Fiddler Crabs: Types, Behavior And Facts

Fiddler crabs are often known as “mini” crabs for a reason: they are small! With a little less than 2 inches (5.08 cm), these crabs are really tiny, but they are extremely well adapted to the place they occupy in their environment.

Fiddler Crabs exist mainly in small pieces of microscopic food that they extract from the sand, which they filter through the mouth. When the tide recedes, they get very busy combing through the wet sand, sliding from one place to another with their fun and sideways walk.

There are more than 90 species of these semi-aquatic crabs found throughout the world, but the ones most commonly kept as pets are the mud Fiddlers and the indigenous red-jointed Fiddlers of the east coast and the Gulf coast of the United States.

Introduction Of Fiddler Crabs

Fiddler crabs, although often sold in pet stores as freshwater creatures, are marine animals that live in brackish marshes and tidal pools along oceanic coasts. Its name derives from a peculiarity of its eating behavior.

Male fiddler crabs have a single large claw. When they feed, they use the smallest claw to put food in their mouths. Its movement through the great claw looks like an arc that is drawn on a violin. (Female fiddler crabs have two small claws).

Fiddler crabs are crustaceans of the Arthropod phylum, which also contains shrimp, crayfish, lobsters and even insects. Without access to humidity and wet soil or water, fiddler crabs will literally dry out and die.

Like all crabs, fiddler crabs have a total of 5 pairs of legs, including chelipeds or “claws”. There are three pairs of legs for walking and one pair for swimming. A hard and rigid “skin” or chitin exoskeleton covers their bodies, which are only exposed during ecdysis or molting.

Fiddler crabs also need mud, sand and other aquatic sediments as a source of food. As detritivorous, they feed on “meiofauna,” life forms so small that they literally occupy the spaces between individual soil particles.

In the wild, communities of fiddler crabs live in burrows grouped in the intertidal zone. This is the portion of a coast that is covered when the tide is in and exposed when the tide falls.

During high tide, fiddler crabs fill the entrance of their burrows with sand to serve as a “lid.” They remain underground until the water recedes again. Then they emerge at low tide to sift the sand in search of food.

Types Of Fiddler Crabs

There are 97 different types of fiddler crabs, all of which are semi-terrestrial. None reach a length of more than 2 inches (5.08 cm). Only 3 native species of the United States are commonly kept as pets. Almost all specimens for sale in pet stores have been collected in the wild since the breeding of fiddler crabs in captivity is extremely difficult.

1. Mud Fiddler Crabs

Mud Fiddlers are the most common type of fiddler crab found on the east coast. The largest population can be seen in South Carolina, but these crabs can be found from Massachusetts to Florida.

As the name implies, they prefer muddy conditions. (This variety is sometimes known as Marsh Fiddler Crab).

The most distinctive feature of this subspecies is a depression in the back in the form of the letter “H”.

Their bodies are brown, but the large claw is yellow-orange or yellow-white and the long, thin stems of the eyes can be a striking turquoise blue. In addition, the inside of the large claw is studded with a row of blows.

2. Sand Fiddler Crabs

Sand fiddler crabs have thick, square bodies that are white, sometimes with a yellowish hue. A male shown during the mating season will have a pink or purple patch in the center of his shell.

The large claw is yellowish-white and often marked by a pale orange coloration at the base, while the smaller claw is white. The eyes are gray.

The outer surface of the large claw contains numerous protrusions, but they are not arranged in rows and the inner surface is smooth.

This subspecies lives along the Atlantic and Gulf coasts, from southern Massachusetts to Florida and to the Gulf of Mexico.

3. Red-Joint Fiddler Crabs

The Red Joint Fiddler crabs extend from Massachusetts to the Atlantic coast and to the Gulf of Mexico to Texas. However, they are not typically seen in the extreme south of Florida. Obviously, its most distinctive features are the red marks on the articulations or joints of the large claw.

Other Types Of Fiddler Crabs

Other species of fiddler crabs found along the Atlantic coast and the Gulf coast of the United States include

Panacea Sand Fiddler

These crabs are found in the Gulf of Mexico from the coast of Florida to Mexico on the border of Tabasco Campeche. They live in sand plains and intertidal marshes. Its projectiles reach a maximum size of 0.7 inches (18 mm)

Spined Fiddler Crab 

This species is distributed in the Gulf of Mexico from the Alabama coast to Tabasco, Mexico. They live in marshes and intertidal banks, preferring firmer and clay/sandy or clay/muddy soil types. Its maximum size is 0.9 inches (23 mm)

Gulf Mud Fiddler

The Gulf Fiddler is the most common of all fiddler crabs found in the Alabama and Mississippi marshes, although they can be found from central west Florida to the west to Texas. They prefer marshes and mud to mud/sand floors. The maximum size for this species is 1.02 inches (26 mm)

Mudflat Fiddler

The Mudflat Fiddler enjoys a wide distribution from Alabama to Texas. They are also found in the Caribbean and on the Atlantic coast of Central and South America.

These crabs prefer moderately salty marches and mangroves where the substrate is sandy silt. Its maximum size is 0.9 inches (23 mm)

Behavior Of Fiddler Crabs

In the wild, fiddler crabs live approximately seven years, but in captivity, they rarely survive more than a year and a half.

They do not always adapt well to the artificial environment of a tank and are often characterized as “freshwater” crabs when they actually need brackish or lightly salted water to survive.

Fiddler crabs do not have as much personality as hermit crabs and are somewhat challenging as tank mates for fish species because they eat anything. If a fish reaches its claws and is not fast enough to escape, it will be consumed.

Male fiddler crabs have a large claw, which represents up to half of their body weight. They brandished the claw as if it were a weapon to threaten intruders and protect their burrows.

That is, however, approximately in regard to any altercation. The idea of ​​a fiddler crab of a “fight” is more a ritualized version of a “chicken” game. The crab that presents the best show usually “wins”, which is usually the opponent with the biggest claw.

If a fiddler crab really loses its great claw in a fight or an accident, it will grow back (on the opposite side) the next time the creature moves or throws its shell.

The large claw is also used to attract females during the mating season, where, again, the claw size equals success.

In theory, the crab with the largest claw is the most attractive to members of the opposite sex. (Males also trample their legs to make noise for potential partners to notice)

During daylight hours, fiddler crabs become darker in color but begin to lighten at dusk. The color change not only responds to the altered quality of the light, but also to the rhythm of the tides.

Funny Facts About Fiddler Crabs

  • A single colony of fiddler crabs in the wild can be made up of thousands of individuals, so many that the beach seems to be crawling alive when they feed.
  • There is no predicting whether a male fiddler crabs’ large claw will be on the right or left side, however, if he loses the claw, it will always grow back on the opposite side during the next molt.
  • Fiddler crabs change color through the day in response to the cycle of the tides. They are at their lightest pigmentation at night.
  • When the tide comes in, fiddler crabs plug up the entrances to their burrows and wait for the waters to recede. They then emerge and begin scavenging the intertidal zone for food.
  • As adults, fiddler crabs are not good swimmers. These creatures are semi-aquatic. In captivity, they must have a way to get out of the water, usually on their own little private “beach.”
  • Fiddler crabs do breathe air from the atmosphere, but their gills have to be moist to process the oxygen.
  • Escaping their enclosure and drying out away from water is the most common cause of death among pet fiddler crabs.
  • A male fiddler crab’s claw accounts for about two-thirds of his overall body weight and is considered a status symbol in crab “culture” and mating rituals.
  • Male fiddler crabs are highly skilled at playing “chicken.” They wave their big claws in menacing threat displays, generally territorial in nature, but real fights are extremely rare.
  • Female fiddler crabs have been found to use their charms — and to trade sexual favors — for the protection of neighboring males in the colony. These are the only times when a female crab mates above ground.
  •  Fiddler crabs in captivity are some of the best escape artists to ever be housed in an aquarium. If you don’t have a lid on your tank, your fiddler will find a way to get out.
  • The vast majority of fiddler crabs kept as pets are caught in the wild because it is almost impossible to breed the creatures successfully in captivity.
  • Females will mate and lay eggs, but to grow to adulthood, the young crabs must spend a portion of their lives floating on the surface of the open ocean in a planktonic state.
  • The mass of eggs a female fiddler crab carries on her abdomen is called a sponge.
  • Currently, the only threatened species of fiddler crab in the world is the Ruby Fiddler found in Singapore.
  • Fiddler crabs are found on all of the continents except Antarctica.