By Ann Deutch Hougham
When my husband and I moved back home to Indiana 16 years ago, we had a young Box Turtle visit our garden regularly. It was a mystery how that little turtle could get in and out of our fencing. We finally caught sight of him or her simply turning sideways and scooting through. Box Turtles are declining in numbers through most of their range so seeing a youngster made us especially cheerful.
In the large contiguous forest near our home, we’ve since seen more than 70 different individual Box Turtles, of which 6 were smaller than a full-grown adult. Clearly, the forest in this part of south central Indiana–not far from Morgan-Monroe State Forest–is vital for the future of Box Turtles because we see that some adults are successfully reproducing here.
Any full-size turtle we see could easily be older than we are; Box Turtles can live to be 100 years old. Box Turtle populations, like so many other wildlife, have diminished over recent years. The Eastern Box Turtle is recognized by the state of Indiana as a species of Special Concern, while several similar and related turtles such as the Ornate Box Turtle, Blanding’s Turtle and Spotted Turtle are listed as State Endangered species. While Box Turtles can forage and nest in a wide variety of habitats, they hibernate in upland forests over winter, burrowing into the soil under leaf litter and woody debris.
Females take about 13 years to reach reproductive maturity. Turtle eggs and hatchlings are so often eaten by predators that it can take decades for a single female to reproduce herself. A few years ago, a Box Turtle laid her eggs near my driveway. It was evening and my husband and I promised each other to erect a protective fence the next morning. To our dismay, a predator beat us to it. We suspected it was a raccoon who dug up her nest and ate the eggs but it could also have been a skunk or a fox.
Increased agriculture, housing and road development can cause a local extinction of Box Turtles that won’t be noticed for many decades because most likely, it’s the eggs, hatchlings and juveniles harmed by these threats. The adults live so long that it’s hard to notice when young turtles aren’t joining their ranks.
Like you, I want my great-great-grandkids to be able to enjoy seeing them just the way we do. A forest healthy enough to sustain Box Turtles will also be home to a diverse community. That forest will support such a variety of animals, plants and microbes with such complex interactions that the old phrase web of life only begins to describe them. And so, what is the impact of logging on Box Turtles?
Researchers on the Indiana Department of Natural Resources Hardwood Ecosystem Experiment (HEE) in Morgan-Monroe and Yellowwood Forests and elsewhere found that logging doesn’t kill turtles within their brief two-year study periods, but it does cause some behavior and physiological changes. For example, after timber harvests the turtles moved more often but shorter distances each day. They often crossed logging roads. Turtles were found more often in the deep forest or on the edge of harvested areas than inside harvested areas.
Can we be sure that logging on a grand scale as now practiced, no matter how careful, will allow Box Turtles to survive over the next century?
Purdue recently published a forest management guide saying, “Based on our current level of knowledge, it is impossible to predict all consequences, positive or negative, of timber harvesting,” (MacNeil). Purdue suggested some Best Management Practices to minimize the problems science already recognizes. Don’t run over turtles, don’t drive in turtle nesting or hibernating areas except when the ground is frozen, leave woody debris on the ground, and don’t disturb temporary spring pond areas. Is this enough to assure turtles will survive in our logged forests? Scientists are not sure.
Here’s what we do know: forest size matters. The bigger the better. Box Turtles in the HEE (Morgan-Monroe and Yellowwood) live in a larger contiguous forest and have larger home ranges than any other studied turtles. Two of the 44 radio-tagged HEE turtles were more nomadic than most. How One of them covered about 464 acres in just one year. One nice warm day, this turtle ended up a football field length away from where it started. Most of the HEE’s radio-tagged turtles stayed much closer to home averaging a home range (home area) of 18 square acres (Currylow 2012 and Saunders 2013).
Turtle nomads are important members of the turtle community. All of the turtles this side of the Appalachians are related as one family according to their DNA (Kimble 2014). How were the family genes spread over such a vast territory? Throughout history some turtles must have been wanderers like the two found in the HEE, traveling far and finding new mating partners all along the way.
A genetic study of Box Turtles all over their range showed that there was historical migration connecting turtles all the way from Missouri to Tennessee. However, the same scientists found evidence that currently, would-be wanderers can’t traverse through the fragmented habitats throughout their range.
Even within their remaining habitat, crossing a road can easily be fatal for a Box Turtle. The same is true on logging roads. Turtles often hide in a little pile of leaves so a person driving a big vehicle on a forest road can’t see them at all. Dividing their range with roads is a source of harm to the population as well as individual turtles. Because the few nomadic turtles cross extra roads, they are more exposed to being run over than stay-at-home turtles. In the past, Box Turtle populations operated at much larger geographic scales. (Kimble 2014)
The Precautionary Principle, or erring on the side of caution when any activity raises plausible or probable threats of harm, guides us to save as many of the few remaining large road-free forest areas as possible. It’s up to us to make sure as many turtle populations as possible have a large area where turtles can roam safely and mate with others who live far away.
The IFA’s proposal to set aside 10% of our State Forests as Wild Areas is a nod to the Precautionary Principle. Creating State Wild Areas would help protect Box Turtles and the community of life in the forest in ways we don’t yet understand.
Currylow AF, MacGowan BJ, Williams RN (2012) Short-Term Forest Management Effects on a Long-Lived Ectotherm. PLoS ONE 7(7): e40473. doi:10.1371/journal.pone.0040473
Currylow, Andrea F., et al. “Seasonal variations in plasma vitellogenin and sex steroids in male and female Eastern Box Turtles, Terrapene carolina carolina.” General and comparative endocrinology 180 (2013): 48-55.
(available on Google Scholar)
Kimble, Steven JA, O. E. Rhodes Jr, and Rod N. Williams. “Unexpectedly low rangewide population genetic structure of the imperiled eastern box turtle Terrapene c. carolina.” PloS one 9.3 (2014): e92274.
Lloyd, Terrell C., et al. “Modeling Hematologic and Biochemical Parameters with Spatiotemporal Analysis for the Free-Ranging Eastern Box Turtle (Terrapene carolina carolina) in Illinois and Tennessee, a Potential Biosentinel.” EcoHealth 13.3 (2016): 467-479.
(not available on the open internet- use a university library)
MacNeil, Jami, Brian J. MacGowan, Andrea Currylow, and Rod N. Williams. “Forest Management for Reptiles and Amphibians.”
Saunders, Michael R.; Swihart, Robert K. 2013. Science in the hardwood ecosystem experiment: accomplishments and the road ahead. In: Swihart, Robert K.; Saunders, Michael R.; Kalb, Rebecca A.; Haulton, G. Scott; Michler, Charles H., eds. 2013. The Hardwood Ecosystem Experiment: a framework for studying responses to forest management. Gen. Tech. Rep. NRS-P-108. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 315-332.