SUNY-ESF research collects saliva as source of bear DNA

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Handling and collecting DNA from large animals, such as bears, can be labor-intensive and expensive, but SUNY-ESF’s Rachel Wheat found an alternative source: saliva from leftover salmon carcasses.

Wheat is currently a postdoctoral research fellow at the State University of New York College of Environmental Science and Forestry but did the study for her doctoral dissertation at the University of California, Santa Cruz.

Wheat said she, along with other scientists, were curious about “environmental DNA,” which are other sources of DNA that can be in the environment instead of physically handling the animal.

“We can use the information stored in DNA for a variety of purposes — identifying individuals, tracking animal movement, building family trees to look at relatedness,” Wheat said in an email, “but good-quality DNA can be difficult to collect, especially when studying large, wide-ranging animals.”

Blood and tissue are the best sources of high-quality DNA, but it’s difficult and costly to capture large animals to obtain these samples, and capture is also hard on the animal itself, she said.

While working in southeastern Alaska, which has a high population of brown bears, Wheat came across half-eaten salmon carcasses every day. Her friend and co-author of the study, Sophie Miller, came to visit and while watching the bears feed on salmon, Miller had the idea to swab the salmon carcasses for saliva, Wheat said.

During the summer and fall of 2014, Wheat collected enough data to bring to Oregon State University, where she worked in the lab of other co-author Taal Levi to extract and analyze the DNA to identify individual bears, Wheat said.

The study was funded by her National Science Foundation Graduate Research Fellowship and grants from the National Geographic Society, the International Bear Association and the Alaska Chilkoot Bear Foundation.

There are other forms of environmental DNA, such as a bear’s hair or scat, but saliva lasts longer and is easier to find, Wheat said.

“Coastal areas in British Columbia and Alaska often do not have road access, so logistically, brown bear studies in these regions can be prohibitively expensive,” Wheat said. “… Saliva, as an alternative, should help researchers in these regions because spawning areas can be access relatively easily via boat.”

She also said using saliva is more feasible because researchers can get large samples in one place since multiple bears can feed at the same salmon spawning site. This way, researchers can sample a large proportion of the population at once instead of having to search for single scat or hair samples, she said.

“We also feel that saliva sampling in general is underutilized in ecological fields,” Wheat said. “Saliva provides relatively good-quality DNA, and although most animals don’t leave piles and piles of half-eaten food remains around, saliva sampling should be generalizable to other wildlife species.”

Wheat’s latest research focuses on moose in the Adirondack Mountains. She is working with associate professor at SUNY-ESF and associate director of the Roosevelt Wildlife Station Jacqueline Frair to find how the recently recolonized population is trending and if there are any factors limiting its growth.


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