Researchers use eDNA to track lynx, wolverines, etc.

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Round footprints of an unknown animal lead down a snowy road in the Lolo National Forest in western Montana. Jessie Golding bent down to inspect the tracks, then walked slowly along the trail, leaving behind Bigfoot-sized snowshoe prints. It was an abnormally hot day for early February; the sun had gone down on the animal’s tracks until only circular footprints remained. Golding guessed their origin: the Canada lynx. She dropped her bag, put on a fresh pair of disposable gloves, and began scooping snow from the trails into a clean plastic bag. In the snow was an invisible breadcrumb that Golding would later use to discover the animal’s identity: environmental DNA.

Golding is the head of the multispecies mesocarnivore surveillance program for the National Genomics Center and the U.S. Forest Service Northern Region. Over the past five years, she has developed this new method of using environmental DNA, or eDNA, found in snow tracks to identify rare forest carnivore species, including Canada lynx, wolverines, fishers, martens and mountain red foxes. These species live in the forests of western Montana and northern Idaho, but are generally elusive.

The secretive nature of these animals makes it difficult for researchers to monitor the status of their populations. But Golding and his colleagues can use eDNA from tracks in the snow to identify the presence of these species to better understand where they exist. “The first step in being able to conserve a species is knowing where it is,” says Golding. “And you’d be surprised how many times we don’t know.”

eDNA comes from the paws of an individual animal and can be in the form of skin cells or scent gland secretions. When the animal walks in the snow, it leaves behind this genetic material. While looking for food, a lynx can make more than eight kilometers of tracks in a day; a wolverine can sleep even more. The constant movement of these animals in winter means that tracks are ubiquitous in these snowy landscapes.

The process of tracking rare carnivores traditionally relies on visually identifying tracks in the field and following the tracks to a location where the animal has killed prey, fed, or left droppings. Kill sites and feces also contain DNA which is used to identify carnivore species. Another common method is to set up “bait stations”, which lure animals with already dead prey. Small wire-bristled brushes will be set up near the bait to snag the animal’s hair as another means of obtaining DNA samples. But these monitoring methods can be laborious and time-consuming.

However, collecting eDNA samples is quick and easy, says Golding. The main concern is to ensure that each sample is taken without any contamination. This is accomplished with fresh gloves, new bags and sterilized equipment for each sample. Once she has a bag of snow picked up from a track, the sample is kept frozen until it is ready to be taken to the lab. A positive detection of a species can be determined from tracks that are several weeks old and a single strand of DNA is sufficient.

Identifying rare carnivores from eDNA in their tracks initially seemed like a long shot for Golding. She first applied the method in the Beaverhead-Deerlodge National Forest, where the Canada lynx was not known to be found. But in 2018, a private citizen took a photo with a remote sensing camera, and the photo looked oddly like a lynx. The ambiguous image inspired the first test to see if the eDNA method could help confirm what the camera could not.

Not knowing how much snow would be needed to find the eDNA, Golding remembers collecting several gallons of it from the camera trap location and carrying it from the forest. To Golding’s surprise, somewhere in those gallons of snow was the eDNA of a lynx. It changed the situation.

The Canada lynx is listed as endangered under the Endangered Species Act. This means that wherever they are, land managers are required to consider the impact of their decisions on the species, says Scott Jackson, manager of the US Forest Service’s national carnivore program. In order to be able to hunt, reproduce and survive, the lynx needs diverse forests with stands of young and old trees. But good lynx habitat can easily be ruined by uninformed forest management decisions, such as where to log or conduct prescribed burns. “The more we know about the species that may live in this terrain, the more informed our management decisions will be,” Jackson says.

Despite the importance of these fundamental data, they are often lacking for these species in their Rocky Mountain ranges. But as climate change continues to alter the habitat on which these rare species depend, it will be imperative to know as much as possible about their whereabouts and the health status of their populations.

Environmental DNA can make collecting this information more efficient, says Betsy Herrmann, planning and resource manager for the Beaverhead-Deerlodge National Forest. Because collecting snow traces is so simple, Herrmann involved people from his department other than researchers to help with the effort. Now, when US Forest Service law enforcement officers and recreation specialists discover supposed tracks of rare carnivores, they are trained to collect them. More people involved in the monitoring process means covering more ground, Herrmann says.

Golding would like to see this method of wildlife monitoring expanded into a citizen science effort one day. Visually identifying tracks in the snow can be difficult, if not impossible, says Golding. But eDNA is a powerful tool for identifying where the mountains’ most mysterious species have wandered. “I always tell my team, ‘If you’re in any doubt, just clear the snow,'” Golding says.

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