Fiddler Crab Facts: All You Need To Know

Fiddler Crab

If you’re looking for a pet crab, Fiddler Crabs might be one of the best choices you have. These little creatures are incredibly adorable and have a fun and active personality.

In recent years, Fiddler Crabs have been quite popular as household pets.

Today, we’re going to tell you everything you need to know about Fiddler Crabs and keeping them as pets. We will cover all the facts, right from the basics to the most unusual ones.

Let’s get going!

Contents show

Fiddler Crabs Classification

  • Genus – Uca
  • Subfamily – Ucinae
  • Family – Ocypodidae
  • Infraorder – Brachyura
  • Order – Decapoda
  • Class – Malacostraca
  • Subphylum – Crustacea
  • Phylum – Arthropoda

Also known as “Calling crabs” occasionally, Fiddler Crabs are small arthropods belonging to the family of crabs.

Did you know that there are over 90 different species included in the family of Fiddler Crabs? While it is virtually impossible to gather knowledge about each one of them, we can focus on those three species that are native to the United States and are commonly kept as house pets.

These are:

Sand Fiddler Crabs

  • Scientific name – Uca pugilator
  • Carapace width – 21 millimeters (0.83 inches)
  • Habitat – sandy intertidal

The Sand Fiddler Crabs inhabit the Gulf Coast along the Atlantic and can be found in the southern parts of Massachusetts, throughout Florida, as well as in the Gulf of Mexico.

These crabs have grey eyes and small yet thick body which appears to be squarish in shape. Their body is mostly white with an occasional hue of yellow.

During the breeding season, the males display in the center of their shell a bold patch ranging from pink to purple in color.

Out of their two claws, the smaller one is purely white, while the larger one yellowish-white with pale orange marks at its base.


Mud Fiddler Crabs

  • Scientific name – Uca pugnax
  • Carapace width – 13-18 millimeters (0.51-0.71 inches) in females; 15-23 millimeters (0.59-0.91 inches) in males
  • Habitat – muddy substrate

Also commonly known as the “Marsh Fiddler Crabs,” the Mud Fiddler Crabs are found along the eastern coast of the United States, and range from Massachusetts to Florida. However, the largest population of these little creatures can be seen in South Carolina.

These Fiddler Crabs prefer to reside in muddy areas and display significant sexual dimorphism, wherein the males are larger than their female counterparts. Both sexes are olive-brown in color, with the males possessing a blue patch that the females lack.

Both the females’ claws are similar in shape, while the males bear a large claw paired with a smaller one.


Red-joint Fiddler Crabs

  • Scientific name – Uca minax
  • Carapace width – 4 centimeters (1.5 inches)
  • Habitat – low salinity to freshwater

Also known by the name of “Brackish-water Fiddler Crab,” the Red-joint Fiddler Crabs have significant red markings all over their claws, which lends them their name. In the United States, they are found from Massachusetts to the Gulf of Mexico.

Out of all the three Fiddler Crabs species that are kept as pets in the United States, the Red-jointed Fiddler Crabs have the widest carapace. These crabs display sexual dimorphism, wherein the females have similar-sized claws and the males have one larger claw and the other one smaller.


32 Fiddler Crabs Facts

Why are Fiddler Crabs called “fiddler”?

The term “fiddler” is used to refer to someone who plays the violin. One of the claws of the male Fiddler Crabs is much larger than the other one, held in front of their body just a fiddler holds his violin. This is why they have been named “fiddler”.


What do Fiddler Crabs look like?

The Fiddler Crabs are small-sized crabs with a remarkably rectangular shell, which is characteristic of their species. Their abdomen is relatively narrower and is flexed under their body.

Both the sexes have two pairs of legs, with the third pair being transformed into claws. While the females have similar-sized claws, the males have one claw larger than the other.

Fiddler Crabs are known for walking sideways.


How long do Fiddler Crabs live?

Crabs, in general, are not very long-living creatures. On average, all crab species live about 3-4 years in captivity.

Fiddler Crabs are among one of the smaller crab species, and live up to 2 years in captivity when they are taken good care of. However, in the wild, they can live up to the age of 7 years.


How many pairs of legs do Fiddler Crabs have?

The Fiddler Crabs have two pairs of legs, with the third pair being modified into claws.


How can you distinguish between the sexes of Fiddler Crabs?

A majority of Fiddler Crab subspecies display strong sexual dimorphism, with the males having a larger claw and a smaller one, while both claws of the females are of the same size.

Some of the subspecies, such as the marsh fiddler crabs, also display partial sexual dichromatism.


Can Fiddler Crabs swim?

The body of the Fiddler Crabs is not fully designed for swimming. Although they can swim upwards, it is only up to the height of six inches and not more. If these crabs are left in water unattended for longer periods, they can also drown.


What is the natural habitat of Fiddler Crabs?

The natural habitat of the Fiddler Crabs is the coastal region, which is why these little creatures can be found on all continents, except Antarctica.


Can Fiddler Crabs breathe underwater?

Yes, Fiddler Crabs can breathe underwater. These crabs have both gills and a lung, a fact that enables them to breathe both underwater and land.


Why is the claw of a male Fiddler Crab considered important?

The claw of the male Fiddler Crab is believed to be an essential status symbol in the community of the Fiddler Crabs, and also supposedly plays a role in their mating rituals, being used in combat with the competitors. Their claw is quite heavy and makes up two-thirds of their body weight.


How do the Fiddler Crabs communicate with one another?

Fiddler Crabs communicate with a series of sequences and gestures. Both the sexes wave their claws in order to communicate.


What do Fiddler Crabs eat?

Just like most of the crab species, the Fiddler Crabs are also omnivores. In the wild, they feed mainly on algae. These little creatures are also scavengers by nature, and can, thus, feed on anything organic they can find on the surface of rocks and mud.

They have little reservation about what they are eating, which is why they are often referred to as “the cleaners of the oceans”. The claws of Fiddler Crabs help them scour for organic matters in the sand.


What kind of temperament do Fiddler Crabs have?

Although the Fiddler Crabs are known to be peaceful creatures, they don’t have much of a personality, unlike the active and curious Hermit Crabs.


Do the Fiddler Crabs change their color?

Yes, some species of Fiddler Crabs do change their color, although it is not most remarkable and can only be realized upon closer examination.

The change in their color is associated with thermoregulation; when they are exposed to a warmer temperature, the color of their carapace begins to lighten. Similarly, when they are in a colder temperature, they appear somewhat darker.


Are the Fiddler Crabs freshwater crabs?

No, the Fiddler Crabs are not freshwater crabs. However, they are considered to be so because they brackish or lightly salted water to survive.


Is the population of Fiddler Crabs threatened?

Although a proper survey of the Fiddler Crabs population has not been conducted yet, they seem to be fairly common in their habitats, with no apparent threat of population degradation.


Do Fiddler Crabs bite?

Yes, although the Fiddler Crabs are not accustomed biters, they can bite in stressful circumstances. However, their bite doesn’t contain any kind of poison and is, thus, not unsafe or lethal to humans.


Can Fiddler Crabs harm humans?

No, the Fiddler Crabs can’t really harm humans in any lasting manner. Moreover, these crabs of calm and peaceful temperament and cannot be excited easily to lash out or harm humans.


Can humans eat Fiddler Crabs?

Humans can eat most of the crabs, and the Fiddler Crabs are not much different. Although these crabs are edible, you won’t usually find people eating them.

Why? Because they are so small in size that there is too little meat on their body to feed on. Even the large claws of the males have an insignificant amount of meat.


Which animals can prey on Fiddler Crabs?

The Fiddler Crabs are mostly eaten by Egrets, Herons, Raccoons, Rails, Ibis, and Terns. The Giant Mudskipper as well as the Mangrove Kingfishers are also common predators of these crabs. Withing the crab family, the Blue Crabs are known to feed on Fiddler Crabs as well.


What kinds of sound do Fiddler Crabs make (if any)?

Fiddler Crabs are mostly silent crabs. If they want to produce sound, these crabs tap the ground with their walking legs, use both their claws to drum on the substrate, or strike it with their single, enlarged claw.


When do the Fiddler Crabs breed?

The Fiddler Crabs are pretty flexible when it comes to breeding and can breed anytime during the summer season. However, the ideal time is right after their molting, when the females’ shells are quite soft.


How do the Fiddler Crabs mate?

To prepare for the process of breeding, the males dig up an L-shaped burrow in the ground, which is somewhere between 14 to 16 inches long.

When they are ready to mate, these males stand above the hole of their burrow and wave their larger claw around in order to catch the attention of the prospective females.

One of the females, attracted by their claw, approach them and get inside their burrow. The males follow their partner inside after plugging the entrance of the burrow to mate.


How do the female Fiddler Crabs produce eggs?

Soon after the process of mating, the female Fiddler Crabs incubate their eggs over a span of two weeks and then release them into the ocean.

Their eggs take very little time to hatch and live on the surface of the ocean with other kinds of planktons at their larval stage.

As larvae, these creatures go through a series of molting, eventually entering the megalop stage to complete their metamorphosis and become fully-grown Fiddler Crabs.


Can Fiddler Crabs be kept as pets?

Yes, certainly. Fiddler Crabs are the second most common pets, after the Hermit Crabs.


What is the ideal tank setup for keeping Fiddler Crabs?

While setting up a tank for Fiddler Crabs, you must know that these crabs are not very demanding when it comes to space.

If your aquarium can contain 10 gallons of water, you can easily bring home four Fiddler Crabs. All you need to do is get a stable lid, preferably one made of mesh for proper air circulation. However, if you intend to add more crabs, you should 5 gallons of water for every single crab thereafter.

Fiddler Crabs are used to living in brackish waters, which have a low level of sanity. You must provide them with brackish water in their tanks as well. Moreover, it might be a good idea to keep a hydrometer handy, just to check the salinity level of the water at regular intervals.

Other parameters you need to follow are:

  • Gravity – between 1.005 to 1.08
  • pH level – between 8.0 to 8.03
  • Water hardness – 12 to 30 KH
  • Water temperature – between 75-85 degrees Fahrenheit


Do the Fiddler Crabs need a dry surface in their tank?

Yes, fiddler crabs absolutely need a dry surface in their tank. Among the crab-owners, more often ones that are new to it, it is a common misconception. Although the Fiddler Crabs need water for their survival, they can’t live underwater completely. Both land as well as water are equally necessary to provide them with a healthy habitat.

Burrowing, which is an important activity for these crabs, can only be possible when they have enough sand in their tank. Therefore, you must create a thick bed of artificial sand shore on one side of their tank.

If you don’t have sand in the tank already, we suggest you buy it from the pet store instead of getting it from a beach, for the safety of your pet.

An aragonite substrate can also work as a great alternative for sand, for it maintains the pH levels of the tank and provides your pets with trace minerals.


Can Fiddler Crabs escape from the tanks?

Yes. Among all the crab species that are kept as pets, the Fiddler Crabs are the best at escaping from captivity.

If the tank at your home is without a lid, you might consider getting a lid before you put Fiddler Crabs into it, or they will find a way to get out in no time.


Is it okay to take out the Fiddler Crabs from their tanks in order to play with them?

No, taking the Fiddler Crabs out their tanks frequently might not be a good idea. These crabs do not like being handled very much. In fact, it can cause undue stress for your little pets, in which case they might even try to pinch you.


Is adding toys in the Fiddler Crab’s tank a good idea?

Certainly, adding toys in the tank of your pet crabs will not only keep you entertained but provide them with an active lifestyle as well. Without them, all your crabs can do is eat, sleep, and walk around all day.

There are many toys available for you to add to their tanks; while some are very easy to create at homes, others are available both online and in the pet stores at affordable prices. Take your pick!


Which aquatic creatures are ideal to be the tank mates of Fiddler Crabs?

The Fiddler Crabs are highly social creatures and don’t mind the company of other aquatic animals. However, your options in choosing their tankmates are slightly limited because of the brackish water they live in.

Moreover, it would help if you also went with fast-swimming fish so that they can escape the claws of the Fiddler Crabs. You can keep some of the fish as their tank mates are the Swordtails, Guppies, Mollies, and Bumblebee Gobies.


Why are the Fiddler Crabs important for the ecosystem?

The consistent burrowing activities of the Fiddler Crabs lead to bioturbation and promote nutrient cycling in the ecosystem.


Conclusion: Fiddler Crabs Facts

Although not as exotic or colorful as the Hermit Crabs, Fiddler Crabs are still a great addition to your tank. They are easy to care for, need little interference, and can thrive in ideal conditions.

If you have been thinking of getting a couple of these crabs for your tank, today is your day!

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