Tennessee Aquarium's New Study May Help Declining Gopher Tortoises

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Gopher Tortoises are like unseen architects, digging burrows that are home to more than 400 other animals. A new study by the Tennessee Aquarium may help wildlife managers formulate plans to save this keystone species.

• Tennessee Aquarium Conservation Institute biologist Dr. Josh Ennen holds a Gopher Tortoise that resides in the Tennessee Aquarium’s Delta Country gallery.

• Tennessee Aquarium Conservation Institute biologist Dr. Josh Ennen holds a Gopher Tortoise that resides in the Tennessee Aquarium’s Delta Country gallery. (Credit: Casey Phillips)

"By protecting this one turtle species, you’re actually protecting upwards of 400 other species." - Dr. Josh Ennen, Tennessee Aquarium Conservation Institute biologist

With wide, spade-like claws and sturdy hind legs, the Gopher Tortoise seems almost purpose-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 Dr. Josh Ennen of the Tennessee Aquarium Conservation Institute.

“If they were to disappear 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 actually protecting upwards of 400 other species, which is very important.”

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, which appears in the latest issue of the Journal of Fish and Wildlife Management, found that Gopher Tortoises actually 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 so as 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 says. “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. For more information about Gopher Tortoises, go to tnaqua.org/our-animals/reptiles/gopher-tortoise.

Read the full text of the study at: fwspubs.org/doi/full/10.3996/022017-JFWM-010

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Thom Benson
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