Endangered Ferrets Gain Colorado Foothold

Brian Handwerk
for National Geographic News

September 26, 2005

A midnight survey has shed light on a surprising success story for black-footed ferret reintroduction in Colorado.

The ferrets, perhaps North America's most endangered mammals, have been released in the state since 2001 as part of a national reintroduction program. But Until August scientists had little data to document their success.

"It was a real boost for our morale," said Pam Schnurr, a wildlife conservation biologist with the Colorado Division of Wildlife in Grand Junction.

Biologists searched about half of northwestern Colorado's 20,000-acre (8,000-hectare) Wolf Creek Management Area. Scientists and volunteers walked the rugged terrain for nine nights with high-powered spotlights to spot the reclusive nocturnal animals.

Five ferret sightings were confirmed—including a lactating female who had given birth earlier in the summer. Another five animals were spotted but not confirmed.

While those numbers might seem low, they suggest that a significant population exists in the region.

"The ferrets are only out for maybe 15 to 20 minutes every two or three nights, so the odds of us coming upon one are low. That's why we were so encouraged with these results," Schnurr said.

"The fact that we saw so many means that there are a lot more out there."

Back From the Brink?

The U.S. Fish and Wildlife Service lists the black-footed ferret (Mustela nigripes) as an endangered species.

The sleek masked predators dine almost exclusively on prairie dogs. Ferrets co-habitate with their prey in extensive underground warrens known as prairie dog towns.

The ferret population took a major hit when prairie dogs came under assault as agricultural pests during settlement of North America's grasslands in the 1920s and '30s.

In addition to prairie dog eradication programs and habitat loss, several devastating outbreaks of sylvatic plague—the animal equivalent of bubonic plague—greatly reduced ferret populations.

Scientists estimate the ferrets once occupied prairie dog towns spread between northern Mexico and southern Canada and west from the Rocky Mountains into the Great Plains. Now the animal is limited to a fragmented 5 percent of its traditional range.

In 1979 scientists declared the black-footed ferret extinct. But in 1981 a ranch dog turned up with a dead ferret in its mouth. The find eventually led scientists to a group of 129 animals living near Meeteetse, Wyoming.

When an outbreak of canine distemper reduced those numbers to 18 in 1986, the surviving animals were captured and used to begin a captive breeding program.

In successive years about 3,000 ferrets have been bred in the program and released in Wyoming, South Dakota, Montana, Arizona, and Colorado.

Despite the most recent glimmer of hope, in general the results have been mixed.

"Overall, I hate to say it, but it's been mostly bad news," said Bob McCready, director of the Nature Conservancy's Prairie Wings program. The program works to preserve U.S. grasslands for endangered birds and other prairie species.

"In the vast majority of reintroduction sites [the ferrets] just haven't had the ability to sustain a viable population," he said. "The only site that has had really, really good success is the Conata Basin, just south of the Badlands in South Dakota."

But in recent weeks even the news from Conata has been bad. A sylvatic plague outbreak has been confirmed just 30 miles (48 kilometers) from the previously plague-free site, and scientists have issued a call for help.

Volunteers are hand-dusting prairie dog burrows with flea-killing pesticides in hopes of checking the outbreak in what has been the animals' greatest stronghold.

"It couldn't be worse news quite honestly," McCready said.

Perhaps only 400 ferrets live in all of the states where the release program is ongoing, though no one knows how many may live in Colorado's Wolf Creek area.

Prairie Dog Trap

Across the plains, the battle rages to protect ferrets and prairie dogs. But not everyone is interested in fighting on the side of the animals.

In grassland areas like South Dakota ranchers fear lost livelihoods as prairie dogs decimate grazing lands by devouring vegetation.

In dry years, which have been common since 2000, the animals expand their territory in search of food. In some places the land left behind resembles a moonscape.

"There's an intense line between those who think that the only good prairie dog is a dead prairie dog and those who think that every prairie dog should be protected," said the Colorado Division of Wildlife's Schnurr. "That's the range that we deal with."

The U.S. Forest Service and various legislative bodies have alternatively banned and supported poisoning and other removal methods. In general, government involvement makes many locals uncomfortable.

"It took approximately ten years to get the local community on board with the idea of introducing an endangered mammal in the [Wolf Creek] area," Schnurr said. "Everybody is worried about property rights and the effects it will have on their way of living."

Meanwhile conservationists worry that a unique opportunity to save the ferrets could slip through their grasp.

"It's a very rare opportunity to attempt to save a species whose numbers are that reduced," said the Nature Conservancy's McCready. "Is it feasible?"

But McCready remains inspired by the ferret's tenacity.

"It's pretty spectacular when all of a sudden you discover something that 99 percent of people felt was extinct. You feel like you have a second life."

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