It’s no secret that Florida has a snake problem. The Burmese python, which can reach up to 200 pounds and stretch to more than 20 feet, first became common in the Everglades in the late 1990s, likely as escaped pets. The snake quickly settled into its new home, breeding and taking down rabbits, bobcats, and other native animals in its path.


Wildlife managers in Florida turned to expert snake hunters, electronic tracking devices, and search dogs to wrangle the pet-turned-ecosystem-wrecker and had little success. The snakes, although massive, are hard to find in the south Florida habitat. “They’re well camouflaged, secretive, and often slow moving,” says geneticist Margaret Hunter of the US Geological Survey, Wetland and Aquatic Research Center.


Biologists thought the Arthur R. Marshall Loxahatchee National Wildlife Refuge was one place that was safe. Pythons have on rare occasion been spotted there, but only in areas easily accessible to humans, suggesting that the snakes were likely released pets rather than a growing population. But from 2014 through 2016, Hunter combed the waters in and around the refuge for environmental DNA (eDNA)—the trail of DNA left behind by an organism in sources such as feces, mucus, gametes, and shed skin or hair. The results suggested that the python’s DNA was, in fact, widespread throughout the refuge.


Hunter is one of a growing group of researchers who are using eDNA to track invasive species that they’d like to remove and vulnerable species they’d like to protect. Hunter also developed an eDNA test for manatees that’s more sensitive than traditional aerial surveys.


But challenges remain before eDNA can become a widely used tool for conservation biology. The technique carries the risk of false negatives and false positives. And it’s not always clear how to make eDNA results translate into putting eyes, and hands, on the actual animals that managers are after.


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