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UF study shows turtle species still suffering from past harvesting

This large female northern map turtle, Graptemys geographica, was captured in the North Fork of White River in Ozark County, Missouri in 2004. (Amber Pitt)
This large female northern map turtle was captured in the North Fork of White River in Ozark County, Missouri in 2004. (Amber Pitt, courtesy of UF News Bureau)

In Ozark County, Mo., a three-mile stretch of the White River once served as a home for the northern map turtle. The species swirled through the free-flowing stream and basked in the sun on the river bank.

After locals began reporting people harvesting the reptiles for food between the 1960s and 1980s, its population was devastated.

Max Nickerson, herpetology curator at the Florida Museum of Natural History, studied the species in 1969, snorkeling alongside the creatures. He tagged them and recorded them with Amber Pitt, a a Clemson University postdoctoral research fellow who studied river turtles as a University of Florida graduate student.

When Nickerson and Pitt returned more than a decade later, about 50 percent of the reptiles were nowhere to be found.

“We knew immediately in 1980 when we got into the river that something was wrong,” Nickerson said.

There was a substantially smaller amount of females and small turtles, Nickerson said, which suggested that within just 12 years of research, turtle harvesting had caused considerable population damage.

“The males, a good sized one is 120 grams,” Nickerson said. “The females, a good sized one is 1,200 grams, so someone harvesting for food is not going to harvest the males.”

Nickerson and Pitt returned to the site in 2004 to continue their research and see if the population had bounced back, but the damage was deemed irreversible.

Though a different species, the red-eared slider, seemed to have increased its population within that area of the river, the northern map turtles’ population in the area remained meager.

The 2004 examination of the river also revealed apparent habitat degradation over the years, with increased siltation, sedimentation and algal blooms in the area. Human recreation, which increased in the area since the 1980 study, can cause this damage.

Aside from river and water damage, swimmers and boaters can also scare the turtles, which prevents them from basking as much as they healthily should.

“This was an entire community that we were looking at,” Nickerson said. “(The) map turtle is threatened in most of its range, and all of the turtles within the genus are protected to some extent.”

Nickerson and Pitt published the study on Sept. 14 in Volume three of Copeia, a publication pertaining to fish, reptiles and amphibians.

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