Nashville Biologists Track Eastern Box Turtles
How these chelonians live and interact in urban settings.
The Tennessee Wildlife Resources Agency (TWRA) and the Nashville Zoo at Grassmere are tracking eastern box turtles (Terrapene carolina carolina) in Nashville to determine how their urban environment affects them. Dr. Brian Flock, TWRA’s Wildlife Diversity and Intern Coordinator, created this tracking project with two goals in mind. “The initial idea was to have something to help students in the Nashville area learn about wildlife conservation in their backyard while gaining important information on urban box turtles,” Flock told REPTILES. The lack of information on these animals was the main reason that Tennessee’s Comprehensive Wildlife Conservation Strategy listed them as a species of Greatest Conservation Need in 2005, and they have remained on this list ever since.
Tracking of Terrapene carolina carolina Begins
After deciding to launch this project in TWRA’s own backyard, Dr. Flock asked TWRA Wildlife Diversity Aquatic Biologist Anna Dellapenta to conduct the fieldwork. In September 2019, Dellapenta began tracking the population of box turtles at TWRA’s headquarters in Nashville.
Another dense population of box turtles thrives at the Nashville Zoo, less than five miles from the TWRA’s headquarters. For years, zoo staff have maintained a photo collection of the box turtles they find on zoo property. When James Flaherty, herpetology keeper II, arrived at the zoo two years ago, he was surprised to find so many box turtles on the grounds. Flaherty has always been interested in local wildlife projects and quickly became fascinated with these animals. Flaherty analyzed the unique patterns on the turtles’ shells as depicted in the photo collection, which enabled him to estimate that 20 individual turtles are included in the photographs.
After Flaherty and his boss began developing plans to investigate the zoo’s turtles, his boss happened to mention their plans to Dr. Flock. Dr. Flock provided Flaherty with the equipment, and launching in October 2020, the Nashville Zoo is now the secondary site for the project.
Using Radio Telemetry to Track the Turtles
Dellapenta and Flaherty use radio telemetry to track their turtles. When they locate a turtle, they glue a transmitter to its shell. When they want to check on a turtle, they carry a receiver and an antenna to pick up the signal from that transmitter. The equipment guides them to the turtle’s exact location.
They also rely on scute notching to collect data about these turtles. Scutes are the external bony plate on turtle shells, and Dellapenta and Flaherty use a file to mark a notch of a few millimeters wide in the scutes according to a code. Each scute represents a different letter so they can glance at a turtle’s notches to read the code identifying that turtle. While scute notching does not allow Dellapenta and Flaherty to track turtles to their location, it allows them to include every turtle in the study even if they don’t have the means to track them all.
In addition to marking, Dellapenta and Flaherty gather some initial data when they find a new turtle. They measure the length, width, and height of the shell and weigh the turtle. They estimate the age of the turtle based on scute growth marks and record whether they believe it’s a male or female before releasing it.
After more than a year of fieldwork, Dellapenta is tracking 25 turtles with radio telemetry equipment and has notched 10 to 15 more turtles. Even though Flaherty began just a few weeks before the turtles became inactive in winter, he is tracking seven turtles. The zoo staff have pitched in to help Flaherty locate these turtles, and all but one were located by other staff members working on the property.
Telemetry and GPS
Every week when the turtles are active, Dellapenta and Flaherty locate the turtles using their telemetry equipment and record the GPS coordinates of their locations. They note if they are engaging in an activity such as mating, and they weigh them. Weight data for females is especially important to learn about their breeding habits and whether they have recently laid eggs.
During the winter, the turtles go underground until spring.
“They dig deep and sort of horizontally a little bit so you can’t see a hole at all. If you were just walking in the woods, you’d have no idea that there could be a box turtle. . . Six to 10 inches under your foot in the winter,” Dellapenta says.
Dellapenta and Flaherty don’t weigh or disturb them during this period as this could be harmful to the turtles. Instead, they use their telemetry equipment to locate them and ensure they haven’t moved.
Because they want to have several years of data, the team has not yet made any conclusions. However, the data they are collecting does have immediate uses. This data will allow them to determine how many turtles exist on each property. For Flaherty, he is particularly interested in accomplishing this because “[a] crucial aspect of being good stewards of our turtle population is knowing the basics of how many there are and how many males and females and various measurements of population.” Flaherty anticipates that they will be surprised at the total number and estimates that the zoo could have as many as 40 or 50.
They can also discover the home ranges of these turtles, how far they travel in a week, and which resources they utilize. By identifying the areas where the turtles spend the winters, forage, find water, and lay eggs, the TWRA and the zoo will be better able to protect the turtles. “We could analyze those areas and try to figure out exactly what about them the box turtles are either attracted to or they need or thriving off of—whatever it is about that area,” Dellapenta says. “We kind of need to know because that may in the future sort of dictate how we manage the species in the state.”
Box Turtle Behaviors in the Blackberry Patch
Dellapenta has already witnessed some of her turtles reacting to changing resources. This behavior reminds her of other box turtle accounts and research indicating they may remember where and when resources are available in their environment. “When blackberries got into season this summer, three of my female turtles just bolted for the blackberry patch,” Dellapenta says. “And it’s hard to say exactly what they’re doing in there whether they are just chowing down or whether they’re like well, ‘I’m going to lay my eggs under all of these thick thorns and brambles so that nothing gets to the nest.’” For her, this close observation is an opportunity to learn the reasons for their behavior as well.
These scientists hope to continue this tracking project as long as they have the funding and staff to do so; they have several ideas to develop the project in the future. For example, they may expand the project to a non-urban site so they can compare data from urban turtles to those who live in a different environment. They may investigate how temperature affects the turtles throughout the year and may monitor them for potential diseases. They have discussed studying how exotic plants such as privet or honeysuckle influence turtles’ movement and use of their habitat, and they may expand to studying whether the turtles are suffering genetically by being confined to their population. There are many possibilities, but as Flaherty says, “We’re taking it sort of a turtle at a time right now.”
Maggie Gigandet is a Nashville-based freelance writer. You can reach her at www.maggiegigandet.com.