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Desert Diary

Reptiles/Turtle Sex


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Many of us know that it's the man who genetically determines the sex of a child, and not surprisingly, we assume that's the case for everything. Alas, things aren't so simple in nature! Among birds, it's the female. But that's not the end of it. Some fish even change their sex according to their place in the social hierarchy or for other reasons. And let's consider turtles.

The Spiny Softshell Turtle, a freshwater, aquatic animal present in our Chihuahuan Desert waterways, is one of the few turtles to have its sex genetically determined. In most turtles, sex is set by the temperature at which the eggs are incubated. Even this is not simple. Three patterns are known among turtles: in one, higher temperatures result in a high frequency of females while in another, a high frequency of males. In the third pattern, high and low temperatures result in females and intermediate temperatures in males. In humans, sometimes we talk of a pregnant woman having one in the oven—somehow, this seems much more appropriate for turtles.

pen and ink

Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.

Western Box Turtle

Western Box Turtle (Terrapene ornata). Photograph by Carl S. Lieb.



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Web Resources

The Role of Estrogen in Turtle Sex Determination.

Turtles and Global Climate Change.