Sex ratios of two species of sea turtle nesting in Suriname

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Abstract
The green turtle (Chelonia mydas) and the leatherback (Dermochelys coriacea) nest on the same beach in Suriname. For both species there are seasonal changes in the sex ratio of the hatchlings, with more males being produced during the wetter cooler months of the nesting season and more females during the drier warmer months. This shows that temperature determination of sexual differentiation has considerable demographic consequences in natural circumstances. Leatherbacks require slightly higher (ca. 0.5 °C) temperatures for female differentiation than green turtles and leatherbacks nest in relatively greater numbers during the warmer parts of the season. Estimates of overall sex ratio for hatchling green turtles (53.9% female) and for leatherbacks (49.0% female) were obtained by multiplying sex ratio and nesting frequency for different portions of the season. These estimates are tentative because there were differences between different years both in sand temperatures on the beach and in nesting distribution. Also discussed are the problems in assessing parental investment in the two sexes when the direction of sexual differentiation is determined after parental investment ends.