With wide, spade-like claws and sturdy hind legs, the gopher tortoise seems almost built to move earth. Like shelled bulldozers, these reptilian excavators dig deep, winding tunnels beneath the scrublands and coastal dunes of the American Southeast. These burrows provide crucial shelter for the tortoises as well as hundreds of other species, from Eastern Indigo snakes to gopher frogs to burrowing owls.
Despite the positive ripple effect gopher tortoises have within their ecosystems, their numbers in the last century have fallen by 80 percent – including those living on federal land – due to habitat loss and fragmentation caused by human activity.
For a keystone species like the gopher tortoise, a continuing decline would be a big problem for a lot of other animals, explains conservation biologist Josh Ennen of the Tennessee Aquarium Conservation Institute.
“If they and their burrows were to disappear, it would affect numerous species. The importance of gopher tortoises is disproportionate to their abundance,” Ennen explains. “By protecting this one turtle species, you’re protecting upwards of 400 other species.”
The genetically distinct population of gopher tortoises found west of the Tombigbee and Mobile rivers was federally listed as threatened in 1987.
Despite facing a multitude of imperilments, however, tortoises living east of these rivers lack federal protection.
Maintaining a species’ genetic diversity is crucial to ensuring its long-term survival. Until recently, however, scientists lacked a comprehensive examination of gopher tortoise genetics with which to ensure the species’ gene pool remained healthy and robust.
In a recently published study, Ennen and Tennessee Aquarium Conservation Institute geographic information systems analyst Sarah Sweat joined other Southeastern researchers in producing a genetic survey of gopher tortoises across the species’ entire range. In all, the group sampled more than 930 gopher tortoises from 47 sites in both the species’ listed and unlisted regions.
The study found that gopher tortoises comprise five distinct genetic groups rather than two, as was previously supposed. Researchers found that rivers such as the Mobile and Tombigbee, represent an important barrier to genetic intermingling of these groups.
The findings pave the way to individually manage these sub-populations of gopher tortoises to preserve the species’ genetic diversity. Doing so would represent an important step in formulating a long-term conservation plan, Ennen says.
“If you have separate populations that are different, genetically, you want to maintain that evolutionary potential,” he adds. “It’s a great conservation value because when you protect this one species, you protect a whole ecosystem.”
Guests to the Tennessee Aquarium can observe the way other animals use gopher tortoise burrows by visiting the Delta Country gallery inside the River Journey building.
Source: Tennessee Aquarium