Carl Zimmer
MATTER
You wouldn’t think hellbenders would be hard to find: The gargantuan salamanders, the biggest amphibians in North America, can grow up to 30 inches long. Yet hellbenders make themselves scarce, living on the bottoms of mountain streams, lurking under massive rocks.
As a result, locating hellbenders takes a crew of scientists. First, some of them must wedge a long pole under a rock to hoist it up, and then their colleagues must plunge into the chilly water to catch their quarry.
A couple of years ago, Stephen Spear, a conservation scientist at the Orianne Society in Athens, Ga., heard about a possible alternative. Instead of searching out rare animals, some experts were gathering animal DNA from their habitats. That way, they didn’t have to track down a species to be sure that it was there.
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Environmental DNA can help scientists track unwanted animals, too. Detecting invasive species is crucial for efforts to control them, but conventional methods aren’t always adequate. Antoinette J. Piaggio of the National Wildlife Research Center and her colleagues have found that Burmese pythons in Florida wetlands are leaving behind detectable DNA, which may be helpful in following their alarming spread.
Environmental DNA can provide some important clues about species in decline, as well. It is hard for scientists to decide when to declare a species officially extinct, since a few stragglers may still survive unseen. But even these hard-to-find animals will still shed DNA into their environment, a signal to scientists that the species survives, if barely.
Researchers still need to learn more about how DNA survives in the environment before these new methods can stand on their own, said Dr. Willerslev. But he was optimistic that environmental DNA would begin providing more clues to zoologists about the animals they study, such as population sizes and the diversity of species in a particular ecosystem.
Those hopes might seem farfetched. Then again, so did the notion that genetic traces of a deer might linger for weeks in the pond from which it drank.
