Operational sex ratios (OSRs) are a key measure of population viability, shaped by reproductive dynamics such as breeding periodicity. In marine turtles, temperature-dependent sex-determination raises concerns about population viability, as rising temperatures bias hatchling sex ratios toward females. Male breeding periodicity may mitigate this imbalance by influencing OSRs at breeding sites, but direct monitoring at these sites can be challenging.
Flatback turtles (Natator depressus) are an endemic species with limited data on male reproductive patterns. Yawuru Nagulagan Roebuck Bay is a foraging ground that supports adult male and female flatback turtles from multiple genetic stocks, providing a rare opportunity to assess male reproductive patterns in this species. Since 2017, data from sightings (n=363), captures (n=196), and satellite tag deployments (n=28) have allowed us to define breeding patterns for male and female flatback turtles, and estimate OSRs based on breeding probabilities.
Our results indicate that males depart earlier and have shorter remigration intervals than females, suggesting sex-specific reproductive demands not previously documented in this species. Moreover, male reproductive cycles could buffer against hatchling feminisation and stabilise population dynamics. By refining our understanding of OSRs, we can better predict thresholds for, and guide conservation efforts to support population viability.