Farm and Field

Environmental DNA detects alligator snapping turtles in southern Illinois

Posted: Mar. 1, 2020 1:10 am

The prehistoric-looking alligator snapping turtle may be the largest freshwater turtle in North America, but that doesn't make it easy to spot.

The up to 200 pound armored beasts have been recorded in Illinois 16 times since the late 1800s, but in a recent study, University of Illinois scientists have demonstrated an effective new method to detect the secretive reptiles in the wild.

"You can't conserve a species or population without knowing where they are. Once we have that foundational information, we can do the nitty-gritty of conservation biology: trying to boost populations through habitat restoration, reintroductions or any number of established conservation tools," said Ethan Kessler, lead author on the study.

Kessler and his collaborators tested how well an emerging environmental sampling technique known as environment DNA, or eDNA, could detect alligator snapping turtles in a southern Illinois river system. The idea is that all organisms shed DNA in the environment, so a simple scoop of soil or water theoretically should contain trace amounts of DNA from all the organisms recently inhabiting or passing through a given area.

The research team knew alligator snapping turtles were in Clear Creek, a southern Illinois stream feeding into the Mississippi River. To prove eDNA is capable of detecting alligator snapping turtles, the research team first identified genetic markers that matched all of the subpopulations across the species range but differed from any other turtle species. After radio-tracking turtles they knew were in Clear Creek, the team took water samples near the turtles as well as in dozens of random sites.

The eDNA method was able to detect alligator snapping turtles up to a kilometer, or two-thirds of a mile, downstream using less than a gallon of water from each sampling location.

"We developed a tool to rapidly go out and look for this species. This could be used in regions that historically have records for the species, but they either haven't been found in many years or have really low population levels," Kessler said.

"But I think just in general, as long as you have a species specific primer, this is a good tool to use for any rare species. And it's a way to maximize our time and effort. A lot of animals need help, and our conservation biologists have limited resources and time to try to get the most good out of the work that we do."

Spring grazing

Seed oats and clovers now to improve spring cattle grazing resources and reduce costs.

"Proper establishment and grazing management of oats and clovers is key for optimum cattle performance," University of Missouri Extension livestock specialist Patrick Davis said.

MU Extension publication G4652, "Seeding Rates, Dates and Depths for Common Missouri Forages," offers helpful guidelines and is available for download at extension2.missouri.edu/g4652.

"Proper grazing management is achieved through strip or rotational grazing," Davis said.

Graze oats about 60 days after planting. For optimum cattle performance, begin grazing oats at 5 to 6 inches. Initial stocking rate can be one animal to three acres. Grazing red clover when about half the plants are blooming will yield a feeding value similar to alfalfa.

White clover is a low dry matter, high digestibility forage that has potential to cause cattle bloat. One way to prevent that is to slowly adapt the cattle to grazing white clover, Davis said. Other preventive measures include providing supplemental proxalene or bloat blocks to cattle. Place white clover in a mixed grass stand to reduce the chance of bloat.

Red clover, a high-quality legume, improves spring grazing resources with less bloat potential.