was “near extinction, and the primary cause is almost certainly poisoning campaigns among the prairie dogs,” asserting that “far more animals are being killed than would be required for effective protection of livestock, agricultural crops, wildlife resources, and human health.”
By 1964, the U.S. Bureau of Sport Fisheries and Wildlife (predecessor of the U.S. Fish and Wildlife Service) was still poisoning more than a quarter-million acres of prairie dogs per year, but South Dakota still had some remnant prairie dog colonies. As eloquently described by Faith McNulty in the book Must They Die?, bureau employees in South Dakota like Bill Pullins were pulled in two directions. While still mandated to assist in the extirpation of prairie dogs, bureau employees also were increasingly thinking about conserving the black-footed ferret, wondering why there were so few ferrets and what could be done to increase their numbers.
Even with this newfound interest in studying ferrets, there were very few known populations left to study. The first official study of ferrets was done on Earl Adrian’s ranch a few miles south of White River, South Dakota, where they had been spotted in 1964. South Dakota Game, Fish and Parks biologist Bob Henderson had a passion to study the rare mammal, but his boss allowed him to take up the hobby only if it did not interfere with his other duties. Henderson promised to keep his ferret studies under the radar, but even so, Earl Adrian didn’t want a government employee on his land. Instead, he forced Henderson and his colleague, Dr. Paul Springer at the South Dakota Cooperative Fish and Wildlife Research Unit, to hire his son, Dick Adrian, to conduct the study.
Bob Henderson and Dick Adrian set up camp on a southern prairie dog colony on the family ranch and observed ferrets day and night from August 1964 to August 1965. They were the first researchers to use spotlights at night to find the reclusive animal, watch its behavior, and learn about its ecology. True to the original 1929 description by Ernest Thompson Seton, a ferret is “like a mouse in cheese, for the hapless prairie dogs are its favorite food.” Ferrets never left the prairie dog colonies, only coming out of the labyrinth of underground prairie dog burrows for a few hours during the night, hiding behaviors from the researchers who could only guess how they killed prairie dogs and reared their young. On occasion, the researchers saw a female ferret move her litter across the prairie dog town single file like a “toy train.” In the end, like so many wildlife studies, they raised more questions than answers, still wondering how often ferrets dispersed between colonies, and asking a question that still puzzles ecologists: How many prairie dogs does a ferret require?
At the same time, the critical question was how many other ferret populations existed. Black-footed ferret sightings became increasingly rare. Hundreds of letters came in with word-of-mouth stories of ferret-like creatures that almost always sounded more like confusion with the common long-tailed weasel. Sightings were reported in Kansas, Utah, Montana, Wyoming, and Manitoba. In the official record, the majority of ferret sightings occurred in South Dakota. Yet even in South Dakota, confirmed ferret sightings were rare. Never more than twelve in a year, and of all confirmed sightings between 1950 and 1972, more than 58 percent were from Mellette County, where Bob Henderson and the growing ferret research team focused their attention.
The following summer, Dick Adrian quit the ferret project and was replaced by Con Hillman, an ambitious North Dakota farm boy with a bachelor’s degree in wildlife management from Utah State University. Con was keen to make the study of ferrets in South Dakota part of his master’s degree research, and in July 1966 he found a female with a litter of five on a ranch owned by Jim Carr. Over the next sixteen months he would find sixteen more, following a total of three litters around in the night and making careful notes of their behaviors: where they moved, what they ate, and patiently waiting by their burrows to see how long they stayed underground. He reported his research as a master’s thesis defended at South Dakota State University in 1968, and that same year summarized his findings for the public in the short, pioneering paper hidden on the 433rd page of the Transactions from the 33rd Annual North American Wildlife Congress unassumingly titled “Field Observation of Black-Footed Ferrets in South Dakota.”
As I moved forward through the attic file boxes into 1968, 1969, and 1970, reports from South Dakota became more frequently typed and official sounding. A series of scientific publications and symposium proceedings were produced by Con Hillman, Bob Henderson, and a variety of other biologists who collaborated in Mellette County ferret research. I pulled out details from scientific papers showing that scat analyses proved that ferrets almost exclusively fed on prairie dogs. Monitoring reports showed that ferrets rarely left prairie dogs colonies and that they required sizeable prairie dog colonies of at least twenty-five acres in size, and more likely close to a hundred acres in size. All told, during the eleven years of studying ferrets in Mellette County, ninety ferrets were located, and at least thirty-eight young were produced. Yet rather than acting as a single, large, healthy population, the ninety confirmed ferrets were highly dispersed across Mellette and the surrounding eight counties—evidence that this wasn’t the last stronghold but rather just the last fragments of a species on the decline.
Although the meat of the scientific reports on ferrets in Mellette County was focused on methodology and reporting results, the final concluding paragraphs began to consistently end with increased calls for ferret and prairie dog conservation. Poisoning continued throughout much of South Dakota as federal agencies contradicted each other and state and local farm bureaus continued to lobby for prairie dog control. State governors, congressmen, and even biologists continued to believe that prairie dogs were pests to be eradicated. Concessions were sometimes made to at least look for ferrets prior to poisoning—to “clear” the area and confirm that ferrets did not exist where poisoning was to occur. Unfortunately, the surveys were often done during the day and by untrained personnel with prairie dog vendettas. Even if done correctly by those who had actually seen a ferret in the wild, it would have been difficult to find a reclusive ferret during a quick prairie dog “clearance” survey. Thus by claiming to not see a ferret, biologists were able to justify their poisoning of prairie dogs on thousands of acres of ferret habitat on private and public lands. By 1968, a frustrated Robert Henderson left South Dakota. Dr. Springer was reassigned to North Dakota.
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While Con and others were undertaking that first detailed study of ferrets, in October 1966, the Endangered Species Preservation Act was passed by Congress, extending full protection to thirty-six birds, six reptiles and amphibians, twenty-two fish, and fourteen mammals, including the black-footed ferret. That year, funds were appropriated for Dr. Ray Erickson, Assistant Director of Endangered Wildlife Research for the Bureau of Sport Fisheries and Wildlife, to start a captive population of black-footed ferrets at Patuxent Wildlife Research Center on the far side of the country. More than two decades before my father started work there, Patuxent was world renowned because of its history of innovative, successful captive breeding programs for critically endangered whooping cranes, bald eagles, and California condors.
Ray Erickson didn’t get his first batch of wild black-footed ferrets until 1971, when six ferrets were captured from Mellette County and taken to Patuxent. Between 1968 and 1971, Patuxent staff had been practicing by raising European polecats, a stubby-bodied Eurasian ferret species that is the black-footed ferret’s closest living relative. Over three years, they had remarkable success, producing more than 150 offspring and testing breeding and weaning procedures, canine distemper vaccines, and designs for nest boxes and holding pens.
Of the six ferrets transported from South Dakota, four died from a modified live-virus canine distemper vaccine before even arriving at Patuxent. It was a vaccine that worked well on European polecats to prevent a disease now known to be 100 percent fatal to black-footed ferrets. But black-footed ferrets were sensitive to the live-virus treatment, and only males FM-71–1 and FM-71–2 survived.
On September 15, 1972, Con Hillman captured female ferret FF-72–1, injected her with a killed canine distemper virus vaccine this time, and drove her to a secure National Guard compound in Rapid City, South Dakota, for a three-week quarantine. After surviving her period of isolation, on October 4, the female ferret
