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Swift fox populations growing in Wyoming

A swift fox eyes its watcher in the Shirley Basin south of Casper. Once at risk of disappearing from the landscape, swift foxes are growing in numbers and expanding their range thanks to conservation efforts in Wyoming.

A little-known species in Wyoming is smaller than the average house cat but part of a big conservation success story.

Once hunted and with populations at risk, swift foxes in Wyoming have been growing in numbers and expanding their range, giving hope to researchers and wildlife officials.

These tiny foxes are a little known but valuable part of the grasslands and desert ecosystems of Wyoming. Conservationists and wildlife officials hope that with monitoring and reintroduction efforts in Montana the canine will become a modern-day ecosystem triumph.

“They have gone through a bit of a decline, historically, and more recently seem to be doing fairly well … even in some areas where we hadn’t historically even thought they were present, so that’s been very exciting,” said Nicole Bjornlie, a nongame biologist for the Wyoming Game and Fish Department.

Weighing only five pounds on average, the swift fox is the smallest fox species in North America and the smallest member of the canid family.

Historically found across western North America, these foxes were thought to occupy the eastern part of the state and can still be found there in small numbers.

“Areas that we would consider our Great Plains grasslands and that transition area into the sagebrush basins, we know they’re there,” Bjornlie said. “We’ve been documenting them.”

Swift fox numbers in the United States and Canada saw a dramatic decline about the turn of the last century due to anti-predator campaigns and habitat changes from agricultural, industrial and urban development.

Swift foxes are now considered a “species of greatest conservation need” in Wyoming, Bjornlie said.

“They’re one of our native species in the state,” Bjornlie said. “But one that isn’t as often seen or really thought of by the public and that’s why we are interested in keeping track of them.”

Efforts have been made in recent decades to preserve remaining swift fox populations, including a failed petition for swift foxes to be listed as an endangered species in the 1990s, according to Bjornlie.

“Research found that, actually, they were more widespread than they had originally thought,” Bjornlie said. “Definitely a good news scenario. … And they haven’t been a concern at the national level.”

However, state agencies and wildlife officials have still been monitoring swift fox populations in several states and participating in reintroduction and conservation initiatives. Some Wyoming swift foxes are being used to further conservation and reintroduce populations to Montana.

“All of the state agencies within the fox range are participants in the fox conservation team,” Bjornlie said. “We meet every other year … trying to keep tabs on how things are going.”

Their work seems to be paying off. In Wyoming wildlife officials are beginning to see an increase in swift fox populations, with more frequent sightings across the state.

“The fact that we have them there, and they seem to be showing up more often, is really exciting,” Bjornlie said.

Wyoming swift foxes also seem to even be expanding beyond their historic range into higher-elevation areas like Big Piney and Pinedale, according to Bjornlie.

“The fact that we’ve got them showing up in areas where we’d never thought they were historically is a really interesting biological, ecological question,” Bjornlie said.

Researchers and wildlife officials are currently using occupancy modeling to try to monitor swift fox population expansion and to hopefully bring understanding to what is causing this change in the foxes’ habitat range.

“Basically, we’re monitoring changes in their overall distribution,” Bjornlie said. “We can get an idea of where we’re starting to see them where we haven’t in the past … We can kind of tease apart what might be happening at habitat level that could be driving where they’re expanding to or where they could be disappearing.”

In addition, wildlife officials are hoping to use other methods to get an estimate of swift fox numbers across the state.

“We’re hoping that maybe we can start to use some genetics from scat at our monitoring locations to get an idea of how many individuals seem to be showing up within a given area and maybe start to make some extrapolations to the state,” Bjornlie said.

Hila Shamon, a research ecologist with the Smithsonian Conservation Biology Institute, is working to reintroduce swift foxes on the Fort Belknap Indian Reservation in Montana.

Shamon and her research team are trying to reconnect isolated swift fox populations and reestablish their historical range.

“A lot of our research is focused on the conservation and restoration of these temperate grasslands,” Shamon said. “Because temperate grasslands are the most threatened biomes on Earth, and the least protected.”

“We have a lot of work to do to restore and protect this unique ecosystem and all those beautiful critters that occur there,” Shamon said.

Part of that work involves the reintroduction of swift foxes to the area to restore balance to the ecosystem, similar to the successful reestablishment of wolf populations in Yellowstone.

“An ecosystem is like a web of interactions and relationships between other species,” Shamon said. “Swift foxes … they regulate in that ecosystem. And when there’s a missing link, then things are not in balance.”

Last year Shamon’s team reintroduced its first 27 foxes, which had been captured from Wyoming, on the reservation.

“The idea is a five-year program,” Shamon said. “Every year based on our models we need to reintroduce somewhere between 40 to 50 individuals for a period of five years, so we can have a 90% chance of success, to establish a population that will exist into the future.”

Today swift foxes occur in about 40% of their historic range, according to Shamon, but there is still a lot of work to be done to ensure the continued survival of swift fox populations in Wyoming.

“We’re only now starting to understand what is so unique about these swift foxes,” Shamon said. “Maybe there are things that we didn’t know about them because they were eliminated before we even studied them.”

Contact Analeise S. Mayor at 732-7076 or This story is supported by a grant through Wyoming EPSCoR and the National Science Foundation.

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