Girls Only

Climate change could push painted turtles toward heavily-female populations, a new study suggests.

A painted turtle’s sex depends on the temperature during its development. If the environment is warmer, the turtle tends to become a female; if cooler, it tends to become a male. So scientists worry that males could become more and more sparse with global warming, eventually driving the species extinct.

One possible escape route is that female turtles could start nesting earlier, when the weather is cooler. But it’s not clear whether this change would be enough to save the species.

A research team developed a model to test this scenario. If the region warmed by 4 degrees Celsius, the females could keep the soil temperature at the beginning of nesting the same by laying their eggs about three weeks earlier. But during the phase when the young turtles’ sex is determined, the temperature would still climb to 3.2 degrees Celsius higher than normal.

This trend would eventually result in “a 100% female sex ratio and ultimately population extinction,” the team writes in The American Naturalist. The turtles might have to adopt other measures to produce males, such as nesting in shadier spots. Roberta Kwok | 1 April 2013

Source: Telemeco, R.S., K.C. Abbott, and F.J. Janzen. 2013. Modeling the effects of climate change-induced shifts in reproductive phenology on temperature-dependent traits. The American Naturalist doi: 10.1086/670051.

Image © Gerald A. DeBoer |