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From invasive weeds to flooding, the wood turtle is under threat in Vermont

From invasive weeds to flooding, the wood turtle is under threat in Vermont

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Until spiny softshell turtles are endangered in Vermont and spotted turtles are endangeredforest tortoises may soon be endangered in the state due to land use change. That’s why the state Department of Fish and Wildlife closely monitors the species before more serious intervention is needed.

The loggerhead turtle, a medium-sized reptile native to Vermont, is known for its bright orange neck and inner legs, creating a unique, easily recognizable pattern. This model also led to an increase in demand for of caught turtles on the international black market.

But this is not the only threat to these reptiles. Invasive species such as the Japanese knotweed are a major threat because they fill the sand and gravel bars where wood turtles normally lay their eggs. Besides, repeated flooding in Vermont caused flooding of eggs, and as this species has a low reproductive rate, this could seriously affect the local population.

These threats have forced the department to define forest turtles as the species most in need of conservation in Vermont.

On Tuesday afternoon, two wildlife conservationists waded through cool, rushing streams and crossed muddy riverbanks in central Vermont to conduct one of the last wood turtle surveys of the season.

Kylie Briggs, Director of Conservation Orian Societya nonprofit organization that focuses on protecting and restoring habitats for rare reptiles and amphibians, and Molly Parren, a turtle technician with the Vermont Department of Fish and Wildlife, got out of their pickup truck to put on their boots and waders. Briggs retrieved his antenna and radio telemetry from the pickup.

“With radio telemetry (first), we attach a small transmitter to the turtle,” Briggs said. “The transmitter sends out a radio signal, which essentially makes a sound, and then we use an antenna and a receiver to determine where that sound is coming from, and then we follow it until we find where the turtle is.”

Kylie Briggs and Molly Parren find a wood turtle using radio telemetry. Photo by Clara Bouters/VTDigger

Briggs collects baseline data — preliminary data that allows biologists to determine where hot spots are for turtles and their populations in those locations.

Vermont’s streams provide ample habitat for loggerhead turtles, but their ability to nest and develop populations is becoming increasingly difficult, Briggs said. As the invasive Japanese knotweed spreads, female turtles are forced to travel further in search of suitable nesting sites, further threatening the survival of the species.

“We only get turtles 40-50 years old and no turtles over 20 years old. That tells us, ‘Here’s a problem that needs to be solved at this site,'” Briggs said.

Because of the longevity of tree turtles—some can exceed 80 years—as well as their low reproductive rates and slow maturation, their populations are vulnerable to any threat that kills adults or removes them from the population.

“They don’t start laying eggs until they’re in their 20s, so it takes a long time for the population to replace them,” Briggs said.

Wood turtles spend time in water and on land, but prefer to nest in river valleys — which are also the best places for farms and the easiest places to build roads, Briggs said. When wood turtles spend time on land, they can be killed by tractors or run over by cars.

“Cars are a problem for all of our turtles, but especially for wood turtles, and I’ve lost turtles that have been run over by farm equipment,” Briggs said. In some cases, the loss of just one or two wood turtles per year due to humans can lead to significant population decline or extinction, according to The Orianne Society.

But preserving wood turtle habitat can benefit landowners. Federal programs in the US Farm Bill offer financial assistance to landowners and farmers who establish riparian buffer zones.

After walking along the stream, Briggs, wearing polarizing glasses in knee-deep water and carrying an antenna, found the turtle. It was under the river bank, too far to grab, so he moved on. After crossing the stream twice more, more than an hour later, Briggs found a new wood turtle in the stream that he had not yet tagged.

Both Parren and Briggs were thrilled to find the new, apparently juvenile turtle, and immediately began logging its details, including weight and length, into an online form on Briggs’ phone.

“In forest turtles, in males, the lower part of the shell is concave, this is a male trait. Like females, the bottom of the shell is flat,” Briggs said. “In terms of age, we can count the growth rings on their shells, just like counting the rings of a tree.”

The newly discovered turtle was about 15 years old. Wood turtles grow for the first 15-20 years of life, but can live up to 50-70 years. As they age, their shells gradually wear down and become smoother, which is how biologists estimate their age. The lighter yellow tissue in the center of the turtle’s shell indicates that it is still growing, Briggs said.

“It’s rare to see a new young turtle at this location,” he said, as the location is prone to severe summer flooding. “The biggest concern now is that if we have frequent summer floods (for) many, many years, it could be too much flooding for the population to survive.”

However, at one site where the dam causes frequent summer flooding, nearly all the turtles chose to lay their eggs in the upland, safely away from the river, Briggs said.

“I wonder if that’s what they responded to,” Briggs said. “The turtles know that the site floods often, but that’s just my interpretation of their behavior there.”