Marie Tosa, a researcher at Oregon State University, has spent the past two-and-a-half years roaming the forested mountains of North America's Cascade Range. Why? To study the movements of one of the region's most elusive animals: the western spotted skunk.
The small carnivore is one of a number of species facing significant threats from human-driven land-use changes, says Tosa, who hopes her findings, published in the journal Ecosphere, will help guide future monitoring efforts and highlight potential dangers to the species.
Weighing just 1–2 pounds, the western spotted skunk is notably smaller than its more familiar urban cousin, the striped skunk. “The easiest way to describe them is a tube sock,” says Tosa. “They are mostly black but they have white spots all over them. They have this giant white spot on their forehead. And they’re really, really adorable.”
The western spotted skunk prefers remote, undisturbed habitat, such as the mountains of the Cascade Range, spanning from New Mexico to British Columbia and California to Colorado. It's also nocturnal, so hardly ever seen, explains Taal Levi, an associate professor at Oregon State’s College of Agricultural Sciences and advisor to Tosa.
"For such an abundant carnivore in these forests, we don’t really know anything about them."
Why are scientists studying the western spotted skunk?
Tosa’s research was partly inspired by the dramatic decline of the eastern spotted skunk, which experienced a population collapse of 99% between 1940 and 1980.
“Habitat loss is believed to be a factor in the population decline," says Damon Lesmeister of the U.S. Forest Service, who conducted research on the eastern spotted skunk in the 2000s, "but the reasons are not well understood because the species was not well studied prior to or during the decline.”
The eastern spotted skunk is now listed as vulnerable by the International Union for Conservation of Nature and was considered for listing under the Endangered Species Act.
Researchers are worried the western spotted skunk could face similar risks if not closely monitored.
Levi says that “this project was trying to figure out more about them: trying to learn about their natural history; what they do in these forests; what do they need; how do they influence the ecosystem that they are in.”
Into the forest
The work was conducted from 2017 to 2019 in the H.J. Andrews Experimental Forest, a 16,000-acre research forest of steep hills and deep valleys just east of Eugene in Oregon.
For the first phase of the project, Tosa set up trail cameras, baited with sardines and cat food to lure the skunks. Using images taken by the cameras, she was able to figure out where best to position box traps, which she also baited and camouflaged with moss and bark.
Tosa then spent hundreds of days driving to and from the 100 cameras and 50-100 traps, placing a radio collar on the skunks she found. Once collared, she was able to track the skunks’ movement.
What was found
Tosa’s data revealed that western spotted skunks have a surprisingly large home range of up to 12 square miles – far more than similar-sized mammals, or even deer. She attributes this to their need to roam widely in search of scarce food resources.
Among other discoveries, the skunks showed a preference for both old-growth and younger forests, with the latter offering more food options, such as berries and small mammals. They also proved vulnerable to harsh winter conditions, particularly deep snow, as observed during a 2019 snowstorm. Unlike many other species, the skunks didn’t exhibit territorial behaviour, with home ranges overlapping across 63% of the study area.
The researchers say the observations gained from the study have strengthened their understanding of the ecology and natural history of the western spotted skunk. This in turn can help inform conservation and management decisions to help ensure the survival of the secretive mammal.
Find our more about the study Western spotted skunk spatial ecology in the temperate rainforests of the Pacific Northwest
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