In Wyoming, a feisty five-pound canid known as the swift fox is expanding into new territory.
A native of the Great Plains, the swift fox can be found in shortgrass prairie habitats from Texas to Canada. In Wyoming, this prairie-dog-consuming critter typically wasn’t found west of Shirley Basin—until recently. Swift fox populations have now been observed in shrubland habitats as far west as Riverton.
Currently, it’s unclear why swift foxes are moving into less favorable habitats, or how this shift might affect their diet and behavior. A group of researchers in the UW Department of Zoology and Physiology, including graduate student Kelsie Buxbaum, aims to learn more.
Breaking convention
As small canids, swift fox prefer landscapes where they can spot predators from a distance and quickly dive into the safety of a burrow. With relatively flat topography and plentiful food sources, shortgrass prairie provides an ideal habitat. But in locations like Riverton, swift fox populations have settled in areas with tall sagebrush and significant variation in topography, both of which reduce visibility.
To find out how this habitat change affects swift fox populations, Buxbaum is comparing habitat use and diet in three different study areas: Laramie, the Shirley Basin, and Riverton. The Laramie site is classified as conventional habitat, while the Shirley Basin site is a mosaic of shortgrass prairie and shrubland. The Riverton site represents a completely unconventional habitat consisting mostly of tall sagebrush.
“We’re looking at how swift fox utilize landscape features similarly or differently in each habitat type—which features they potentially select or avoid,” Buxbaum explains. Her group uses GPS collars to track swift fox movement and then uses remote sensing data to pair locations with vegetation types.
Diet analysis
Buxbaum also seeks to better understand how habitat changes affect the swift fox’s diet. In both the Laramie and Shirley Basin study sites, researchers have observed sizable prairie dog colonies, an important food source for swift fox. In contrast, the Riverton site appears absent of prairie dog activity.
Starting in August 2021, Buxbaum’s group collected 250 scat samples, which are currently undergoing DNA analysis at the U.S. Forest Service National Genomics Center. This analysis will indicate what types of food—insects, plant matter, or different types of mammals—swift fox consume in different habitats and seasons.
Buxbaum predicts that in unconventional habitat types, swift fox are likely consuming other rodents, such as kangaroo rats and wood rats, as well as members of the rabbit family.
Counting kits
In spring 2022, Buxbaum began tracking kit populations at each study site, using GPS collars and VHF (very high frequency) technology to locate individual dens. She installed game cameras at each den to monitor the number of kits observed and when those kits came aboveground. The latter will allow researchers to estimate when the kits were born.
“The reproductive aspect is an important metric that will be used by Bureau of Land Management1 biologists to help reduce impacts on swift fox,” says Buxbaum. “It’s also a metric that can be used to assess the general fitness of an individual and population.”
Management implications
The Bureau of Land Management considers the swift fox a sensitive species, and Buxbaum’s project is part of a larger effort to understand how swift fox populations respond to habitat changes. Her research may ultimately have implications for swift fox management in areas experiencing ground disturbance associated with energy development.
“It’s a great opportunity because not only are we learning more about the fundamentals of swift fox ecology and life history, but we’re also working hand in hand with the Bureau of Land Management to better manage landscapes for swift fox,” Buxbaum comments.
To learn more, contact faculty advisor Joe Holbrook at joe.holbrook@uwyo.edu.
This article was originally published in the 2024 issue of Reflections, the annual research magazine published by the UW College of Agriculture, Life Sciences and Natural Resources.
