Black-Footed Ferret Recovery Faces Major Set-Backs

Black-footed ferrets, in the best of times, are elusive creatures. In addition to maintaining low populations and leading quiet lives, ferrets are most active at night, making studying them that much more difficult. Though native to the Great Plains, an area much traveled by pioneers and explorers during America’s early years, the existence of black-footed ferrets wasn’t officially recognized by naturalists until 1851.

Fast-forward 100 years to the 1950s, and still not much was known about black-footed ferrets, although it was thought that small populations existed throughout the Great Plains. In 1964, scientists began a study of the only-known population of black-footed ferrets living in southwestern South Dakota. By 1967, the black-footed ferret was listed as an endangered species. In 1974, the population disappeared. It was thought at that time that black-footed ferrets had become extinct.

In 1984, a small population of 130 black-footed ferrets was discovered in northwestern Wyoming. Soon after its discovery, the population was devastated by an outbreak of sylvatic (bubonic) plague and canine distemper. As a drastic measure, researchers took the remaining 18 black-footed ferrets into captivity. In 1987, a captive-breeding program was begun to increase the population of black-footed ferrets. Four years later, in 1991, the first black-footed ferrets were released back into the wild. Since their reintroduction into Wyoming, black-footed ferrets have also been released in Montana, South Dakota, and Arizona.

One of the most successful reintroduction sites is located in South Dakota, in an area just south of Badlands National Park. At one point in time, over half of the U.S. population of black-footed ferrets could be found at this site. That all changed earlier this year when the ferret population there, numbering 300 animals, was decimated by an outbreak of bubonic plague. It is believed that one-third of the population died. Black-footed ferrets are particularly sensitive to the plague and die fairly quickly after becoming infected. The plague is not a new problem for black-footed ferrets (or the colonies of prairie dogs that the black-footed ferrets depend on as their main food source). However, this year’s outbreak has been particularly harsh as the plague thrives in wet conditions. This past spring was particularly rainy, leading to an explosive outbreak of plague within black-footed ferret and prairie dog colonies.

Population loss due to the plague is not the only problem facing black-footed ferret recovery efforts. As mentioned above, prairie dogs are the main food source for black-footed ferrets. Just like ferrets, prairie dogs are also susceptible to outbreaks of the bubonic plague, which is spread throughout the colony by infected fleas. When prairie dog populations decrease due to the plague, so do black-footed ferret populations. However, a greater problem exists for prairie dogs than just the plague. Prairie dogs are considered to be pest species by many ranchers in the Great Plains region. Ranchers complain that prairie dogs denude rangeland of the grasses their cattle need to eat. Some scientists counter-argue that prairie dogs actually help increase the digestibility and protein content of rangeland grasses by acting as natural fertilizers. Regardless, the U.S. Forest Service still maintains an active population control program by poisoning prairie dog populations at the request of ranchers. The U.S. Forest Service is currently considering an expansion of the prairie-dog poisoning program onto land that would be suitable for the reintroduction of black-footed ferrets. An expansion of the prairie-dog control program would mean the loss of prairie dog populations that could feed black-footed ferret populations.

In the mean time, scientists are working to prevent the spread of bubonic plague within colonies of black-footed ferrets and prairie dogs. One effective method has been to dust prairie dog burrows with insecticide that kills the fleas that spread the plague. (In addition to eating prairie dogs, black-footed ferrets also live in abandoned prairie dog burrows.) Another successful method involves inoculating black-footed ferrets with a vaccine that protects the animals from becoming infected with the plague. Scientists hope that these two methods put together will successfully prevent a cataclysmic population crash among black-footed ferrets and keep the animals on the path to recovery.

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