Home for Wayward Tortoises . . .
At the SCDNR’s Aiken Gopher Tortoise Heritage Preserve, scientists are studying new techniques that could help bring back this threatened species.
On a drive to the Aiken County town of Williston one early morning near the end of February, I was mesmerized by the delicate beauty of pink-tipped, early-blossoming peach trees shrouded in a heavy morning fog along Highway 278, but I failed to take my old friend, SCW magazine photographer Phillip Jones’ sage advice — “when you see a beautiful shot, stop, it may not be there the next time.” He was right, a freeze just a week or so later put a serious dent in those early bloomers.
But I was in a hurry to get where I was going, excited by the prospect of seeing firsthand a unique research project that SCDNR scientists are working on in this part of the world. I was headed to Aiken Gopher Tortoise Heritage Preserve to meet SCDNR herpetologist Will Dillman and a crew of technicians from the Webb Wildlife Center involved in tracking the movements of gopher tortoises released there. But if you look at it right, the open longleaf pines, wiregrass, broom sedge and early-blooming wildflowers at AGTHP, the result of years of careful habitat management, are every bit as pretty as blossoming peach trees. The judicious use of prescribed fire and other management practices on the property are returning large portions of this sixteen-hundred-acre heritage preserve back to the type of habitat that was here prior to European colonization — particularly beautiful if you are one of the many fire-adapted species who evolved over centuries to thrive in this habitat, like, say . . . a gopher tortoise.
Tortoises have been part of the South Carolina landscape for millions of years, and tortoise fossils are well known from South Carolina, Dillman tells me when we meet up at the preserve’s parking lot. “Right now we’re standing on the ‘Edisto Ridge,’ a geographic feature that provides exactly the type of deep sandy upper layer of soil that these tortoises need.”
Gopher tortoises were once so numerous in this part of the world that the Jasper County town of Ridgeland was originally known as “Gopher Hill,” there’s even a gopher tortoise statue in the town square. But today, these critters are threatened across much of their former range —primarily from loss of habitat. When the SCDNR first acquired this property in 1993, there were fewer than a dozen tortoises remaining here, says Dillman. The property is in the northernmost part of the tortoises' known range. SCDNR botanist Bert Pittman is credited with finding the first one. Pittman was conducting a survey of flora on the property. At that time the tortoise-friendly habitat here was extremely fragmented — not much pine savanna left. Pittman stumbled over a tortoise burrow and immediately realized what it was.
“They were surviving on an open sand hill that had not yet closed in with scrub oaks,” said Dillman. “But they were so far apart, they weren’t even interacting with one another.”
In 2006 SCDNR biologists in collaboration with the Savannah River Ecology Lab beganputting those remaining animals together in a low-walled pen as a way of jump-starting the process of creating a colony — gopher tortoises’ normal social structure — which they hoped would, eventually, lead to reproduction. Since then, nearly 300 tortoises have been released on the property, and scientists from multiple agencies are involved in a collaborative partnership here leveraging a unique research opportunity that is like no other in the United States. The idea is to see whether “waif” gopher tortoises collected from other locations around the U.S. can re-bond into new social groups and form new colonies, alongside tortoises that were hatched here. It’s a long-term study, involving scientists from the SCDNR, the U.S. Fish and Wildlife Service, the University of Georgia’s Savannah River Ecology Lab, the Riverbanks Zoo in Columbia and others. So far, 282 tortoises have been released at the site, with careful records being kept of each one.
“We try to go after and use funds from a lot of different places to achieve the best benefit on the ground,” says Dillman. “It’s been a long-term collaboration with SREL and UGA.”
SREL scientists first began putting turtles out on the property in 2006. The tortoises that have been relocated to this spot come from everywhere. From nearly every state, including some states that don’t even have them – Rhode Island, Kansas, even Massachusetts. The animals are fairly common in some parts of Florida and Georgia.
“Somebody goes to Florida on vacation and they end up bringing home a tortoise, and then they realize they can’t really care for it and they shouldn’t have it,” says Dillman. “And then they look for a way to do something with it, and after some Internet research, will end up calling us or calling Florida, trying to do the right thing. We’d much rather those tortoises be returned to the landscape than become somebody’s pet.”
The tortoises aren’t just turned loose willy-nilly. They are first acclimated to their new surroundings in one-hectare (2.5 acre) pens that keep the wayward transplants all in the same location for a while. The idea is to try and force a bunch of tortoises who have not grown up together to form new bonds and a new community. The pens are an important part of the study — scientists are hoping to learn what techniques work best in helping the turtles develop “site fidelity,” and so far the evidence is strong that the pens help. That information will be useful to biologists in other parts of the tortoises’ former ranges who are working to re-establish these animals where the habitat will allow.
“It’s real clear from work we’ve done on the Savannah River Site that if you just turn them loose, they are just going to walk and scatter.” says SREL scientist and UGA professor Kurt Buhlmann, whose been working at the site from the very beginning.
There’s several reasons for that. Gopher tortoises are long-lived and they have a sense of where they belong. If one gets uprooted from its “home,” its first instinct is to strike out to get back to it. But increasingly, scientists also think it has to do with social structure — i.e., “home” is where the colony is — so penning the “waif” tortoises during their transition is a way to encourage translocated animals to adapt their new surroundings and new social group.
“If you put them in a pen, even though they’re all strangers to each another, by the time they’ve lived in a pen for a year and shared burrows and all – they kind of know each other. So in addition to establishing site fidelity, you’ve also established a community structure (though that’s harder to measure),” added Buhlmann.
Beginning with the first pen in 2006, many of these animals have been radio tracked to record their dispersal, or in some cases, settling in, at AGTHP. A few are still living on the site of that original pen, taken down in 2008.
“It’s work that started on the Savanah River Site, and now it’s been done here, and as we are developing these guidelines for the best ways to relocate tortoises, it is becoming the model for how other states do it,” says Dillman.
As part of this project, a three-person team of young wildlife technicians — Jonathan Cooley, Joel Mota and Olivia Thomas under the direction of Dillman have been visiting AGTHP weekly to check the location and status of twenty-four juvenile tortoises hatched at the SREL that were outfitted with radio transmitters before being released from their pens. It’s not their only task — not even close — the three work on a variety of other reptile and amphibian research projects, but it’s an important one. Among other projects, they also spent several months this past winter hiking across miles and miles of Lowcountry terrain conducting “transect surveys” to identify other places where tortoises might be present and in what densities. Much of the land involved is private property managed for hunting. Landowners have been generally happy to help, but the crew had a narrow window between the end of deer season and the beginning of turkey season to get their work done.
I first met these guys at the Webb Wildlife Center, while hanging out with another team working on a wild turkey research project [link to turkey story], and like those researchers, the gopher tortoise team uses some pretty impressive technology to track the movements of the animals they are studying.
The tortoise burrows themselves are pretty darn interesting. As I follow the survey crew around the property, snapping pictures at each spot where they stop to take a reading, crew leader Johnathan Cooley tells me they can be up to 30 feet long and as much as ten feet deep. But in some cases the “burrow” is very shallow — really just a small tortoise-shaped hole in the ground. This is somewhat tied to their age, says Cooley; the more mature the tortoise, the more likely it will have a deeper burrow. The locations where the radio-tagged tortoises the team is tracking are well-mapped, and they move efficiently from one burrow to the next, listening for the telltale beep from the receiver unit that lets them know a particular tortoise is still there — still alive and well.
In herpetologist-speak, it’s called the “weekly survival analysis.” When possible, the team will also try and get a visual sighting on each animal, which can entail looking into the burrow with a long fiber-optic “scope.” All of the tortoises being tracked by the team were released within the past year, but some were “headstarted,” spending a year in a more controlled environment before being put in the pens. This allows the tortoises to be released at a larger size. An important question their data collection will hopefully answer is whether the headstarted tortoises fare better in terms of mortality, post-release.
Constantly checking a spreadsheet for the correct frequency of each animal being tracked, the crew visits the last known location of each tortoise on the list, listening for the beep on the VHF receiver. By adjusting the strength of the receiver and following the signal, it’s even possible to tell exactly where in a deep burrow a tortoise is — closer to the front, or further back. Joel Mota is really good at this.
“So what I’ll do is follow this beep, and lower the power to get a more accurate position on the animal, as to where it is,” he says.
The tone of the beep changes from soft to more staccato as the signal improves, so he can follow and locate the tortoise by walking in the direction of the stronger signal. The change in tone is very subtle, and it’s impressive to me that he can hear and interpret the changing sounds so easily. To my untrained ear, they sound largely the same, but Mota can zero in on a tortoise’s direction within just a few beeps.
“So I’m getting the strongest signal right here,” he says, standing well back from one burrow’s opening, marked with a shiny silver tag. Their notes indicate that this tortoise hasn’t moved since mid-October — hunkered down in its 6-foot-long burrow. A quick check with the scope verifies that the turtle is still in his spot. The animals have been burrowed up for most of the winter, but the same unseasonable warm spell that jump-started those peach blossoms has some of the tortoises beginning to move. Once spring weather really gets going, the crew may have to do their checks more frequently.
At one small burrow marked “#925” where a tagged tortoise was alive and accounted for the previous week, we get no signal. The animal could be on the move—sunning itself or foraging, explains Cooley. If it’s more than about a kilometer away, the signal could be lost. Another possibility is that the transmitter battery may have died. At another burrow marked # 904, the team checks on a large female who hatched a clutch of eggs last May, which are now being headstarted at the SREL. Those tortoises will eventually also be released on AGTHP.
At the next burrow, Joel locates the tortoise a few feet from the hole, using the signal from the antennae to zero in on his exact location. Otherwise it would be pretty difficult to find, even just a few feet away. The tortoises are pretty well camouflaged for their environment. Lupine is sprouting everywhere, along with other green shoots starting to push through the brown grasses covering the ground. Tortoises like to graze on a variety of forbes and grasses. That’s mainly what, apart from the deep sandy layer for burrowing, makes this habitat work for them.
The extensive work being done on this by SCDNR and SREL scientists and technicians is one of the only studies of its type being done right now, so in the herpetology world, a lot of eyes are focused on this unique Aiken County property. It’s just one more way in which the dedicated scientists of the SCDNR’s Wildlife & Freshwater Fisheries Division are working to protect and conserve our state’s amazing natural heritage.