Beebe’s Fiddler Crab, Uca beebei (Fiddler Crab of the Week)

Note: the fiddler crab of the week series was temporarily derailed due to some unexpected health issues, but will hopefully be back on track going forward.

This week we find another species from the Pacific coast of the Americas, Uca beebei, named after the famous naturalist, explorer and author William Beebe. This small species is found from El Salvador through Peru on open mudflats. In the Pacific entrance of the Panama canal it tends to be one of the more numerous species, often found mixed with larger species such as Uca stylifera or Uca heteropleura or more similarly sized species such as Uca deichmanni. Relative to many other species, it is also more of a generalist when it comes to substrate preference, ranging across both sandier and muddier mudflats. Not the most colorful species, it tends to be a grayish-brown with some teal on the back of the carapace; the long, slender fingers of the large claw are white, while the rest of the major limb often has dark purple highlights. The eyestalks are thick and yellow.

Photo provided by Pat Backwell.

Unlike many of the other species in the series so far, Uca beebei is actually fairly well studied. John Christy and colleagues spent many years studying the behavior of this species in Panama. It has a fairly classic, basic wave, quickly moving laterally its claw to the side, then forward in an overhead circle back to the rest position. The small claw often goes up and down as well. The waving can be done either standing in place or sometimes shuffling toward or away from another crab.

Beebe’s Fiddler Crab is one of a number of species which build structures around the mouth of their burrow. As seen in the photo below, the males build a sort of wall or pillar or partial hood on one side of the burrow opening. The exact purpose of these structures is unknown, but in part it seems to be used as a beacon to allow themselves to find their burrow more quickly if they’ve wandered away from it.

Photo provided by Pat Backwell.