A Warmer Earth Means No More Male Painted Turtles
The painted turtle is a freshwater turtle found throughout North American, from southern Canada to northern Mexico, from the Atlantic to the Pacific. But some time in the next 100 years, they might not be found anywhere. Scientists from Iowa State University who have studied the turtle’s nesting behavior for 25 years say that its survival could be threatened due to climate change.
The gender of a baby painted turtle is determined by the temperature at which its eggs are incubated, with warmer temperatures producing females and cooler ones, males. From studying painted turtles on a small island in the Mississippi River in Illinois, the scientists found that female turtles can lay their eggs as much as ten days earlier or later in response to changing environmental conditions.
With global temperatures predicted to rise by 4 to 6 degrees Celsius (7.2 to 10.8 Fahrenheit) over the next century, scientists created a mathematical model to see if laying eggs a few days earlier would be sufficient for both male and female baby turtles to hatch. What they discovered is that, even if temperatures rise only 1.1 degrees Celsius (1.98 Fahrenheit), “100 percent” of painted turtles born will be female by the end of this century.
Unfortunately, according to the scientists’ model, the situation for the turtles could actually be worse. The temperature is expected to rise so much that eggs will be killed before they even hatch.
As Discovery Magazine points out, painted turtles — who have evolved a “distinctive body design” that has not changed for some 210 million years — are unlikely to be able to adapt their ways to a world changing as quickly as ours is. While “some individual turtles may be able to adapt by laying their eggs in wetter or shadier areas… evolution doesn’t offer the turtles much hope.” Painted turtles have a lifespan of about a half a century and reach sexual maturity after many years. They are simply not able to “evolve quickly enough to deal with a warming climate.” The same dire scenario could also await snakes and reptiles who lay their eggs in the soil.
Scientists have recently sequenced the painted turtle’s genome, after several years of effort. From this, they hope to learn clues for its longevity and also its ability to go for long periods without oxygen, while hibernating in ponds covered in ice. Somehow, even with oxygen deprivation, the turtle is able to protect its heart and brain; studying the turtle could help scientists improve treatments for heart attacks or strokes in human beings. As Richard K. Wilson, director of Washington University’s Genome Institute, comments, painted turtles
…may be slowly evolving, but turtles have developed an array of enviable features. They resist growing old, can reproduce even at advanced ages, and their bodies can freeze solid, thaw and survive without damaging delicate organs and tissues. We could learn a lot from them.
It is all the more troubling that painted turtles, who are not yet considered an endangered species, could soon become one due to the irreversible effects of climate change.
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