“Wood turtles, like trout, don’t like ugly places, and we need them as part of a healthy, functioning ecosystem,” said Tom Akre, a research ecologist at the Smithsonian’s facility in Front Royal, Va. “They matter because they’re important indicators of our environment, and their presence — or absence — lets us know if there’s clean water and clean air.”

Wood turtles lost a lot of their habitat as the streams where they’re typically found have became polluted with runoff from agricultural uses or overrun by nearby development, experts said.

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In Virginia, experts said, wood turtles have “lost nearly half of their historic range,” and they’re considered “one of the most endangered freshwater turtles in North America.”

Akre’s team plans to look for wood turtles in Rock Creek Park in the District by using what’s called “environmental DNA” to find how many of them remain. Because their population there may be low — and they’re hard to see in murky water — researchers take water samples and then filter them at a lab where DNA is extracted to see if it matches that of a wood turtle.

“We’re essentially using crime scene-like technology as markers to detect them,” Akre said.

Researchers have put GPS and radio transmitters on wood turtles they’ve found in northwest Virginia so they can better understand how far they travel, especially when searching for a mate. In a few cases, they have found instances of wood turtles crawling roughly 15 miles over mountains in northwest Virginia and neighboring West Virginia to look for new streams and mates.

Finding turtles is no easy task. They live under leaves in brown, cloudy water. Researchers have to step carefully in stream beds. Once they find a turtle, they assign it a number and put notches on its shell to identify it and track it over time. They also take note of its length, width, height, weight, and any unique markings on its shell before putting it back into a stream.

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It is illegal to harass or possess wood turtles. The public should not disturb them and only watch them from a distance, experts said. Smithsonian researchers are allowed to conduct wood turtle surveys under state research permits, and they’re trained to handle them carefully with minimal disruption to their habitats.

Adapting to a changing environment has been one of the biggest challenges for wood turtles. Bald eagles, for example, have made a resurgence in many areas, including in the D.C. region, as they’ve made their homes in more urban, suburban populated areas. But for wood turtles, it is not the same.

“Relative to most mammals and birds, everything wood turtles do is slow,” Akre said. “They grow slowly, and they reproduce slowly.”

Akre said it takes, on average, 15 years for a wood turtle to grow and mature to be able to reproduce. “So the fastest an offspring could mature and lay eggs would be about 30 years after its mother hatched,” he said.

But because the “survival of eggs, hatchling and juveniles is so low, it can actually take much longer for an average female wood turtle to replace itself with a mature and reproducing daughter,” Akre said. “By the time an average hatchling reaches maturity and successfully reproduces an offspring that survives to successfully reproduce offspring, it could be closer to 60 years.”

Akre said hatchling wood turtles are sometimes called the “M&Ms of wildlife” because they’re “small, brown and easy to eat,” making them easy prey for raccoons, herons, crows, skunks and foxes.

Experts said they believe that wood turtles still thrive in roughly 30 to 40 streams in the D.C. region but lost a large portion of their habitat long ago.

In Virginia, Akre said, all of their habitat along the Potomac River in parts of Fairfax and Loudoun counties has nearly disappeared. In Maryland, experts said, the wood turtle population has lost roughly one-third to one-half of its range and is now found mostly just in the western part of the state.

By tracking where the turtles are, Akre said, researchers can protect their landscape for better survival.

“If we don’t track them and understand them,” Akre said, “then there’s a potential they might not be around.”