Malacostracans · Decapoda · Ocypodidae

Mud Fiddler Crab

Uca pugnax

Not Evaluated

It has not yet been assessed against the IUCN criteria. See full glossary

Uca pugnax is a fiddler crab of the Mid-Atlantic and north-eastern United States. Like other fiddler crabs, they dig burrows in the mud or sand banks of salt marshes, which they use to protect themselves from predators, high tide and extreme temperatures. They feed by filtering detritus from the mud, and defend their burrows against other fiddler crabs.

Size

up to 2.5 cm

Diet

Herbivore

Feeds mainly on plants.

Social structure

Colony

Lives in large concentrations, often for breeding reasons.

Sighting difficulty

Unknown

OceanHerbivore Colonial Ocean Crustacean

12countries 5parks 13dive sites1same family

Fun facts

The male waves his giant claw in a rhythmic motion to court females and warn off rivals, a gesture that recalls a fiddler and gives the group its name.
If it loses the large claw, it regrows a new one on the opposite side, often lighter and less substantial: it serves to threaten, but it fights less well.
Its burrows aerate the marsh mud and encourage plant growth, which makes it an ecosystem engineer.
The male has one disproportionate claw, almost the size of his own body, which he waves rhythmically to attract females and warn off rivals. Hence the name fiddler crab.
The other claw is tiny and is the only one he uses to feed, so the male takes twice as long as the female to eat.
It sifts the mud with its mouthparts, keeps the organic matter and leaves pellets of cleaned sediment at the burrow entrance.
Its burrows aerate the marsh sediment, which benefits the vegetation.