To researcher Jim Harding, spending nearly a lifetime studying wood turtles just makes sense. “These are very long-lived animals,” Harding said. “And if you want to understand them, you have to study them over a long period of time.”
An instructor and outreach specialist with Michigan State University’s Zoology Department, Harding has been studying the wood turtle population along a river in Michigan's Upper Peninsula since 1969, when he was working on his master’s degree. But, he’s quick to tell you, he’s been interacting with them even longer; he has a photograph of himself and a turtle from his study site – on property owned by his grandfather – when he was five years old.
“I was always fascinated by turtles,” he said. “It wasn’t until many years later that I realized these weren’t just any turtle. They were special.”
The wood turtle is one of 10 species of turtles that live in Michigan. Of the 10, one species is considered threatened (spotted turtle) while the wood turtle joins the box turtle and Blanding’s turtle as a species of concern, explained DNR fisheries biologist Tom Goniea, who oversees reptiles and amphibians as coordinator of the state’s Scientific Collector’s Permit program.
Wood turtles join Blanding’s and box turtles in a group of turtles that are unusually long-lived, Harding said. Wood turtles have unfortunately been attractive to the pet trade, due to their ornate, ridged shells that look like carved wood; their striking, brightly colored yellow bodies; and their similarities to tortoises, which seems to lead people to believe wood turtles are more intelligent or wiser than other species of turtles.
Wood turtles are associated with moving water, from small creeks to large rivers. Although Harding finds them upland at times, “you never find them too far from the river,” he said.
The population on his study site is “just a shadow of its former self,” Harding said, something he attributes to two causes: collection by the pet trade back in past decades and a burgeoning raccoon population.
“For years we’ve had no evidence of natural reproduction at all,” said Harding, who recently spent time with several associates looking for wood turtles – and their nests – on his study site. “We don’t see any juveniles. The raccoons are getting all of their nests.”
As a result, Harding – who has the appropriate permits from the DNR – has taken to “head-starting” wood turtles: If he finds a turtle nest, he collects the eggs, incubates them, and raises the hatchlings for a year, then releases them at the study site.
By head-starting the young turtles, they are able to reach the size of a three- or four-year-old by the time Harding releases them, which he hopes will lead to better survival rates, even with some loss of adult turtles to raccoons.
Raising the hatchlings for a year is more of a chore than it sounds; the eggs are delicate and must be handled with care. The juveniles must be kept in separate holding areas as they’ll bite each other’s tails and limbs if left together.
To accommodate the hatchlings, Harding raises a few himself, has help from some fellow turtle aficionados with a couple more, and enlists the aid of John Ball Zoo in Grand Rapids for help with the rest. So far, his work appears to be bearing fruit as he’s found some of his released turtles surviving in the wild.
Omnivorous creatures that have developed a unique hunting technique – they thump the ground with their shells, creating vibrations that send earthworms to the surface – wood turtles are in short supply across their home range, which extends west to Minnesota, north into Canada and southeast to perhaps Virginia. In Michigan, wood turtles are found across most of the U.P and northern half of the Lower Peninsula.
“Michigan may be one of the states that is very important to their future because we have habitat,” Harding said. “They use a mosaic of forest and more open terrain. Timber harvests don’t bother them. Wood turtles do not require wilderness. All they require is that they be left alone.
“They live long lives because, even under the best of conditions, most of their eggs and young are destroyed,” he continued. “So few of them grow up, they have to lay eggs over 30 or 40 years in hopes that they can replace themselves. Every individual is valuable.”
Harding can’t tell you how long they live, but he has one specimen that he marked when the turtle was at least 20 years old and subsequently observed 45 years later, making the creature at least 65. “I suspect they can live a lot longer than that,” he said.
Wood turtles lay five to 18 eggs with an average clutch size of around 10. The turtles nest on sand banks that are large enough that they can get above typical high-water stages so the nests are not drowned out by floods. Harding said he “used to find dozens of clutches of eggs,” but these days, if he finds five or six nests “it’s a really good year.”
“I’m happy finding any,” he said. “Some years I’ve gotten skunked.” If a hiker or paddler encounters a wood turtle, they are advised to enjoy the sighting but then to move on.
“It is illegal to collect, possess, kill or otherwise harass or harm wood turtles or any other species of special concern,” Goniea said. Except for possibly helping one across a road, observers should keep their hands to themselves. And that will serve wood turtles splendidly, Harding said. “All they ask is to be left alone” he concluded.