Small males of the fiddler crab Austruca perplexa court more in the off-peak breeding period when large males court less.

Many animals adjust their reproductive investment in line with their current competitive abilities. High-quality individuals may breed in the peak breeding period because they have a greater probability of finding high-quality mates, whereas low-quality individuals may breed in the off-peak period to avoid competing with high-quality rivals. We observed a wild population of the fiddler crab Austruca perplexa to investigate the waving rate of large and small males towards large and small females in the peak and off-peak breeding periods. We predicted that large males would invest more in courtship in the peak breeding period and invest less in the off-peak period, whereas small males would invest more in courtship when large males invest less. It was observed that large males waved their major claws more frequently in the peak breeding period than in the off-peak period and waved more towards large females, while small males waved more in the off-peak breeding period and their waving rates were not different towards large or small females. For small males, investing more in courtship in the off-peak breeding period may offer a greater probability of acquiring females than competing against large rival males in the peak breeding period. [ABSTRACT FROM AUTHOR]