Effects of multiple paternity on immediate reproductive and hatchling outcomes for loggerhead turtles (Caretta caretta) nesting at Yakushima Island, Japan: a common beach hatchery experiment

Polyandry, where a female mates with multiple males, sometimes results in multiple paternity, the presence of several sires within a single brood, and is observed across various taxa. The potential benefits of this phenomenon for female sea turtles are a subject of ongoing discussion. This research aimed to determine if the reproductive and hatchling traits of loggerhead turtles ( Caretta caretta ) are enhanced by a greater number of sires estimated per clutch. Clutches were incubated at a common beach hatchery in Yakushima Island, Japan, in two separate nesting seasons. Twenty-six or 28 females and their 291 or 401 offspring were genotyped at three or at ≥ three of five microsatellite loci to estimate the number of sires per clutch using two programs, respectively. GERUD estimated 21 singly and five multiply sired clutches, whereas COLONY estimated 15 singly and 13 multiply sired clutches. Although singly sired clutches had significantly higher success of fertilization, hatching, and emergence than multiply sired clutches in the GERUD dataset, opposite trends were shown in COLONY. However, the estimated number of sires per clutch was not significantly correlated to these three parameters in both programs. Female straight carapace length, clutch size, and means and variation for hatchling morphology were not significantly different between singly and multiply sired clutches and were not significantly correlated to the estimated number of sires per clutch in both programs. These results suggest that female loggerheads in this rookery do not gain direct and indirect genetic benefits immediately from multiple paternity. • Whether multiple paternity is beneficial to female sea turtles is controversial. • I examined the effects of multiple paternity on female loggerhead turtles. • Clutches were incubated at a common beach hatchery in Yakushima Island, Japan. • Fitness estimators did not obviously increase with the number of sires per clutch. • Females in this rookery do not benefit immediately from multiple paternity.