Scientists raising threatened tortoises at a Mississippi National Guard camp to give them a head start in the wild are trying something new: raising a few to sexual maturity and then releasing them.
The Nature Conservancy and the National Guard released their first seven adult-sized gopher tortoises on Sept. 9 at Camp Shelby near Hattiesburg, where the nonprofit has a tortoise hatchery.
Reptile size and sexual maturity are closely related – and the animals were trying to mate and showed other signs of sexual maturity at age 5, project leader Jim Lee, a biologist with The Nature Conservancy, said.
He said five of the tortoises had been raised for six years but had shells about 10 inches (254 millimeters) long, or as big as those which have lived in Mississippi’s wilds for 18 to 25 years.
It’s an intriguing idea, said Tracey Tuberville, a University of Georgia scientist who runs a lab on the Savannah River near Aiken, South Carolina, and hadn’t heard of the latest twist at Camp Shelby.
“Assuming it’s successful, you’re basically providing an incredible boost to the population,” she said Friday. “You're shading off a lot of years” to get adult animals.
Gopher tortoises got their name because they burrow. Their dens become homes to hundreds of other species that live in dwindling longleaf pine forests, including endangered dusky gopher frogs.
Alex Littlejohn, TNC state director, said the release is a “critical step” in fully restoring the Longleaf pine forests throughout Mississippi.
“The role that this iconic species plays in the Longleaf forest cannot be overstated,” he said.
The tortoises are native from South Carolina to Florida and west into Louisiana, but their numbers have fallen as the forests were felled. The U.S. Fish and Wildlife Service – part of the Camp Shelby project along with the U.S. Forest Service and several state agencies – says they are threatened in Mississippi, Louisiana and western Alabama, and a candidate for protection in Georgia, Florida and South Carolina.
Programs in areas with more gopher tortoises or where the reptiles grow faster may not need a longer head start, Tuberville noted. Hers has settled on raising the tortoises for just one year. With a shell length of about 3 inches (76 millimeters), or about the size of a 3- or 4-year-old wild turtle, about 70 percent survive, she said.
“The longer you raise them the more space it takes, the fewer you can raise for the next year’s cohort. And the bigger they are the more mess they make,” she said.
A day before Mississippi’s large tortoises were let go, The Nature Conservancy released 87 kept for that program’s more usual two years, to the size of a wild-grown 6- to 8-year-old.
Those likely have another decade before they can breed, Lee said.
Over the last several years, scientists have released about 400 tortoises with shells 5 to 6 inches (127 to 152 millimeters) long in Camp Shelby.
They were raised from eggs laid by colonies scattered around the 134,000-acre (54,200-hectare) camp in the DeSoto National Forest. To ensure the widest genetic mix, they’re all released at a central location, Lee said.
They’re given 12 hours of “daylight” year-round and as much food as they want, since the amount they can eat and the amount of energy they must spend are the major factors in growth up to average adult size.
Gopher turtles in the wild grow more slowly in Mississippi than in Georgia or Florida, Lee noted. He said that’s partly because the growing season’s shorter and partly because burrowing in Mississippi’s soil, which holds more clay and loam, is more work than in sandy eastern forests.
One concern about the adult-sized tortoises is that longer captivity might keep them from behaving normally in the wild. However, so far, so good, Lee said.
“We only just released them, but I’ve tracked them four times,” going to the release site to check their radio tags and behavior, he said.
“Each one of our animals has either constructed its own burrow or is using a preexisting burrow. That suggests to us that these guys know what they’re doing,” he said.
The seven big beasts include five raised from eggs and kept for six years. The other two were taken from areas dangerous to them and raised to the same size.
“If they all live two or three years, we might be onto something. If they all die within a few weeks this is not a very good idea,” Lee said.
He said he has another eight 3-year-olds that can be released in another two years to continue the experiment, and Camp Shelby’s environmental officer has suggested a building where larger enclosures could be created to expand the program.
“We wouldn’t be able to do that with all the animals we get on an annual basis. But maybe 25 to 50,” he said.
The current building could be considered a middle school where gopher tortoises would stay for two years.
“Then they'd graduate to this bigger facility which had bigger enclosures, like a high school,” he said.