"If global warming continues on its current track, some turtles could once again migrate northward, while others would need to adapt to warmer temperatures or go extinct," says Jason Bourque, here with a 56-million-year-old shell of an  ancient tropical turtle. (Credit: Jeff Gage/Florida Museum of Natural History)

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Fossils show how heat might send turtles packing

As the earth got warmer 56 million years ago, tropical turtles migrated 500 to 600 miles north to escape the heat. But if today’s turtles try the same thing, they might run into trouble.

Turtle fossils found in Wyoming offer clues to how animals in the future might respond to future climate change.

While the fossil turtle and its kin were able to move northward with higher temperatures, human pressures and habitat loss could prevent a present-day migration—and might lead to the extinction of some modern species.

Move or go extinct

The wayfaring turtle, Gomphochelys nanus, was among the species that researchers believe picked up roots and moved during a temperature peak known as the Paleocene-Eocene Thermal Maximum. Lasting about 200,000 years, the peak resulted in significant movement and diversification of plants and animals.

“We knew that some plants and lizards migrated north when the climate warmed, but this is the first evidence that turtles did the same,” says Jason Bourque, a paleontologist at the Florida Museum of Natural History at the University of Florida and lead author of the study published online in the Journal of Vertebrate Paleontology.

“If global warming continues on its current track, some turtles could once again migrate northward, while others would need to adapt to warmer temperatures or go extinct.”

Journey roadblocks

The new turtle is an ancestor of the endangered Central American river turtle and other warm-adapted turtles in Belize, Guatemala, and southern Mexico.

These modern turtles, however, could face significant roadblocks on a journey north, since much of the natural habitat of these species is in jeopardy, says study coauthor Jonathan Bloch, a Florida Museum curator of vertebrate paleontology.

“If you look at the waterways that turtles would have to use to get from one place to another, it might not be as easy as it once was. Even if the natural response of turtles is to disperse northward, they have fewer places to go and fewer routes available.”

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To put the new turtle in evolutionary context, researchers examined hundreds of specimens from museum collections around the country, including turtles collected during the 1800s housed at the Smithsonian Institution.

The fossil history of the modern relatives of the new species shows they could be much more wide-ranging, if it were not for their restricted habitats, says coauthor Patricia Holroyd, a vertebrate paleontologist at the University of California, Berkeley.

The Central American river turtle is one of the most endangered turtles in the world, threatened by habitat loss and its exploitation as a human food source.

“This is an example of a turtle that could expand its range and probably would with additional warming, but—and that’s a big but—that’s only going to happen if there are still habitats for it,” she says.

Source: University of Florida

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