Utah Division of Wildlife Resources

Black-footed ferrets released in Utah and Colorado

Biologist look for answers to sylvatic plague that affects ferrets.

VERNAL — On Nov. 21, biologists and members of the public released black-footed ferrets at two sites — Wolf Creek in Colorado and Snake John Reef in Utah.

The ferrets they released will do more than increase the size of ferret populations that are already in the two areas — they may help biologists develop a vaccine that will protect ferrets from sylvatic plague.

Similar to black plague in humans, sylvatic plague can wipe out a ferret population.

"The 10 ferrets released into Snake John are part of a larger study to determine the effectiveness of a vaccine developed for the sylvatic plague, which is the prairie dog version of the black plague," says Brian Maxfield, sensitive species biologist with the Utah Division of Wildlife Resources.

"The black-footed ferret preys almost exclusively on prairie dogs, so large colonies of prairie dogs are essential to the ferrets. Unfortunately, neither the ferret nor its prey have natural immunities to the plague. An outbreak can wipe out entire colonies."

The Utah and Colorado sites are two of four sites that a biological team working for the U.S. Geological Survey have designated in the vaccination study.

"The study started in 2004," Maxfield says. "As part of the study, we get about 20 animals a year. The vaccine is given to half of the animals. The other half are 'control' animals that are not vaccinated.

"So far, it looks like a success. We know we have plague at low levels in the Utah-Colorado area, but there hasn't been a serious outbreak at these release sites."

Maxfield says the best information about plague comes from a plague outbreak in prairie dogs at the Charles Russell National Wildlife Refuge, a ferret reintroduction site in Montana. "Part of the ferret colony died, but it seems like the vaccine saved most of the ferrets that were vaccinated," he says.

In addition to the vaccine study, the ferrets released at Snake John will help the overall reintroduction efforts in the area.

"We released these ferrets in the Snake John area to help supplement a small, wild ferret population that's already there," Maxfield says. "A few years ago we started receiving reports from motorists who saw ferrets crossing Highway 40. We checked and verified those reports.

"The Snake John area has several good-sized prairie dog colonies. And it also falls within the Black-footed Ferret Management Plan area, so we're able to release additional ferrets into the area. The new ferrets should help increase the genetic pool and give this small population a boost."

Maxfield says the Snake John ferrets likely originated from Coyote Basin, where ferrets were reintroduced in 1999.

"Snake John is roughly eight to 10 air miles from Coyote Basin, but it would take a ferret roughly 30 miles to make its way there on the ground," Maxfield says. "In the 16 or so colonies of prairie dogs in the Snake John area, we've seen ferrets in four. And we've caught ferrets in two of the largest colonies.

"So far, none of the ferrets we've caught have been marked, so these have to be wild-born ferrets at least a generation away from a released animal."

The ferrets have also done well around the main release site in Coyote Basin. "We've documented ferrets in the eight largest prairie dog colonies closest to the Coyote Basin release site," Maxfield says. "In almost every one, we've confirmed that the ferrets are reproducing in the wild."

Black-footed ferret history

According to reports, the black-footed ferret was the last mammal discovered on the North American continent. That's quite a statement considering the evidence that was eventually found: fossils, skins, body parts and occasional sightings of the animal indicate they once inhabited at least 12 Western states, southern Canada and northern Mexico.

So why did it take so long to discover them?

These small members of the weasel family are nocturnal (meaning they're active mostly at night), and they live most of their lives underground inside prairie-dog holes.

They were discovered in time to watch the last known colony in South Dakota die out. After years of searching for another colony, black-footed ferrets were declared extinct in 1967.

Ferrets weren't rediscovered until 1981, when a rancher took an unusual animal his dog had killed the night before into a small store in Meeteetse, Wyoming.

Fortunately the storeowner had kept a business card from a searcher who had asked the storeowner questions about an animal like the ferret a few months earlier. The storeowner's call led to the discovery of a small population of black-footed ferrets.

From 1981 to 1985, this small population expanded to 129 animals. Then, in 1985, the population crashed when distemper and the plague ravished the ferrets and a colony of prairie dogs the ferrets were preying on.

The black-footed ferret quickly became the most endangered mammal on earth. It looked like it was destined to be declared extinct one more time.

Biologists collected the last 18 known animals between 1985 and 1986 and began an emergency-breeding program. At first the breeding program failed because most of the ferrets were too young to breed successfully. Fortunately, the last ferret collected was an older male who knew how to breed successfully.

Today, six breeding facilities produce roughly 300 to 350 kits (baby ferrets) per year. About a third of the kits are kept in captivity to breed future generations. The others are released into the wild.

Utah's connection

In the late 1980s and early 1990s, Utah began mapping prairie dog colonies in the state. After the colonies were mapped, two areas were identified as potential reintroduction sites for black-footed ferrets: the Cisco Desert and Coyote Basin.

When an outbreak of plague hit the Cisco prairie dog population, Coyote Basin in northeastern Utah became the state's primary release site.

At the same time, similar sites were also being identified in Colorado. The two states share prairie dog complexes, so Utah and Colorado, along with federal agencies and interested universities, joined forces to create the Colorado-Utah Black-footed Ferret Reintroduction Working Group.

Under the guidance of a biologist from the Utah Division of Wildlife Resources, government agencies, local businesses, interested organizations and individuals formed a committee in 1992 to write the "Cooperative Plan for the Reintroduction and Management of the black-footed ferret in Coyote Basin, Uintah County, Utah."

After numerous scoping meetings, committee discussions, public reviews and comments, a plan was created. The plan was signed in 1997.

The key to the plan's success was the federal government giving a large area with known prairie dog colonies a 10 (j) designation under the Endangered Species Act (ESA). Under a 10 (j) designation, any ferrets reintroduced to the area would be considered part of a nonessential-experimental population.

After reviewing the plan, in 1998 the U.S. Fish and Wildlife Service declared all of Uintah and Duchesne counties 10 (j) for black-footed ferrets. This designation protects the counties and allows continued activities and development on public lands without the risk of violating the ESA, even if a wild population of ferrets is discovered later.

In the fall of 1999, 71 ferrets were reintroduced into Coyote Basin.

Later that winter, biologists conducted a survey. They found only a half a dozen ferrets. And they found only two ferrets during a survey the following spring.

Because of the low numbers, the working group wondered if the release had failed. Then, during a survey that summer, the biologists found nine adults and three kits. At least two of the adults were clearly females with kits.

With clear evidence of reproduction, Coyote Basin has shown some of the best success of any release site. In the fall of 2000, another 67 ferrets were reintroduced to the area. Between 1999 and the most current release in November 2007, 313 ferrets have been reintroduced into Coyote Basin and the surrounding area of Snake John.

Today

Since the 1999 release, the Coyote Basin ferrets have survived the worst drought in Utah's history and brushes with plague and other diseases. They have also expanded their range to prairie dog colonies on the edges of their introduction site, including Snake John, which is eight to 10 air miles away.

The work isn't done however. While biologists are breathing easier, they also know complications that have happened at other release sites could easily happen here.

To successfully bring an animal that was once considered the most endangered mammal on earth back will depend not only on raising and releasing animals from captive facilities, but also on protecting and enhancing prairie dog colonies and reintroducing ferrets to new sites