Determination of sexual size dimorphism (SSD) in marine turtles is challenging because females are observed on nesting beaches, while males remain at sea and are rarely encountered. Data obtained from a sea turtle bycatch survey and a nesting monitoring program conducted in the same area in the Republic of the Congo give access to the body size of both male and female olive ridleys ( Lepidochelys olivacea ). Curved carapace length (CCL) in male and female olive ridleys reveals SSD, with males being larger than females. This large male SSD contrasts with the female-biased or absence of SSD commonly observed in sea turtles. The ultimate and proximate mechanisms potentially at play are discussed here and tested where possible. One of the main drivers of smaller female SSD could be egg production. We show that egg production in olive ridleys in the Congo is optimal for intermediate female CCL when corrected to nesting date. When females are longer, egg production decreases, probably because of the constrained three-dimensional volume. This counterintuitive relationship between CCL and egg production could be the driving force behind the unusual evolution of larger male SSD in olive ridley turtles, and ultimately, the small size of this species as compared to other marine turtles.

中文翻译：

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橄榄雷利海龟不寻常的两性异形和成年体小与体积几何约束有关

确定海龟的性别大小二态性 (SSD) 具有挑战性，因为在筑巢的海滩上观察到雌性，而雄性则留在海上并且很少遇到。从海龟兼捕调查和在刚果共和国同一地区进行的筑巢监测计划获得的数据可以了解雄性和雌性橄榄海龟（ Lepidochelys olivacea ）的体型。雄性和雌性橄榄树的弯曲背甲长度 (CCL) 显示 SSD，雄性大于雌性。这种大型雄性 SSD 与海龟中常见的雌性偏向性或缺乏 SSD 形成对比。此处讨论了可能起作用的最终和近似机制，并在可能的情况下进行了测试。较小的女性 SSD 的主要驱动因素之一可能是产蛋量。我们表明，当校正到筑巢日期时，刚果橄榄树的产蛋量对于中间雌性 CCL 是最佳的。当雌性较长时，产蛋量会减少，这可能是因为三维体积受限。CCL 与产蛋量之间的这种违反直觉的关系可能是橄榄海龟雄性 SSD 异常进化的驱动力，最终，与其他海龟相比，该物种的体型较小。