Turtles along the Mississippi River alter nesting dates due to rising temperatures

November 7th, 2008 - 3:41 pm ICT by ANI  

Washington, Nov 7 (ANI): A researcher from Iowa State University, US, has said that turtles nesting along the Mississippi River and other areas are altering their nesting dates in response to rising temperatures.

The researcher, who led the study, is Fred Janzen, a professor in ecology, evolution and organismal biology.

Janzen and his collaborators studied mud turtles, sliders, snapping turtles and painted turtles that live in South Carolina, Nebraska, and along the Mississippi River between Iowa and Illinois.

They studied turtle nesting habits and also accumulated research going back decades in order to track the habits of the turtles to find out when they make nests and lay eggs.

The results have been astonishing, said Janzen. In some cases such as regional populations of red-eared sliders, they are now nesting three weeks earlier than they did in the early 1990s. That is the fastest response to climate change of any species that I know of, he added.

According to Janzen, the turtles that changed their nesting habits were not only young turtles that are nesting for the first time, but were also older turtles that were changing their habits.

This trait, called plasticity, helps animals alter their behavior in the short term until inherited behavior takes over.

What we found was that in the late 1980s, painted turtles started nesting in early June, now it is on the order of 10 days or more earlier, said Janzen. These behaviors are showing how the plasticity of the species is helping them survive, but we are wondering what the limit is to their ability to adapt, he added.

An aspect of the study that surprised Janzen was the gender of the offspring.

The gender of turtle offspring, as with many reptiles, is typically determined by the temperature of the ground where they lay their eggs.

Janzen predicted that with warming temperature, the phenomenon of temperature-dependent sex determination would cause a disproportionate number of females since warmer conditions produce that gender.

But, just the opposite seems to be happening, with male babies outnumbering the females.

Warmth produces females, so we thought wed have more females, said Janzen. But what we think is happening is, since the air feels warmer, the turtles are nesting earlier. But the ground is still cold, so the cold ground is causing us to get more males, he added. (ANI)

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