Once upon a time, the wood turtle was the most common freshwater turtle in eastern Massachusetts. Today it is in severe decline. Naturalists Louis Agassiz and Henry David Thoreau documented their observations of this reptile in the mid-1800s.
But these turtles have been around for thousands of years. Glacial advances pushed the wood turtle south to what is now Georgia and Tennessee. After the glaciers retreated 10,000 years ago, these turtles repopulated North America from Nova Scotia in the north to Virginia in the south and as far west as Minnesota.
In the 1850s, Agassiz collected, studied and documented wood turtles in Lancaster, Mass. He collected more than “one hundred in an afternoon.” Some of his collection is in Cambridge at Harvard’s Museum of Comparative Zoology’s Herpetology collection, which is not on public display.
Credit: Jeanine Farley; Museum of Comparative Zoology, Harvard University; (c) President and Fellows of Harvard College
Today’s wood turtle (Glyptemys insculpta) is six to eight inches long, about the length of a cell phone, and lives in fresh water. People disagree on how it got its name, with some saying its shell looks like a carved piece of wood, others because it is often found in wooded habitats. The scientific name glyptos is from Greek meaning “carved” or “engraved” and emys means “turtle.” Insculpta is Latin for “sculptured” or “chiseled.” So, the literal meaning of Glyptemys insculpta is “sculptured carved turtle.” It has another unique feature, too, which has given it still another nickname: redlegs. You can probably figure out why it is called by this moniker.
At about the same time that Agassiz collected these turtles in Lancaster, Thoreau encountered “a great many wood turtles on the bank of the Assabet” in 1858. He wrote about finding a wood turtle “on its back with its head and feet drawn in and motionless, and what looked like the track of a crow on the sand. Undoubtedly the bird had been pecking at it, and perhaps they get many of the eggs.”
The abundance of turtles in the past and the lack of them today is evident in a 2019 study where researchers conducted 25 half-day surveys of wood turtles in Lancaster and found only 29 individuals.
Agassiz and Thoreau might have some trouble recognizing the animals today, as modern females are 16 percent larger and males 24 percent larger than their 1850s ancestors. Wood turtle body size is linked to temperature, with warmer temperatures leading to larger young turtles. These results may suggest that temperatures in the 1850s were cooler than they are today. But greater population density in the 1850s may have increased competition for food, making the turtles smaller. There could be other reasons for this size discrepancy, including more European earthworms for turtles to eat today or changes in forest cover or water nutrients.
Speaking of earthworms, wood turtles employ a unique foraging behavior known as worm stomping. The turtles alternate stomping their front feet on the ground, one stomp per second, which causes earthworms to surface, only to be quickly devoured by the waiting turtles. Some people think the stomping resembles raindrops hitting the ground. Others say the stomping makes the worms think a mole is digging after them. Still others think the stomping disturbs the leaf litter, soil and tunnels where they live, forcing the worms to the surface.
There are other signs of wood turtle intelligence. In 1932, psychologist O.L. Tinklepaugh placed a wood turtle in a complex maze with food at the end. It took the hungry wood turtle only four tries to complete the maze without any mistakes. This exceptionally quick spatial learning was comparable to what would be expected from a rat in the same maze (we all know how difficult it is to keep clever rats out of our trash barrels and dumpsters). Tinklepaugh concluded that the wood turtle’s reputation for “stupidity” was undeserved.
Wood turtles are active from spring until fall. The turtles hibernate (brumate) until March or April. Unlike some turtles, wood turtles cannot tolerate long periods without oxygen, so they overwinter in flowing, oxygenated water, hidden in deep pools or under banks or logs.
Females have to be at least 15 years old to reproduce. Mating happens in the fall, and a female will often mate with more than one male. She’ll store the sperm over the winter or even longer. In June, she is ready to produce and lay about seven eggs. She will find sandy soil in an elevated area that won’t flood, often returning to the same nesting site year after year. After laying her eggs, she covers them with dirt and leaves, then deserts them. The eggs incubate on their own for a few months and hatch in late August or September. Most of the newborns do not survive. Over her lifetime, a female produces only a few hatchlings that make it all the way to adulthood. Those that do live a long time — 40 to 60 years.
Today, the wood turtle is endangered. In the 170 years since Thoreau watched them nesting, roads, development, agriculture and other changes have made life difficult for this unassuming turtle that takes so long to reach sexual maturity. In addition, suburban predators like raccoons, coyotes, and foxes led to increased predation of turtle eggs and hatchlings.
The wood turtle has survived glaciers, predation and thousands of New England winters. Time will tell if it will survive another 170 years.
A stronger
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