Fiddler crabs are a small type of eight-legged crab or crustacean that belongs to the genus, Uca, the order, Decapoda, and the family Ocypodidae. There are about 100 different species of fiddler crabs and approximately 20 of these are found in Australia. It’s very easy to tell the difference between a male and female fiddler crab as the male has one claw that is much larger than his other claw.
The larger claw in male fiddler crabs may be the left or the right. The male crab waves it to attract females for mating and also to challenge males to fight. Fighting between males is not usually very aggressive. Female fiddler crabs that are ready to mate are the ones that choose male crabs to mate with, walking by many claw-waving males before selecting one for mating. The egg-carrying female takes over the male fiddler crab's sand burrow home and he must often fight other males for a new home.
The batch of eggs that the female fiddler crab carries is called a sponge. The tiny baby crabs hatch into the water when they are larvae, looking nothing at all like developed crabs. There are thousands of babies in a sponge and many of them get eaten by predators after hatching. The ones that survive eat plankton. Fiddler crabs usually live for one year or one and a half years at most.
Fiddler crabs experience growth through molting, or absorbing their old shells and growing new ones. Most fiddler crabs molt at least once a year. A fiddler crab is likely to live in a group of thousands of others, with each crab having a separate sand burrow home. Fiddler crabs are said to have the ability to sense the odor of their own species.
Some species of fiddler crabs live in mud, while others can survive only in sand. A few species live in rocky areas. A fiddler crab breathes air, but must always stay near water as the gills must be wet at all times. Fiddler crabs use their small claws to gather food and since males have only one feeder claw, they take longer at this than females. The fiddler crab ingests food particles from bacteria, rotting plants and algae by using his or her mouth as a scraper.
