Saving Species: The Black-Footed Ferret

by Karl Hess

Table of Contents

The U.S. Biological Survey--bane of the black-footed ferret--spells its name out in dead prairie dogs in 1921. Despite the fact that the Endangered Species Act is supposed to protect the ferret, the agency's successor continues to kill prairie dogs--the ferret's sole source of food--today.


One hundred years ago, millions of black-footed ferrets thrived in the prairies of the Great Plains and the intermountain West. By the end of 1985, only ten were left. The ferret has become a classic example of a species endangered by human activities.

Unlike species whose ecological relationships are complex and whose declines are puzzling, the black-footed ferret's needs and the reasons for its disappearance are simple. The ferret lives almost exclusively on prairie dogs. It eats prairie dogs, it feeds prairie dogs to its young, and it makes its home in prairie dog burrows. So, for the ferret, the survival equation is simple: Prairie dogs equal life; no prairie dogs equal extinction.

In the last decades of the nineteenth century, western ranchers heavily overgrazed the plains and mountain range. This actually improved prairie dog habitat. Prairie dogs cannot colonize in the dense grasses of ungrazed ranges, but with overgrazing prairie dog colonies grew to cover 700 million acres. Although no one was counting at the time, black-footed ferret numbers also increased to as many as six million.

Growing prairie dog populations were a symptom of overgrazing. But a 1902 federal research report tragically confused cause and effect and blamed the effects of overgrazing on the prairie dogs. This put ranchers on the warpath against prairie dogs.

By themselves, a few ranchers thinly scattered across the West probably could not have done much about prairie dogs. Two Texas ranchers once attacked a prairie dog colony with rifles. For two solid weeks they shot prairie dogs, spending thousands of bullets to kill as many as they could. At the end of that time they couldn't see that they had even made a dent in prairie dog populations.

Strychnine is more effective than bullets, and plowing more effective still at eliminating prairie dog colonies. Using poison and plows, ranchers managed to reduce prairie dogs to about 20 percent of their historic range by 1916. Relying on their own resources, that might have been as much as they could or would do--especially since (as recent research reveals) the benefits to livestock of killing prairie dogs fall short of costs even on the most productive grasslands. As range ecologist Dan Uresk found, "prairie dog control on rangelands in western South Dakota did not result in a positive increase in forage production after 4 years."

But ranchers had a friend to help them in their crusade against prairie dogs: a friend named Uncle Sam. As long as Uncle Sam would pay, it wouldn't matter whether the benefits exceeded the costs. Many of the overgrazed lands were federal, so that's where many of the prairie dogs were found. Since ranchers had to pay the government to use those lands after 1905, they convinced Congress that the government had an obligation to help them wipe out prairie dogs--on both public and private land.

The agency in charge of "controlling" prairie dogs was the U.S. Biological Survey, a branch of the Department of Agriculture. As its name suggests, its original mission was fairly benign: mapping plant communities and counting wildlife populations. But an important law of government is that an agency with a mission that has no constituency will soon find a constituency who will give it a new mission. Ranchers were the constituency, and the mission was to rid the range of predators and prairie dogs.

Congress gave the Survey its new mission in 1916. The Biological Survey attacked this mission with a vengeance, not to mention every poison, trap, and other animal control device modern science could come up with. In just four short years, it had eradicated prairie dogs from 47 million acres, or almost half of their remaining range. By 1960, with the active help of the Forest Service, Bureau of Land Management, Bureau of Indian Affairs, and even the Park Service, the agency had eliminated prairie dogs from all but about 2 percent of their historic range.

An important law of ecology is that, when you go after a prey species, the predators disappear first. With prairie dogs making up 95 percent of its diet, the ferret is an obligate associate of prairie dog colonies. This makes the ferret an indicator species for prairie dog habitat in the same way that the spotted owl is an indicator for old-growth habitat.

Biologists say that well over 100 species, including pronghorn and (at one time) bison, find food and shelter in areas colonized by prairie dogs. Many of these species, including the mountain plover, the ferruginous hawk, and the swift fox, depend on prairie dog colonies as a critical part of their habitat. Several of these species are declining and may be threatened by continuing prairie dog eradication programs.

Although their range is limited, plenty of prairie dogs still survive. But by 1940 remaining prairie dog colonies were so small and so far apart that the far less numerous ferrets were too few to form a viable gene pool. Ferrets suffered from inbreeding and were highly susceptible to diseases such as plague and distemper.

Available information suggests that the ferret met current tests of an "endangered species" well before 1940. By 1973, when the Endangered Species Act was passed, biologists were calling the ferret "the rarest mammal in North America."

Government Failure

Up to this point, the ferret's problems seem to be just another case of greedy and selfish people working in a free market and conflicting with the natural world. In fact, virtually all of the ferret's difficulties stem from government failure, not market failure. If the problem really was just one of individual greed, then passage of the Endangered Species Act should have signaled a turn-around point for the ferret. Biologists knew that the ferret was endangered and they knew why.

Under section 7 of the act, the Biological Survey, Forest Service, and all other federal agencies should have immediately stopped killing prairie dogs. Under section 9 of the act, private landowners who poisoned prairie dogs could have been charged with "taking" any ferrets who depended on those prairie dogs for food. A recovery plan could have promoted the spread of prairie dogs, and in turn, ferrets, across millions of acres of federal land.

That's not what happened. By 1973, the Biological Survey had been incorporated into the Fish & Wildlife Service--the very same agency entrusted with saving the black-footed ferret. For another thirteen years, the Fish & Wildlife Service gave lip service to saving the ferret even as it went out and poisoned prairie dog colonies. Ranchers didn't have to risk being charged with "taking" ferrets when they poisoned prairie dogs--they merely had to ask the agency in charge of protecting ferrets to do it for them.

In 1986, Congress--worried that the Fish & Wildlife Service was not eager enough at its job of killing coyotes and prairie dogs--transferred the Service's animal damage control program to the Department of Agriculture. Under that program, as well as the Forest Service, Bureau of Land Management, and other federal agencies, prairie dog poisoning continues to this day.

Recovery: A Play in Three Acts

Instead of becoming an endangered species success story, the black-footed ferret recovery effort turned into a comedy of errors that would rival Seinfeld (and sometimes the Three Stooges) if it weren't so tragic. It is a comedy with a prologue and three acts.

The prologue begins in 1964, when biologists find a small population of black-footed ferrets in South Dakota. Extensive surveys identify a total of 90 ferrets. Hoping to keep the animal from extinction, biologists monitor the population for seven years. By 1971, the South Dakota ferrets are the last known wild ferrets in existence.

But the ferrets aren't doing well, and their problems are compounded by rising tensions between federal agencies and surrounding landowners. So the Fish & Wildlife Service captures nine ferrets for a captive breeding program. The program gets off to a bad start when a vaccine meant to protect the ferrets against distemper immediately kills four of them.

At this point, act I is heralded by passage of the Endangered Species Act of 1973. The ferret becomes one of the first species listed, and the Fish & Wildlife Service industriously begins to write a recovery plan. Despite the urgent nature of the problem, the plan is not finished until 1978.

Only a few pages long, the plan prescribes five basic steps:

  1. Map the ferret's historic range;
  2. Inventory current ferret habitat;
  3. Estimate past and present ferret populations;
  4. Protect existing ferret populations; and
  5. Restock former habitat using captive-bred ferrets.
By 1978, step 2 is easy: Current habitat is near zero. But the Fish & Wildlife Service flunks step 4: The last-known population in South Dakota had disappeared. Step 5 is also botched: The five captive ferrets breed two litters, but all of the kits die. In 1979, the last captive ferrets also die.

The Fish & Wildlife Service spends the next three years looking for ferrets, to no avail. As far as anyone knows, the black-footed ferret is extinct.

Act II opens in Meeteetse, Wyoming, a ranch community about 30 miles south of Cody. In 1981, a dog belonging to Lucille Hogg, owner of a local cafe, brings to its owner a dead animal that Hogg doesn't recognize. She shows it to a friend, who shows it to a state wildlife manager, who recognizes it as a black-footed ferret.

Immediately, biologists begin combing the area, using a variety of search methods. They soon identify 61 ferrets living on 7,400 acres of prairie dog habitat.

In one of the biggest laughs of the act, Fish & Wildlife Service officials ingratiate themselves to the local populous by threatening to charge Lucille Hogg for letting her dog "take" an endangered species. As a result, ranchers clam up. The New York Zoological Society offers a $10,000 reward for confirmed ferret sightings, but state biologists say that no amount of money would have broken local silence about other possible ferrets. To this day, local biologists believe that more ferrets could have been found if ranchers had cooperated.

Otherwise, the Fish & Wildlife Service doesn't have the budget to do much about the ferrets, so it is happy to let the Wyoming State Game & Fish Department take the lead. The state at least has a better relationship with ranchers, but it decides to do little other than monitor the local prairie dog and ferret populations.

At first, things go well, and the 61 ferrets multiply to 129 by 1984. Some biologists urge the state to capture a few ferrets for breeding and as backup to the wild population. The state declines to do so until 1985, when biologists discover that sylvatic plague is decimating the Meeteetse prairie dog population. Worse, they soon learn that canine distemper is wiping out the ferrets.

In July, 1985, biologists find no new litters and only 58 live ferrets. By October, the ferret population has fallen to 16. Biologists capture six of them and then, in 1986, another dozen, including some from two new litters. Biologists later determine that, during the winter of 1985-1986, the wild population fell to four individuals. Act II closes with eighteen ferrets in captivity and, as far as anyone knows, none in the wild.

Act III begins with the Fish & Wildlife Service writing a new ferret recovery plan. Completed in 1988, the plan calls for:

  1. Breeding a captive population of 200 ferrets by 1991;
  2. Releasing them in ten or more locations; and
  3. Protecting reintroduced populations so that they grow to 1,500 adults by 2010.
Ferrets are bred at Wyoming's Sybille Research Facility and, later, at six zoos scattered across the continent. Captive breeding is more successful than in the 1970s, and by 1991 the agencies have a total of 320 ferrets.

Step two is more difficult, and to date biologists have been able to find only three of the planned ten places to release ferrets. Starting in 1991, biologists released 228 ferrets in southeastern Wyoming's Shirley Basin. Beginning in 1994, another 52 ferrets were released in South Dakota's Badlands. Finally, starting in 1994, 40 ferrets were released in Montana's Charles M. Russell Wildlife Refuge.

Act III contains many slapstick scenes. A government worker transporting ferrets to a release point gets chilled by his vehicle's air conditioning. He turns it off--causing all of the ferrets in his care to die by heat stoke. A contractor capturing prairie dogs to feed captive ferrets manages to get a bunch that are infected with plague. Though many are dead, workers dutifully feed them to the ferrets--with the result that at least two dozen die.

Despite these problems, a total of 304 ferrets have been released into the wild. The captive breeding program has cost more than $12 million, which averages around $40,000 per released animal. But hey--who counts dollars when you are talking about saving an endangered species?

The statistics get grimmer when we count the survival rates of released ferrets: less than 7 percent, or at most twenty animals. For those who insist on counting dollars, that's at least $600,000 per animal.

It turns out that raising ferrets in cages simply doesn't prepare them to survive in the wild. They don't know, for example, to dodge into a burrow when they see a big animal headed their way. Dozens of released ferrets simply become a quick dinner for some lucky coyotes. It may be the most expensive dinner the coyotes ever ate, but that's okay with them because taxpayers paid for it.

Coyotes seem to be the undoing of all but two or three of the ferrets released in South Dakota. In Wyoming, only ten of the 228 released ferrets survived to 1995. Worse, another outbreak of plague appears to have wiped out some 90 percent of the local prairie dog population. Most or all of the remaining ferrets are probably dead of starvation or from getting the plague from their prey.

The greatest success is in Montana, where nine of the forty released ferrets manage to avoid coyotes for at least the first year. The Fish & Wildlife Service plans to release more ferrets in the area in 1996. In an ironic touch, it asks the USDA animal damage control program to first kill all of the local coyotes.

Act III closes with the optimistic feeling that the show isn't over. The captive breeding program goes on, and several hundred ferrets are alive in zoos or the Sybille Facility. Spectators are more depressed by the agency's failure to find more than three sites, or to secure more survivors in the sites it has found. After all, neither the Endangered Species Act nor the Fish & Wildlife Service's recovery plan contemplated saving species by turning them into zoo animals.

Obstacles to Recovery

As director of the Fish & Wildlife Service's black-footed ferret recovery program, Peter Gober coordinates and oversees ferret breeding, release, and protection efforts. Yet he is starting to question the wisdom of putting so much effort into a species whose needs are so specialized that it may need constant attention from people just to survive.

Gober fears that the ferret recovery program is nothing but a classic "Endangered Species Act knee-jerk reaction" and he wonders if society has its priorities confused. Other experts similarly worry that, as Wyoming Game & Fish Department biologists Robert Oakleaf and Robert Luce say, the ferret has "a less than 50-50 chance" of making it in the wild.

These people may be too pessimistic. We have proven that the ferret can be bred in captivity. But if the ferret is to be more than just a zoo piece, its protectors must overcome two types of barriers to recovery: biological and political.

The first biological barrier is predation. One Fish & Wildlife Service biologist, Randy Matchett, says taking ferrets out of cages and releasing them in the wild "is like turning a five-year-old kid out in the jungle." In fact, some of those that didn't get caught by coyotes simply starved to death because they didn't know how to hunt for food.

One solution is to raise ferrets in a more natural environment rather than in cages. This environment could teach them to hunt and condition them to avoid predators. Matchett would also like to erect a temporary electric fence around release sites. This wouldn't provide complete protection, but it could give ferrets a chance to adjust to their new homes before they get picked off by coyotes.

Unfortunately, the value of these ideas is obscured by political pressure to kill coyotes. Ranchers see the ferret program as an opportunity to direct more dollars into coyote eradication. Under pressure from the state of Montana and Montana Senator Conrad Burns, the Fish & Wildlife Service decided to go for this idea.

In reality, coyote killing could do more harm than good. Any coyotes killed are likely to be replaced by other coyotes who move into the empty territory of the dead one. Since coyotes carry distemper, and their fleas carry plague, killing coyotes may just increase the chances that ferrets and prairie dogs will be exposed to disease.

Disease remains an intractable problem even if complete coyote protection is possible. And an even more serious biological problem in the long run is the small gene pool of remaining ferrets. The eighteen Meeteetse ferrets captured in 1985 and 1986 were descended from just five individuals. One of those individuals has bequeathed to recent generations of captive-bred ferrets such defects as kinked tails, jaw and tooth deformities, single kidneys, and females with half their reproductive organs missing. Even if these defects are culled out, the tiny gene pool may make it difficult for reintroduced ferrets to adapt to the wide range of environmental conditions that were inhabited by the original ferret population.

In the end, only persistence and the experience of repeated trials will be needed to overcome the biological obstacles. But this makes the political obstacles particularly frustrating, because some of those obstacles stand in the way of more releases.

The Fish & Wildlife Service didn't pick Shirley Basin, the Badlands, and the Russell Refuge because they were the best sites available. In fact, the first site, Shirley Basin, was probably one of the poorest sites available. First, it was inhabited by white-tailed prairie dogs, whose population densities are typically half of their black-tailed prairie dog cousins. This means that the site is less likely to support a genetically viable population of ferrets.

If that weren't bad enough, biologists knew that Shirley Basin had a long history of plague and distemper. Thus, the disease that probably wiped out the last ten ferrets on the site probably would have gotten them all even if coyotes hadn't eaten the rest.

Despite these drawbacks, Shirley Basin was picked for reasons of political expediency. Better sites were available, including some on Forest Service land, but local ranchers and even the Forest Service objected to those sites. In fact, the white-tailed prairie dog's low population density was a political point in Shirley Basin's favor because it meant local ranchers were less antagonistic to the prairie dogs.

Political objections have also prevented the expansion of the Badlands reintroduction into nearby Buffalo Gap National Grassland, even though this expansion was originally agreed to by Forest Service managers and local ranchers. Similar political problems have kept the Fish & Wildlife Service from finding seven more release sites, as planned in the ferret's recovery program.

These political problems are complicated by strains in the relationships between state and federal wildlife and land management agencies. Federal officials accuse state wildlife managers of maintaining cozy relationships with ranchers. State officials accuse federal managers of alienating local citizens. These tensions make it nearly impossible to set funding priorities, which may be one reason why millions have been spent on captive breeding while nearly nothing has been spent on habitat conservation.

Overriding all of this infighting is the fact that nearly everyone is treating the symptoms, not the causes, of ferret decline. Biologists early on decided to focus on breeding and reintroducing ferrets rather than expanding ferret habitat. This may have been necessary when only eighteen animals existed, but meanwhile the USDA animal damage control program, the Forest Service, and state agencies have continued to eradicate prairie dogs--often in locations near or adjacent to proposed ferret reintroduction sites.

For example, one reintroduction site that most biologists considered superior to Wyoming's Shirley Basin is in Campbell County, Wyoming. Since 1991, when reintroduction began in Shirley Basin, Campbell County has eradicated prairie dogs on at least 50,000 acres of federal, state, and private land. It is almost as if county officials decided to rid themselves of the prairie dog while they could--using state and federal funds, of course--in order to prevent any ferret reintroduction from ever taking place.

Ranchers might still want to kill prairie dogs if federal subsidies to eradication programs were eliminated. But their tendency to do so would be reduced even further if other federal grazing subsidies were ended. These subsidies encourage overgrazing, which encourages prairie dog population explosions, which encourage ranchers to want to kill prairie dogs. Experience in Badlands National Park and various wildlife refuges has shown that stable prairie dog populations are compatible with grazing at rates that would be profitable to unsubsidized ranchers.

Reforming the Recovery

So what must be done to promote recovery of the ferret and insure protection for all of the other species that depend on prairie dog habitat? The first rule is always to do no harm. This means ending all federal and state subsidies to prairie dog control programs. It also means ending federal subsidies to grazing in general, which would lead to more conservative grazing regimes that are more compatible with prairie dog ecosystems.

A second important rule should be for agencies to make better sense of their mission and funding priorities. With 300-plus ferrets in Sybille and various zoos, the species is, for the moment, out of danger. Instead of feeding those ferrets to coyotes, federal and state agencies should work towards habitat protection and expansion.

A third important goal is to get the support of local residents for endangered species protection and reintroductions. As loathe as environmentalists are to admit it, this will almost certainly require revisions of the Endangered Species Act to replace punitive measures with incentives, particularly when dealing with private land. Any short-term benefits that accrue to listed plants and animals through the threatening or taking of private property will be outweighed by long-term opposition to or interference with species recovery.

Another way to encourage private landowners to assist in species conservation is through the tax code. The federal inheritance tax makes it difficult to maintain ranches intact across generations. Reducing or eliminating this tax would help prevent the subdivision of such ranches into "ranchettes." Wildlife advocates could also encourage counties to give landowners tax breaks for conservation reserves.

Another change that could promote prairie dog habitat would be for states to make prairie dogs a game species. Prairie dog hunting is already such a popular sport in South Dakota that Forest Service officials reduced their prairie dog poisoning program to accommodate demands for more hunting.

For an individual prairie dog, there may seem to be little difference between shooting and poisoning. But for the species as a whole, there is a vast difference. An emphasis on hunting rather than poisoning turns the management goal from prairie dog eradication to sustaining and expanding viable populations of prairie dogs.

Managed sport hunting can benefit ranchers as well as the prairie dog ecosystem. Montana researchers report that controlled shooting in a portion of the Buffalo Gap National Grassland slowed annual prairie dog colony expansion from 15 percent to 3 percent. While this may seem to be a loss for the prairie dogs, they actually benefited because the Forest Service reduced its poisoning program. Researchers also noted that the shooting of prairie dogs generated an estimated $3.2 million of annual income to the local economy.

In addition to hunting revenue, it may be possible for public land managers and private landowners to collect income from other prairie-dog ecosystem recreation. As noted, several species of rare birds use this ecosystem. Fees for wildlife viewing, wildlife photography, and other ecotourism would help promote restoration efforts.


In less than a century, humans reduced the black-footed ferret from a population of millions of animals covering millions of acres to as few as ten individuals on one Wyoming ranch. This near extinction was almost solely due to poorly designed public policies--policies which, for the most part, remain in place today.

The Endangered Species Act was supposed to reverse this policy, but it merely applied band aides that sometimes made the situation worse. At most, government activity has forestalled the extinction of the black-footed ferret. That is quite an achievement given the many threats to the species. However, even that modest achievement is now threatened by agency budget reductions and antagonism to the law from local residents.

For these reasons, new strategies to save the ferret are imperative. These strategies should focus on three areas:

There are no miracle solutions to the predicament of the black-footed ferret. Its current state is the product of more than a century of bad public policy. But the current Congress seems willing to completely reevaluate that policy. Rather than resist such a reevaluation, endangered species advocates should join and promote it to insure that changes in the law will be best for wildlife, the land, and the people for generations to come.

Karl Hess ( has a Ph.D. in ecology and is a senior associate with the Thoreau Institute and a frequent contributor to Different Drummer.

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