MATE ACCEPTANCE AND GUARDING BY MALE FIDDLER-CRABS UCA TETRAGONON (HERBST)

The fiddler crab, Uca tetragonon (Herbst) mates both on the surface ne ar female-defended burrows and underground in male-defended burrows. I n underground mating, which requires relatively high male investment, males attract both non-ovigerous and ovigerous females into their burr ows by claw waving. Males aggressively expel some females soon after t hey enter their burrows and others after pair formation, but before fe males spawn. Finally males guard some females in their burrows until t hey spawn, which presumably ensures paternity. Males do not select mat es of a particular body size, but they do differentially accept female s with late-stage eggs, those about to release larvae and spawn anothe r clutch. Except at the beginning of the reproductive season, few ripe non-ovigerous females are available because females spawn successivel y and only in moderate synchrony. By differentially accepting late sta ge ovigerous females, males may increase their fertilization rates bec ause they minimize the time they spend guarding each of their mates to ensure their paternity. A male-biased operational sex ratio and a hig h last male advantage in sperm competition are two conditions that may have favored male choice based on female guarding time in this specie s.