Variation in the Boldness of Courting Sand Fiddler Crabs (Uca pugilator)

TLDR: Within- and between-individual variation in the boldness of courting male sand fiddler crabs, Uca pugilator, is examined across an entire breeding season at a South Carolina (USA) salt marsh where courtship is restricted to supratidal embankments.

Abstract: Individuals can express boldness in their readiness to resume courtship signaling following a perceived threat. The degree of boldness that is selectively favored depends on the magnitude of costs and benefits that may vary across time and space. We examined within- and between-individual variation in the boldness of courting male sand fiddler crabs, Uca pugilator, across an entire breeding season at a South Carolina (USA) salt marsh where courtship is restricted to supratidal embankments. Boldness was assessed by the time to re-emergence and the number of re-emergences of males who were purposely startled into their breeding burrows once every 3 min for a total of five times. The two measures of boldness were significantly positively correlated. Courting males are on average bolder when their density is high and when tidal conditions correspond to peaks in the number of females moving over the embankment surface. Time to re-emergence increases with successive startles although some males consistently re-emerge faster than others. Large males are not bolder than small males. When male density is high, nearest neighbors frequently re-emerge at the same time, suggesting that males cue on the responses of other nearby males, perhaps by assessing substrate vibration. This may reduce the chance of losing a potential mate to a local competitor.