What process determines whether many sea turtle hatchlings develop as male or female?

Temperature-dependent sex determination determines whether many sea turtle hatchlings develop as male or female.

In many sea turtles, the temperature of the developing eggs during a critical part of incubation influences sex. Warmer nest temperatures generally produce more females, while cooler temperatures generally produce more males, although the exact pattern varies among species.

This differs from the familiar system in humans, where sex is determined by chromosomes at fertilization. Sea turtle eggs do not receive a sex chromosome from the mother or father that directly fixes the hatchling’s sex in the same way.

Nest depth, shade, sand color, rainfall, and climate can therefore affect the sex ratio of a nesting population. Temperature does not change the sex of a fully developed hatchling; it acts during embryonic development. Sea turtles also show species-specific differences, so the pattern should not be treated as identical for every turtle species.