INTERIOR, S.D. – On the grasslands a few miles from the pinnacles and spires of Badlands National Park, federal wildlife officials have been waging a war since spring to save one of the nation's largest colonies of endangered black-footed ferrets.
The deadly disease sylvatic plague was discovered in May in a huge prairie dog town in the Conata Basin. The black-tailed prairie dog is the main prey of ferrets, and the disease quickly killed up to a third of the area's 290 ferrets along with prairie dogs.
The disease stopped spreading with the arrival of summer's hot, dry weather, but it poses a serious threat to efforts to establish stable populations of one of the nation's rarest mammals, said Scott Larson of the U.S. Fish and Wildlife Service in Pierre.
The plague, which is carried by fleas, is the biggest danger to ferrets' survival in the Conata Basin and other sites that still have ferrets, said Larson, who is coordinating ferret conservation efforts among five federal agencies.
"It has the capacity to take out more ferret habitat than anything we've run up against, and do it in such a short order," Larson said. "For ferrets, it's the most challenging issue we face."
The ferrets were once considered extinct. But one colony was discovered in Wyoming in 1981, and a captive breeding program succeeded in increasing their numbers. Since then, ferrets have been reintroduced at 17 sites in South Dakota, Wyoming, Montana, Colorado, Utah, Kansas and Mexico, said Nancy Warren, endangered species program leader in the Rocky Mountain Region of the U.S. Forest Service.
Reintroduction efforts failed in some locations, and plague has hit most of the ferret colonies to some degree, Larson said.
Establishing many reintroduction sites helps protect the overall ferret population from being wiped out by plague, Larson said. "I guess it's the old risk management of having your eggs spread out among many baskets."
Representatives of federal agencies and some conservation groups have taken a double-barreled approach to try to stop the spread of plague and save prairie dogs and ferrets in the 20-mile-long Conata Basin, a portion of the Buffalo Gap National Grasslands that lies just south of the Badlands in southwestern South Dakota.
This summer, a crew of four has buzzed across the prairie on all-terrain vehicles, pausing frequently to spray white insecticide dust into prairie dog burrows to kill fleas.
After dark, another crew moved into the area during part of the summer to shine spotlights across the grasslands, trap ferrets and vaccinate them against the plague.
Officials want to dust about 11,000 acres with insecticide by this fall, and have covered about two-thirds of that area so far. More than 60 ferrets have been vaccinated, with 15 of them already getting the desired two doses.
Of the 25,000 acres of prairie dog habitat managed for ferrets in the basin, the plague had spread to about 9,700 acres before its growth halted in August. Officials expect the plague might start spreading again this fall or next spring. The disease has not been found inside Badlands National Park itself.
Warren said the insecticide appears to be effective, but it's too early to tell if it will save the ferrets.
"We're learning as we go. We really don't know the answer to that yet," Warren said. "We're hopeful with the dusting, which is something new we're doing now, we'll be able to at least contain the extent of this plague."
The basin also has been the focus of controversy as the Forest Service tries to balance the protection of prairie dogs and ferrets with the needs of ranchers who graze cattle on leased sections of the national grasslands.
Prairie dogs once were routinely poisoned as pests. However, the rodents expanded rapidly in the region, moving from federal land to private ranches, during an extended drought and a halt to poisoning on federal land while government officials considered whether they should be protected under the Endangered Species Act. The Fish and Wildlife Service decided in 2004 not to protect prairie dogs, but the agency is now reconsidering the issue.
Jonathan Proctor, Great Plains representative for Defenders of Wildlife, a conservation group, said the Conata Basin is the last remaining large complex of black-tailed prairie dogs on the Great Plains since the plague destroyed two in Montana and Wyoming. Prairie dogs must be protected because they are important not only to ferrets, but also to hawks, burrowing owls and many other species, he said.
"Even with the loss of almost 10,000 acres of prairie dogs, Conata Basin still remains the largest and most important prairie dog complex on federal lands in the Great Plains. It's worth all these efforts to save it," Proctor said.
But Shirley Kudma, who ranches in the basin with her husband, Donald, said the prevalence of plague confirms the predictions of ranchers overrun by prairie dogs in the past decade. They argued more should have been done to limit the spread of prairie dogs because the hungry rodents strip the ground of grass and leave little for cattle.
"Nature took care of it, didn't it?" Shirley Kudma said. "There's the plague and the prairie dogs, and that's nature taking care of the expansion."
Ranchers don't want to wipe out prairie dogs, she said.
"I think we want to get along. We want to be able to survive just the same as the prairie dogs want to survive. We don't want to annihilate them. We don't. Just get them under control so they're not sick. Give the ferrets something healthy to eat."
About 5 to 15 people are infected by plague in the United States each year, but it can be cured with antibiotics if treatment is prompt.