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TWS2021: Filling in data gaps for a cryptic but common species
For a relatively common species, researchers don’t know much about the natural history of western spotted skunks in the Pacific Northwest. What landscapes do they prefer? What prey species do they eat?
Researchers are presenting their research tackling some of these questions at The Wildlife Society’s virtual 2021 Annual Conference. “Small carnivores play a crucial role in the ecosystem,” said Oregon State University graduate student Marie Tosa, in the presentation available to conference attendees. “They exert top down pressure on prey species, and merely their presence can influence the ecosystem structure and function. These small carnivores, however, can be very difficult to study and collect data on due to their small size, cryptic coloration and elusive behavior.”
In addition, many small carnivores are facing land use change leading to population declines. While western spotted skunks (Spilogale gracilis) are in the clear for now, Tosa said, the researchers’ findings may shed light on related eastern spotted skunks (Spilogale putorius), which has experienced range-wide declines.
To conduct their research, Tosa and her colleagues collected camera trap data on western spotted skunks from March 2017 to September 2019 amid old-growth forests and logged areas in the H.J. Andrews Experimental Forest, on the western slope of the Cascades in Oregon. Researchers also trapped skunks to fit them with tracking collars and used detection dogs from Rogue Detection Teams to find skunk scat that could tell them what the skunks were eating.
When they collected the camera trap images, more than 60% of the carnivores depicted were western spotted skunks. “This illustrates how abundant the Western spotted skunk is on this landscape,” Tosa said.
The research showed that the skunks prefer old-growth areas at mid-elevation sites. They also found that male skunks had larger home range sizes that females. Using DNA metabarcoding on scat, they determined the skunks’ mostly ate vertebrates, including Pacific treefrogs (Pseudacris regilla) and Humboldt’s flying squirrels (Glaucomys oregonensis). A few scat samples included invertebrate DNA, including land snails, camel crickets, wasps and orb weaver spiders. Scat also included fruit-bearing plants like huckleberry and rooibos. The skunks appeared to consume more plants in the summer and more vertebrates in the fall. They ate insects throughout all seasons.
Their findings were fairly consistent with the literature on eastern spotted skunks, Tosa said. In addition, she said, these findings are important for the larger ecosystem. “These results also show that the western spotted skunk provides a linkage between aquatic, avian and terrestrial ecosystems,” she said.
Conference attendees can visit office hours for this contributed paper on Tuesday, Nov. 2 from 4 p.m. to 5 p.m. to learn more and ask questions.