Scientists might be closer to solving one of the many curious mysteries of the gopher tortoise.
The shy, secretive reptiles have vanished in many areas because of habitat loss, and efforts to relocate colonies threatened by development are often stymied by their innate homing instinct.
“They tend to want to find their way back to where they came from,” said John Jensen, a senior biologist at Georgia’s Wildlife Resources Division.
As part of a project to restore the tortoise to its original range within the state-owned Yuchi Wildlife Management Area in Burke County, researchers are exploring ways to keep relocated colonies from leaving their new habitat.
Tortoises transplanted at the 8,000-acre Yuchi site were confined in specially designed enclosures for nine months or more, Jensen said, after which they tended to stay in the area on being released.
“We were looking for the length of time needed for them to have site fidelity,” he said. “We first released 16 of them and followed 10 with radio-telemetry.”
To help compare behavior among relocated tortoises with those already living at the site, scientists placed transmitters on eight native tortoises.
After a year of monitoring, the nine-month confinement appears to have helped.
“It turns out the relocated tortoises moved quite a bit more, not distance-wise, but just more movement,” Jenson said. “But all of them stayed in the area.”
The farthest any of them wandered was 1.1 kilometers, but even that one ended up going back to its release site and building a burrow near its original pen.
In a similar study conducted in Telfair County by the Orianne Society, a conservation group, all relocated tortoises confined for nine months stayed in their new homes.
“Their tortoises did basically the same as ours,” he said. “So we’d think of this study as a success.”
Since the first release at Yuchi, additional tortoises have been placed on nearby land owned by Georgia Power Co. near the Plant Vogtle nuclear power site.
A hole in one of the specially designed enclosures allowed two tortoises to escape, several days apart, and both of them wandered up to the same security guardhouse near the plant. That’s where they were apprehended by officers who noticed numbers painted on their backs.
When scientists traced a straight line from the breached enclosure to the south Georgia site from which they were relocated, the path went directly past that guardhouse, Jensen said, indicating they were likely trying to return to their home territory.
In all, 57 tortoises have been relocated to the Yuchi site and surrounding Georgia Power preserve, adding to an estimated 44 already living in the area, Jensen said.
More tortoises will be needed before the area can be considered repopulated, though.
“The magic number, for conservation planning, needs to be 250 adults to be self-sustaining,” he said. “So we have a long way to go.”
Gopher tortoises are the official Georgia state reptile – and the continent’s largest land turtle.
They are listed as a threatened species in Georgia and are a candidate for listing on the federal endangered or threatened species list.