Sand Fiddler Crab

Sand Fiddler Crab (Uca pugilator) Wikimedia image Although small in size, sand fiddler crabs can be quite territorial and defensive.  Walking along the beach you may have encountered a male sand fiddler crab with claws raised in an attempt to frighten you away from his burrow.  Males and females of this species are distinguishable by their claws.  Females have two claws of equal size, whereas males have one small claw and one very large claw. The outer shell or carapace of the sand fiddler crab is square-shaped and about 1 inch long.  Depending on the time of day and how long their burrow is covered by water, their shells can even change color.  When night arrives the shell becomes lighter in color and the animal is more visible; however, sand fiddler crabs are mostly active in the day.  During a falling tide, the crabs congregate in large numbers at the water’s edge and pick through the sand and mud looking for food.  They use their small claws to pick up sand, place it in their mouth to separate out food like bacteria, algae and plant material and then spit out the remaining sand in the form of small balls. Sand fiddler crabs prefer to inhabit in areas with sand or mud and very little vegetation.  They dig burrows in the sand and mud at or above the high tide line near salt marshes and tidal creeks.  When the tide rises, the crabs retreat to their burrows, plug the entrance with sand and emerge after the water recedes. Sand fiddler crabs have an elaborate mating process that takes place during low tide.  A male fiddler crab trying to attract a mate will stand at the entrance to his burrow and wave his large claw high in the air.  When a female fiddler crab approaches the male, his waving speeds up and he may also beat his large claw on the ground.  The pounding of the claw on the ground creates vibrations that are picked up by Barth’s organ, which is a sensory organ on the legs of both male and female crabs.  Along with digging a burrow to live in, males also dig a nuptial burrow, and if the female chooses to mate with the male they will enter the breeding burrow together.  The male plugs the entrance with sand behind them and they mate inside.  The female will stay in the burrow for up to 2 weeks incubating the eggs.  Finally, on the night of a neap tide she will emerge and travel down to the water to deposit her young in the sea. Aside from using his large claw to attract a mate, a male sand fiddler crab will also use it to threaten and battle other males.  If a male at his burrow is approached by another male he will raise his claw in the air as a threat to the invader.  Sometimes, a persistent intruder will further challenge the male for his burrow and the two will lock claws and the loser may be literally tossed aside. Although sand fiddler crabs have claws, they are not too dangerous and can be handled.  When handling a female fiddler crab, keep your hands clear of the claws.  A male fiddler crab has one very large claw and to handle him you should use one hand to keep the large claw closed, but be very careful as the claws are fragile and if handled roughly could break off.  It is sometimes best to gently pin the carapace of the crab to the ground so that you can close the claws before trying to pick it up. Set as favorite Bookmark Email This Hits: 2193 Trackback(0) TrackBack URI for this entry Comments (1) Subscribe to this comment's feed Arya said: Great info! But picking up fiddler crabs can be done gently. I place my forefinger behind him and my thumb infront... I use my thumb which is too wide to pinch to hold his claw against his own face... if he WERE to pinch he would pinch himself... Also if you can get your hand under them and lift them they will eventually sorta calm down and act tame (although not truly tamed).   report abuse vote down vote up January 06, 2008 Votes: +0 Write comment Name Email Comment smaller | bigger Subscribe via email (Registered users only) I have read and agree to the Terms of Usage. Write the displayed characters Add Comment

Last Updated ( Monday, 10 March 2008 )

 

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