Rare tortoises getting head start at Aiken heritage site
Posted Sunday, January 20, 2019 6:00 amBy David Lucas
S.C. Department of Natural Resources
Research being conducted at South Carolina Department of Natural Resources’ Aiken Gopher Tortoise Heritage Preserve is a true team effort that will help identify best practices for repopulating this imperiled species – hopefully keeping it from reaching « threatened » status here in South Carolina.
The first thing I learned on a recent visit to the preserve to photograph a group of juvenile gopher tortoises being released into a 2.5-acre « pen » is that 2-year-old gopher tortoises reared in captivity are roughly the size of small grapefruits – that is, if the grapefruits were smashed a little flattish (and had cute, charismatic heads and small, scaly feet poking out of them). The 1-year-olds are more tennis-ball-sized (or I guess avocado-sized, to keep the fruits and veggies metaphor going).
That’s somewhat larger than their similar-aged counterparts would be in the wild, and the scientists working to repopulate this species at the preserve are hopeful that the « head start » provided to captive-reared tortoises will make a difference in their chances of long-term survival. Gopher tortoises are listed as a state-endangered species in South Carolina and are also candidates for federal listing under the Endangered Species Act.
Partnerships a key to success
Bringing a viable population of tortoises back to the preserve is a long-term joint project for SCDNR and for the University of Georgia’s Savannah River Ecology Lab, where researchers have been studying these critters at the preserve and other sites within their historic range for more than a decade. More recently, their efforts have been bolstered by partnerships with Columbia’s Riverbanks Zoo and by financial support from the nonprofit The Longleaf Alliance. The hatchlings are the offspring of « waif » tortoises rescued and translocated from other states such as Florida.
The U.S. Fish and Wildlife Service has provided significant funding for activities to restore gopher tortoises at the preserve since the beginning of the project. Funding from the USFWS, Riverbanks Zoo and the Animal Welfare Institute has allowed partners to begin to evaluate the success of restoration efforts, and a recent grant award from the National Fish and Wildlife Foundation to The Longleaf Alliance, made through its Forestland Stewards partnership with International Paper, will help to increase the lab’s capacity to provide even more head-started tortoises for release into the wild. American Forests also recently provided some funding to support this project. This growing group of agencies is working together to conserve this imperiled species in South Carolina.
Gopher tortoises require a very particular type of habitat (fire-adapted longleaf pine sandhills), and the disappearance of much of that landscape in the southeastern portion of the Palmetto State because of development, timbering and agriculture is why, by the late 20th century, these once fairly common critters had begun to disappear from the landscape.
So, step one in rebuilding a sustainable gopher tortoise population is restoring the appropriate habitat. That’s exactly what SCDNR has been engaged in over the last decade at the preserve, gradually bringing back the landscape on 1,400-odd acres to a long-leaf pine and wiregrass-dominated ecosystem using prescribed burning and other strategies.
Outside the confines of rearing facilities like the ones at the lab and Riverbanks – where the routine includes optimal nutrition delivered daily and zero predators – life for small tortoise hatchlings is fraught with peril, says lab Senior Research Associate Kurt Buhlmann.
« These things are snacks for everything, » he explains. « Maybe you’re lucky if two out of 10 survive the first year, and remember, these guys have to survive for 15-20 years to produce their first clutch of eggs if they’re a female. »
Those are pretty daunting odds, but upon reaching sexual maturity, a female tortoise may produce up to 400 eggs (as many as 10 per year) over her lifespan. So, if just two or three of those 400 hatchlings make it to maturity, that’s enough to keep a population stable. With the headstarted tortoises, survival rates after that first year are more like 75 percent, Buhlmann said. And by closely monitoring the tortoises released on the preserve, scientists hope to refine post-release strategies and protocols that will increase those odds even more over time.
Today’s group of head-started tortoises are released into a 2.5-acre « pen » (just a low wall made of thin sheet metal, but it’s enough to keep them from wandering very far) on a portion of the preserve with great habitat that is pockmarked with tortoise burrows. This technique, developed by the lab’s researchers, has proven to be effective for developing « site fidelity. » Eventually, the walls will come down, but the hope is that by that time the tortoises will have adapted to their new habitat and developed social groups with other nearby tortoises that will last throughout their lifespans.
Needless to say, there’s a lot more to this project than just releasing the tortoises and waiting to see what happens. Each released tortoise – whether within the confines of the pen or outside it – is marked with a unique identifier, and the GPS coordinates where each is released are carefully recorded. These initial data points will form the baseline record for what will be years of intensive monitoring and data collection.
Some of the tortoises are equipped with radio tracking devices that allow technicians to find them using radio telemetry and download detailed data about their movements. Data is collected on a weekly basis during the warmer months, when they are most active, and every two weeks when they are hunkered down for the winter, said SCDNR Herpetologist Andrew Grosse, who recently inherited the project from former project coordinator Will Dillman, now SCDNR’s assistant chief of wildlife.
« We’re really interested in where they are moving and how far are they moving, » Grosse said, « and more specifically, what habitats they are using and how well are they able to survive. »
The eventual goal for Aiken Gopher Tortoise Heritage Preserve is at least 250 animals released, the number that scientists working on the project feel will make for a viable, self-sustaining population on the property, but what they learn about these new techniques will have a much wider application and could change how these types of re-population projects are approached in the future.