feeding habits.