Fiddler Crab (Uca princeps)
Order: Decapoda, Family: Ocypodidea
Fiddler crabs are small, semi-terrestrial crabs; male fiddlers have one claw that is much larger than the other, while females have equal-sized claws.
The common English name, fiddler crab, comes from the manner in which male crabs feed; male crabs move their small claw from the ground to their mouth, causing them to resemble someone sweeping a bow (the small claw) across a fiddle (the large claw).
The male's large claw measures about 1 to 2 inches long, and is often as large and heavy as the rest of the crab's body. It also often contrasts in color with the rest of the crab's body. Males use their large claw at certain times of the year to attract females.
With their tall, slender eyestalks, fiddler crabs look rather extraterrestrial.
I. DESCRIPTION:
- Fiddler crabs are small, semi-terrestrial crabs; male fiddlers have one claw that is much larger than the other, while females have equal-sized claws.
- The common English name, fiddler crab, comes from the manner in which male crabs feed; male crabs move their small claw from the ground to their mouth, causing them to resemble someone sweeping a bow (the small claw) across a fiddle (the large claw).
- The male's large claw measures about 1 to 2 inches long, and is often as large and heavy as the rest of the crab's body. It also often contrasts in color with the rest of the crab's body. Males use their large claw at certain times of the year to attract females.
- With their tall, slender eyestalks, fiddler crabs look rather extraterrestrial.
II. GEOGRAPHICAL RANGE AND HABITAT:
- Fiddler crabs live near water on the mud or sand. They dig 1/2-inch-wide burrows that go almost straight down into the mud. These burrows can reach a foot deep and may hook up with other tunnels and have more than one entrance. They provide crabs with shelter from the sun and predators, and give them a place to stay during high tide.
- The burrows are filled with mud balls during high tide and have small pockets of air inside so the crabs can breathe. All crabs have gills, which they must keep moist in order to breathe.
III. DIET:
- Fiddlers eat algae and detritus (decaying plant and animal matter). When feeding, female crabs use both their claws, while males use just their smaller claw, to scoop up sand or mud, which they pass to their mouths. The crabs scour the material for algae and detritus, and eject non-edible matter in the form of small sand balls. Fiddlers must feed almost constantly, as sand and mud contain little organic matter. Since they only use one claw, male fiddlers take twice as long to feed as females.
- Most fiddlers look for food at low tide and stay near their burrows.
IV. LIFE CYCLE/SOCIAL STRUCTURE:
- Fish, raccoons and water birds prey on fiddler crabs.
- When a female crab lays eggs, she holds them to her belly until they are ready to hatch. This mass of eggs is known as a "sponge." When the several thousand babies inside the sponge hatch into the water, they are extremely tiny and look nothing like adult fiddler crabs. Many baby fiddlers are eaten by fish, but if they survive, they will find plenty to eat among the smaller kinds of plankton in the water.
- Baby crabs molt through five different stages before becoming adults after one year.
- The average life span of a fiddler is 1 to 1 1/2 years.
V. SPECIAL NOTES/ADAPTATIONS:
- Poor swimmers, fiddler crabs rarely enter water during their adult lives.
- The male uses his large claw to make rapid, vibratory movement on the surface of the mud, which can be sensed by other crabs and serves to "sound out" the mood of rival males nearby.
- Because there is no extra space inside the fiddler's hard shell, molting is the only way the crab can grow. The fiddler molts (or reabsorbs) its shell and grows a new larger one. Adult fiddlers will molt one or two times a year.
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