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Despite many reports of animals using visual landmarks for homing, surprisingly little is known about construction of landmarks for the purpose of orientation. Semiterrestrial crabs normally use a path integration method for short-range homing, but active courtship or territorial behavior may introduce errors increasing predation risk. We explored the hypothesis that male fiddler crab Uca lactea may build structures for landmark orientation to compensate for errors during courtship. Males without burrows found an artificial burrow with a semidome from a greater distance than one without a semidome. In addition, courting males retreated to the translocated semidome rather than to the original burrow location more frequently than noncourting males did. Finally, the maximum traveling distance from the burrow and the maximum deviation of the longitudinal body axis from the home vector were greater in males with semidomes than males without semidomes. Our results strongly support the hypothesis that male fiddler crabs build structures for landmark homing. Key words: construction, fiddler crab, homing, orientation, visual landmark. [Behav Ecol]