Experimental evidence for a seasonal shift in the strength of a female mating preference

The costs and benefits of mate choice can vary both spatially and temporally. Phenotypic plasticity in mate choice, which could be due to changes in choice criteria (e.g., acceptance thresholds) or shifts in underlying mating preferences (i.e., relative values assigned to different males), can therefore increase reproductive success. We examined shifts in female mating preference for male claw size between 2 seasons (winter and summer) in the fiddler crab Uca mjoebergi. We used custom-built robotic crabs in 2-stimulus mate choice experiments conducted in the field. Females showed a consistent preference for larger claw size, but this was significantly weaker during winter. This seasonal difference was observed for 2 successive years. We propose that the change in female preference for claw size is due to a seasonal difference in the value of a larger burrow, which strongly influences burrow temperature. Burrow temperature largely determines larval development rate and larvae release in fiddler crabs is constrained to a narrow time window where survival is optimal. Females appear to alter their preference for burrow width, which is signaled by claw size, between winter and summer, potentially allowing them to optimize developmental time of larvae and/or to reduce mate search costs.