Warm Sand and Sea Turtle Eggs

Sea turtle eggs do not get their sex only from genes. The temperature of the sand around each egg decides whether the hatchling becomes male or female.

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In the picture

Central egg in the warm nest core.
Orange-red sand beneath the central eggs.
Outer egg near the cooler nest edge.
Blue-tinted sand at the nest edge.

Examples

A sunny spot on a beach blanket feels warmer than a shaded spot under a parasol.
A tray of soil near a window stays warmer than a tray in a cool corner.

Key takeaways

In sea turtles, warmer sand around an egg usually produces a female hatchling, and cooler sand produces a male.
The temperature matters during incubation, so the sand around the egg is like a thermostat for sex.