In sea turtles, what environmental factor commonly determines hatchling sex?

In sea turtles, incubation temperature commonly determines hatchling sex.

This system is called temperature-dependent sex determination. For many sea turtles, warmer nest temperatures produce a higher proportion of females, while cooler temperatures produce more males. The pivotal temperature differs among species and populations, so there is no single temperature that applies to every nest.

Because nests warm and cool with weather, sand conditions, shade, and climate, temperature can strongly influence local sex ratios. Researchers study these patterns using nest thermometers, hatchling observations, and long-term monitoring. Sea turtles do not generally have sex chromosomes that function like the familiar human XX and XY system.

The relationship is not an absolute rule for every reptile or every species. Crocodilians and some lizards also show temperature-dependent sex determination, but their temperature patterns can differ. Sea-turtle conservation projects sometimes shade nests or move eggs to manage extreme temperatures.