Investigating castaway gopher tortoises of Cumberland Island
What’s learned there could help mainland tortoises threatened by development, says JU professor
They’re castaways, isolated for decades on an island off the Georgia coast. Their ancestors were probably captured and taken there to be lunch and dinner for the earlier, more powerful residents of the island.
But life is pretty good for them these days. Now left pretty much undisturbed on Cumberland Island National Seashore, they’re free to go about their usual business of being gopher tortoises.
“That’s what they say in life, right? It’s all about timing,” said John Enz, an associate professor of biology at Jacksonville University.
He was part of a group that spent much of June on Cumberland Island, covering its entire length to learn more about the gopher tortoises there, an estimated 150 to 175 of them.
The creatures cannot swim, so they most likely didn’t get there by themselves.
Enz strongly suspects they were brought over as food for islanders, back when gopher tortoise was a popular menu item in the Southeast, the only place on Earth where they live.
Once that taste fell out of favor — the stocky, land-dwelling, vegetarian reptiles are now a protected species — the animals were left to their own devices on the mostly wild island.
That made them an ideal study subject, he said: “It’s really exciting, in 2015, to find a group of anything that hasn’t been studied. It’s rare.”
That work caught the attention of a national TV show on national parks, ABC’s “Rock the Park,” which featured the researchers on a program in October. Enz said he and his colleagues were nervous, but relaxed once the show’s hosts began poking around in gopher tortoise burrows with them.
Enz hopes to go back every year to follow the Cumberland tortoises. The research could have implications for those in more developed areas, where they face being relocated when roads and houses and businesses take over the pine savannahs they favor.
Relocations now have a “moderate” rate of success, Enz said. What scientists find on Cumberland Island could help better figure how much room the tortoises need when they are moved.
That matters to more than the tortoises: They’re called a keystone species because the burrows they dig provide shelter for more than 300 other species that depend on them.
Enz and JU sophomore Alexandria Gagne, a marine-science major from Michigan, were joined on the island by a professor and student from Maryville College in Tennessee. JU graduate student Danielle D’Amato was on the island, too, studying its small population of diamondback terrapins, which were also food for earlier residents.
Searchers found 400 gopher tortoise burrows on the island, half of which looked active. The tortoises generally keep to themselves, one to a burrow.
The team covered just about every bit of the island, all 18 or so miles of it. Nothing could be overlooked.
That meant crashing through thick brush rather than going through it. It meant crushing summertime heat, mosquitoes, spiny cactus.
The students did most of the grunt work, Enz readily acknowledged.
Gagne laughed. “When you’re talking walking through the woods, if there’s big brush, you have to walk through it, you can’t walk around it for convenience. That’s the method,” she said. “You’re getting cut up, scraped up, twigs in your hair.”
They found tortoises in three main groups, including one near the famous Greyfield Inn. The biggest group was made up of about 75 spread over 100 acres at Stafford Field, used as a landing strip for private planes for wealthy families with homes on the island.
When a burrow was found, the researchers got its location on GPS, mapped it and set up a flag to mark it. They checked the temperatures inside and poked cameras down to see what was living there. Outside some burrows, they placed motion-activated game cameras to document what transpired when they weren’t there.
“It’s amazing, sometimes, what you see happening outside a gopher tortoise burrow after hours,” Enz said, chuckling.
There are fights: between armadillos, and between armadillos and tortoises. There were various animals coming and going at all hours. And right outside the burrow is where gopher tortoises mate, said Enz, who — when asked — can do what one presumes is a good impersonation of a male gopher tortoise bobbing its head to entice a female out of its home.
When the scientists arrived on the island, they had just sketchy, anecdotal information about the tortoises. No one knew how many there were. No one knew what their health was like.
The animals can live 50 to 100 years, and Enz wondered if they were a viable, reproducing population, or just a remnant group doomed to dying off one by one.
The research team quickly found nests with eggs, along with juveniles tortoises and healthy adults. Left alone, Enz said, the castaway gopher tortoises of Cumberland Island are doing just fine.
Matt Soergel: (904) 359-4082