The area of plague-infected black-tailed prairie dogs has more than doubled in western South Dakota since mid-May, and the disease could begin to seriously hurt the state's population of endangered black-footed ferrets.
Plague is almost always fatal to infected prairie dogs and has killed a large number of the rodents, wildlife experts said. Black-footed ferrets hunt and dine almost exclusively on prairie dogs.
"When ferrets eat an infected prairie dog, they'll get a massive dose" of plague, said Kevin Atchley, Wall District ranger for the U.S. Forest Service. "It's likely that some ferrets have perished."
(...)Plague is an infectious disease caused by the bacterium Yersinia pestis. The disease, also known as bubonic plague, spread through the West after it appeared in San Francisco in 1902. It was first detected in South Dakota wildlife in western Custer County in 2004.
The disease is mainly spread through wildlife populations - coyotes being a favored traveling host - by infected fleas that transmit the disease through their bite.
In late May, workers with the U.S. Fish and Wildlife Service, the U.S. Forest Service, the National Park Service and the U.S. Department of Agriculture's Animal and Plant Health Inspection Service began dusting prairie dog towns with insecticide to kill the fleas but keep the ferret's preferred food source alive.
The insecticide, similar to what is given to dogs and cats to control fleas, is released via a wand sprayer from a tank mounted on an all-terrain vehicle. Workers stick the wand down each burrow entrance to release the dust. As the prairie dogs enter and exit, the dust is rubbed into the fur and kills the fleas.
As of last week, workers dusted 2,440 acres of prairie dog towns, including 700 acres within Badlands National Park.
(...)We've dusted specific areas to hold onto our good, productive ferret areas," said Scott Larson, spokesman for the U.S. Fish and Wildlife Service in Pierre. "We think it's taken out a lot of the prairie dog population, and a lot of that (area) is occupied by ferrets."
"We'll spray one-third of the colonies to protect two-thirds of the ferret population," Atchley said.
Yet the threat remains for the black-footed ferret, once thought to be extinct but now representing one of the most successful reintroduction efforts of wild animals back into a species' historical range. For the black-footed ferret, that range included grassland habitats in 12 U.S. states, two Canadian provinces and possibly northern Mexico.
The last wild ferrets - Fish and Wildlife Service officials called them the rarest 18 mammals on Earth - were captured in Wyoming in 1987 to begin the breeding and reintroduction program. There are an estimated 600 to 800 ferrets now living at 15 reintroduction sites.
Foto: Mike Lockhart
About 300 ferrets live within the Conata Basin - considered by wildlife advocates to be the most successful of all the sites.
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