Surveying species through environmental DNA

MANGDE CHHU RIVER :: BHUTAN

Tigers are big eaters. Ensuring they have sufficient food is key to recovering and maintaining their numbers in the wild. To locate and assess prey and predator populations, scientists have traditionally relied on costly and time-consuming camera trap surveys. But WWF surveying expert Arnaud Lyet thinks there might be a better way: eDNA.

Environmental DNA, or eDNA, is the genetic material that animals leave behind in water, soil, and even air when, for example, they shed fur or skin. By extracting eDNA and matching it to a database of genetic sequences, scientists can determine the presence of a species in a given area, information Lyet says can be “sufficient for making good conservation decisions in many situations” at a fraction of the price.

In 2022, Lyet led a pilot study to inventory wildlife in and around Bhutan’s Royal Manas National Park. After analyzing the eDNA in 48 water samples, his team detected 134 species—including several tigers and their prey, such as muntjac and serow—proving eDNA could effectively complement camera trapping in future national tiger surveys. They also detected the critically endangered white-bellied heron, which has a known local population of just three individuals, demonstrating, says Lyet, that this technology can accurately identify even a species whose numbers are incredibly small.