Within-season nesting parameters
Within a single season, females laid, on average, 3.2 clutches. Field estimations based on the length of the nesting season and the observed inter-nesting interval proposed that each female laid on average 6 nests in 2017/18 (Touron et al., 2018). The true number is likely to lie between these two estimations and is coherent with clutch frequencies for other green turtle populations in the Pacific Ocean (reviewed in Pilcher 2021). They vary from 1.8 in French Frigate Shoal to 7 ± 1.3 clutches per female per season in the Northern Mariana Islands (Balazs, 1980; Summers et al., 2018). Additionally, through parentage analysis, 74 nests without observed females in the field were associated with a female, demonstrating the efficiency of the analysis to supplement field observations.
Inter-nesting interval was highly variable (between 0 and 94 days) and an interval of 11 to 14 days was the most common interval in this population. This is coherent with field observations (Touron et al., 2018), and aligns with findings in other populations (reviewed in Robinson et al., 2022). As not all nests could be analysed, the longest inter-nesting interval could not be determined. However, and more surprisingly, our study reveals the ability of females to lay regular-sized clutches within a very short interval (0 to 3 days). This represents a new finding in the reproductive strategy of green turtles. This shows a capacity for plasticity in nesting behaviour, a potential advantage in allowing a population to adapt to changing environmental and weather conditions on nesting beaches if one supposes that females might search for optimal nesting conditions. Plasticity in nesting behaviour has been observed in Tetiaroa, with an increase in the nesting season length over the years (Touron et al., 2018), possibly indicating that females may look to nest during cooler months to produce more male offspring in the ongoing warmer conditions (Laloë et al., 2020).
For almost all females, clutches were sired by the same father within a season, coherent with the fact that breeding occurs before nesting (Hays et al., 2022). However, one male (*129) sired 2 clutches in the middle of the nesting season, which induced multipaternity in these clutches. The genes of this male were not found in the first three clutches nor the last five clutches laid by the same female (CMY0188) during the season, although the number of sampled hatchlings (1 to 17) was enough to detect multipaternity in some of these clutches. The first clutch sired by this male was laid 40 days after the first recorded clutch for this female. Female marine turtles are thought to be available for reproduction only for a short interval of approximately one week, before nesting (Comuzzie and Owens, 1990). Here we suggest for the first time in a natural sea turtle population that mating occurs during the inter-nesting interval (but see Sakaoka et al., 2011, on a captive population of loggerhead turtles), and provide another indication that green turtles are capable of unexpected plasticity in their mating behaviour.