For species of conservation concern, knowledge of key life-history and demographic
components, such as the number and sex ratio of breeding adults, is essential for accurate
assessments of population viability. Species with temperature-dependent sex
determination can produce heavily biased primary sex ratios, and there is concern that
adult sex ratios may be similarly skewed or will become so as a result of climate
warming. Prediction and mitigation of such impacts are difficult when life-history
information is lacking. In marine turtles, owing to the difficultly in observing males at
sea, the breeding interval of males is unknown. It has been suggested that male breeding
periodicity may be shorter than that of females, which could help to compensate for
generally female-biased sex ratios. Here we outline how the use of molecular-based
paternity analysis has allowed us, for the first time, to assess the breeding interval of
male marine turtles across multiple breeding seasons. In our study rookery of green
turtles (
Chelonia mydas
), 97
%
of males were assigned offspring in only one breeding
season within the 3-year study period, strongly suggesting that male breeding intervals
are frequently longer than 1 year at this site. Our results also reveal a sex ratio of
breeding adults of at least 1.3 males to each female. This study illustrates the utility of
molecular-based parentage inference using reconstruction of parental genotypes as a
method for monitoring the number and sex ratio of breeders in species where direct
observations or capture are difficult.