Wood Turtle (Glyptemys insculpta)
As its scientific name, Glyptemys insculpta, implies, the shell of the wood turtle is one of the most ornate of the turtles in Michigan. A noticeable keel running down the back of the carapace and the pointed edges of the scutes along the back edge add to its sculpted appearance. The yellow on the underparts of its neck, legs, and stomach, plus the highly visible deep circular growth rings of the scutes on the brownish carapace help with identification. The adult carapace length is 6.3 to 9.4 inches (16 to 24 cm).
Photo © Jim Harding
Wood turtles live in rivers with sandy-bottomed streams and rivers. They spend most of their time in the river from September to May, but in summer can be found foraging in woods, swamps, and meadows in the upland areas edging the stream or river. Logs or banks near water and sunny woodland openings are often utilized for basking.
These turtles are omnivores eating a variety of plants and animals and carrion found in and along the river. Wood turtles employ a unique technique to hunt earthworms. Using either an alternating foot stomp, or by lifting and dropping its shell on the ground, they create vibrations in the ground. These vibrations will cause earthworms to surface where they are quickly snatched for a meal. Anglers seeking bait can employ a similar technique. A stick stuck in the ground and wiggled back and forth to create vibrations will cause earthworms to leave the ground.
Egg-laying occurs in the sunny areas of exposed river sand banks. Females lay 3-to-18 soft-shelled eggs in a cavity they dig in late-May or June. After about six weeks of incubation in the warm sand, brownish, long-tailed nestlings hatch and head to the water. It may take as many as 20 years before these new hatchlings begin to produce offspring of their own.
The population of wood turtles in Michigan has declined in recent years and is considered rare in the northern Lower and Upper Peninsulas. It is protected by Michigan law as a special concern species. Threats include predation by raccoons and skunks. In some areas, egg and hatchling mortality can exceed 80 percent. Water pollution and sedimentation can impact survival of turtles. Reduction of nesting areas through stream bank stabilization has impacted turtle populations in local areas. The commercial pet trade and removal of individual turtles for personal pets has also reduced populations.
The future for this relict of the time of dinosaurs is uncertain, but finding solutions to a number of the threats is important in making sure the wood turtle remains part of Michigan's Wildlife Heritage.
Clemmys insculpta (University of Michigan, Museum of Zoology)
Glyptemys insculpta (NatureServe)
Wood Turtle Occurrences Map