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Shell disease challenges work to restore endangered western pond turtle

COLUMBIA RIVER GORGE — The two western pond turtles kept trying to swim in midair as wildlife biologist Stefanie Bergh detailed the differences between the healthy turtle and the one with shell disease.

For years, the Washington Department of Fish and Wildlife and its partners have been reintroducing young western pond turtles into the wild. On Tuesday morning, experts collected adult turtles suffering from shell disease — a mysterious, difficult-to-cure and sometimes fatal disorder.

Experts are in the midst of a three-year effort to learn the cause of the disease and how to prevent it by collecting, treating, and studying the affected turtles and the water they live in.

The program is focused on getting answers to open questions. Is it contagious? Is it hereditary? Does it affect reproduction? Is it curable?

At a location in Klickitat County, researchers placed 20 traps in three different ponds. Bergh and two volunteer interns from Oregon State University checked each trap during the morning session.

Not all the turtles they found were infected. As Bergh held two small turtles, she noted their health. “This is the whole goal,” Bergh said: “Healthy young wild turtles.” The healthy turtles’ shells look shiny and dark and feel hard and smooth. Other turtles with signs of shell disease look bleached and dull and felt soft and rough.

Treatment for the disease started in 2015, but it has been hard to tell how well it is working. The disease is slow growing, and turtles live a long time, so experts do not yet know if the surgery used as treatment is a cure.

“Turtles do everything slow,” said Bergh, who works for the Washington Department of Fish and Wildlife.

“The whole shell disease thing is pretty depressing,” she added.

The western pond turtle is a native freshwater turtle facing local extinction. Part of the conservation effort focuses on population numbers, but health is a major focus, as well. In 1980, there were only 150 western pond turtles. Now the population has grown to an about 1,000. That is a result of the efforts of the Washington Department of Fish and Wildlife and partners including the Oregon Zoo.

‘Head start’

The bullfrog, a nonnative predator that preys on turtle eggs and young turtles, played a major part in the turtle population’s decline.

Turtles leave their eggs in dry sand, leaving them vulnerable to predators, so since 1991, scientists have been covering the nests to give them a chance to hatch without being eaten.

After the turtles hatch, some are brought to the Oregon Zoo to live out the winter in a summerlike climate, giving them a chance to grow. Having spent their first winter in prime growing conditions, the young turtles are larger than a bullfrog’s mouth when released — an obvious help with survival.

Researchers say that most of the turtles with shell disease have been part of that “head start” program, though there are now a couple of strictly wild turtles that might be showing signs of the disease.

Because of all the variables in the turtle’s life, Bergh said, experts don’t know what causes shell disease. So now they are trying to control those variables and find the cause.

One solution to increasing the turtle’s population is getting rid of the bullfrogs.

“Eradicating bullfrogs is easier said than done,” Bergh said. But years of efforts at this site are starting to yield results. In addition to finding more wild born and grown young turtles, the local tree frog is starting to thrive again, too.

Bergh said that without the nonnative predator, the turtles do just fine in the wild.


Source: https://www.columbian.com

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