Wood Turtles Don’t have it Easy in Wisconsin
If you feel persecuted because your boss says you’re slow, and drivers don’t yield when you step into crosswalks, be grateful you’re not a Wisconsin wood turtle.
Though people and wood turtles can live to 80 years or more, your odds of reaching the milestone are better. These hard-shelled reptiles are a “threatened” species in Wisconsin, and they face endless challenges wherever they look, crawl or nest.
The wood turtle’s foes constantly try to make its life short and miserable. Those threats include poachers and farmers’ plows; hateful drivers in cars and trucks; otters, skunks and raccoons; and plain ol’ invasive plants and woodland succession.
The Department of Natural Resources listed the wood turtle as “endangered” in 1975, but upgraded its status to “threatened” in 1982. The species is generally found north of a line from Wisconsin’s far southwestern corner in Grant County to Green Bay, although it hasn’t been documented in Polk, Pepin, Richland, Waushara, Marquette and Green Lake counties.
The wood turtle’s upper shell measures about 4¾ inches wide and 9½ inches long, and its bottom shell is usually yellow with large black blotches. The upper shell’s individual sections, or “scutes,” grow annual rings that are more obvious than those on other Wisconsin turtles.
If individual wood turtles find a suitable habitat, they’ll live there for years, even decades. Cheryl Todea, executive director at Trees for Tomorrow, an education center in Eagle River, said a female wood turtle nicknamed “Woody” roamed TFT’s property along the chain of lakes for over 20 years. Biologists estimated the turtle was at least 40 to 50 years old when it died a few years ago.
A wood turtle’s struggles often begin when it’s an egg inside its mother. Otters and raccoons know what’s soft and vulnerable on a turtle shell, and some truckers and motorists purposely Goodyear “gravid” wood turtles as they cross roads and highways. (If you don’t know what “gravid” means, just say “pregnant.”)
Either way, the eggs aren’t necessarily safe once female wood turtles lay and bury them in loamy creek bottoms or gravelly roadside right-of-ways. Rebecca Christoffel, co-director of Turtles for Tomorrow (turtlesfortomorrow.org) in Madison, said it’s common for skunks, raccoons or opossums to dig up and eat everything in a wood turtle’s nest, which typically holds nine to 11 eggs. Nest raiders apparently sniff out freshly laid eggs by keying on Geosmin chemicals, those earthy odors produced by soil microorganisms in freshly dug dirt.
“In many areas we’ve checked, recruitment is zero because every nest got raided by predators,” Christoffel said in late July during the Wisconsin Outdoor Communicators Association’s annual conference at Trees for Tomorrow. “It’s not unusual to see no new young enter the population.”
If a nest escapes notice and the eggs hatch, young wood turtles face a long road to sexual maturity. Female wood turtles won’t lay their first eggs until they’re 6 to 7 inches long, which takes 12 to 17 years of good luck and suitable habitat. Even then, some get poached and sold on the black market, and others get “rescued” and adopted as pets.
Despite those challenges, the species persists because its long lifespan often gives females many chances to reproduce. Still, it’s an endless struggle, with each challenge — road mortality, nest predation and natural succession — overlapping the others.
“Wood turtles prefer open, sandy-soiled bottomlands along fast-flowing creeks and rivers with tannin-stained water,” Christoffel said. “Once brush, trees and invasive plants start growing and filling in a bottomlands, wood turtles go elsewhere to nest. The farther they have to search to find good nesting sites, the more vulnerable they become.”
In many cases, the first suitable nesting sites are a farmer’s field or hobbyist’s garden, where nests often get destroyed by plows or rototillers. Other common nest sites are the sandy gravel of road shoulders. Unfortunately, nest-raiders easily find all these exposed sites. And once a raccoon locates a nest, it courses back and forth, systematically searching for others.
Further, the longer a turtle spends on or near a road, the greater its chances of getting clobbered by passing vehicles. Sometimes they’re hit intentionally. A 1996 study in Ontario, Canada, found 2.7% of drivers purposely steered off course to hit turtles or snakes, with male drivers four times more likely than females to target them. Likewise, a 2012 experiment at Clemson University found seven of 267 passing drivers (2.6%) steered to steamroll a rubber replica of a box turtle.
“When turtles nest alongside roads, it’s a double-whammy,” Christoffel said. “Not only do predators easily find the nests and eggs, but lots of mature females get crushed by cars and trucks. When egg-laying females die, it’s hard on the population. Wood turtles evolved to survive heavy predation on eggs and baby turtles, but they cannot withstand heavy losses of adult females. It only takes a few road-kills to hurt wood-turtle populations.”
Mark Naniot, director of Wild Instincts, a wildlife rehabilitation facility in Rhinelander, said his team often works on two or three road-hit turtles daily during their nesting period of late May to early July. He said the most his team can usually do is make external repairs to the shell with epoxy and zip ties, and hope the turtle’s internal injuries heal on their own.
To combat heavy losses of eggs and mature females, Turtles for Tomorrow staff have experimented by clearing large areas of brush and plants in riverbottoms to create nesting areas. Those experiments typically failed when left unprotected, given how systematically raccoons check a clearing after finding one nest.
Success rates increased, however, when staff set up solar-powered electric fences that zap raccoons but allow turtles to crawl under. Turtles for Tomorrow set up 30 of these 16-by-16-foot enclosures across northern Wisconsin, and works with landowners to create similar sites on private lands. These relatively small sites are easier to build, protect and maintain.
Christoffel said Turtles for Tomorrow hopes those efforts will pay off, but it might take decades to document success, given that female woodies need around 15 years to mature.
“We’re doing more quantitative nest surveys to measure how much difference we’re making,” she said.
“Woody,” seen here in 2011, was a female wood turtle that lived over 20 years at the Trees for Tomorrow education facility in Eagle River, Wisconsin. — Patrick Durkin photo