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Saving The Native Prairie — One Black-Footed Ferret At A Time

A black-footed ferret on the alert in South Dakota's Conata basin.
Courtesy of Dean Biggins
A black-footed ferret on the alert in South Dakota's Conata basin.

American pioneers saw the endless stretches of grassland of the Great Plains as a place to produce grain and beef for a growing country. But one casualty was the native prairie ecosystem and animals that thrived only there.

Some biologists are trying to save the prairies and they've picked a hero to help them: the black-footed ferret. In trying to save this long skinny predator with a raccoon-like mask, the biologists believe they have a chance to right a wrong that nearly wiped a species off the planet.

Ferrets, it turns out, suffered collateral damage in the century-long campaign by human farmers and ranchers against the prairie dog. Prairie dogs compete with livestock for forage, and riddle and ruin crops with their tunnels and burrows.

But prairie dogs are also key prey for the black-footed ferret, a member the weasel family. Killing off prairie dogs with poisons has put pressure on ferret populations, too.

Eventually, the native ferret was almost extinct, says Forest Service biologist Randy Griebel. "It was literally down to just a handful of individuals," he says.

These days, as many as several hundred wild ferrets are scattered across the grassland and prairie from Arizona to Canada. But it takes a tremendous amount of work to keep these animals on the landscape because of a variety of foes — chief among them a potent microbial killer, plague.

At 11 p.m. one night this fall, Griebel headed out for his second shift of the day – spotlighting for ferrets in South Dakota's Conata Basin. The idea is to locate every ferret in Buffalo Gap National Grassland, give it a checkup and vaccinate it against plague, a bacterial disease that threatens the ferret's comeback.

Griebel drives off-road over a vast stretch of grassland. He uses his right hand to direct a beam of light across the landscape from a spotlight mounted on the top of his truck.

"All right, so what we're looking for is really super bright, emerald green eye-shine," says Griebel, whose compact, muscular build and short haircut betray his first career, in the U.S. Army.

The ground is pockmarked with bare mounds of earth; each one is the entrance to a prairie dog burrow.

Ferrets are wily. They hunt at night — sneaking up on prairie dogs asleep in the burrows, and biting their throats. Ferrets live in the burrows, too.

Forest Service biologist Randy Griebel catches a black-footed ferret after a night of searching.
Elizabeth Shogren / NPR
Forest Service biologist Randy Griebel catches a black-footed ferret after a night of searching.

Ferrets spend most of their time underground, day and night, so it's hard to find them. Hours pass and Griebel has not seen any flashes of green from ferret eyes.

"We're just going to drive this race track over and over and over," he says. In the long hours of looking for ferrets, Griebel's mind plays tricks on him.

"Sometimes it's a ferret; sometimes it's just a bug faking me out," he says with a laugh. "Then, about 4 in the morning, you'll start hallucinating. You'll be seeing green eye-shine all over the place."

Biologists keep up this nightly ritual throughout the fall. It might seem like an absurd amount of work, just to benefit a relative of the weasel, but Griebel says he's driven by the fact that his own species nearly annihilated ferrets by poisoning their prey.

The difficulty of the goal drives him all the more. The ferret went through so much, Griebel says. "Now we're going through so much to try to bring it back."

Ranch Dog Turns Up Wild, Native Ferrets

The roller coaster ride to save the black-footed ferret has lasted more than 30 years, and Dean Biggins, a biologist for the US Geological Survey, has been there from the beginning.

As he drives through ferret habitat in South Dakota's Badland's National Park, Biggins recalls the elation he felt in 1981, when he learned that a remnant population of native ferrets, thought by many to be extinct, had been discovered by a ranch dog in Wyoming.

Biggins says he remembers feeling, "Boy, this is really something! I'll actually get to see one of these animals, [and not just] a mounted specimen."

But a few years later, that lone population started dying fast. So, biologists trapped every last one — 18 in all.

That was a turning point. Government biologists created a successful captive breeding program, and within a few years started putting captive-born ferrets back into the wild.

At first, it didn't go well. The ferrets were so unused to facing predators that coyotes, owls and other hungry animals gobbled them up.

"We just couldn't keep them alive," Biggens recalls. Researchers figured out they needed to give young captive ferrets more training before releasing them to the wild. Keepers started putting captive ferrets in outdoor pens with burrows in them. The young ferrets learned to hide at any sign of danger.

Plague Hinders Ferret Comeback

But it's been much harder to protect ferrets from plague.

In 2008, the Conata Basin had the most ferrets in the country — 350. But Griebel began to notice, as he made his rounds, that he wasn't seeing ferrets in many of the spots where he always used to find them.

Soon, it became clear that the ferrets' main prey was disappearing, too. Prairie dogs started dying by the hundreds of thousands from a fast-moving infection that turned out to be plague. Researchers were caught by surprise because plague had never been in South Dakota before.

The bacteria that cause plague are carried by fleas. Ferrets had to be catching plague either from flea bites, the scientists surmised, or from eating plague-infected animals that had been bitten by fleas.

It's taken a Herculean effort to save the 70 or so ferrets that are left here. Griebel assembled a crew of workers on ATVs who squirted insecticide dust into every prairie dog burrow they could find — hundreds of thousands of them.

Prairie dogs are ferrets' chief prey. The two species often share tunnels — and plague-infested fleas.
/ Courtesy of Dean Biggins
Courtesy of Dean Biggins
Prairie dogs are ferrets' chief prey. The two species often share tunnels — and plague-infested fleas.

The crew still works for 5 months every year, spraying and respraying every burrow across the vast grasslands. Still, on the long nights he spends searching for ferrets in the fall, Griebel feels anxious when he doesn't see that telltale emerald eye-shine.

Green Glow After Midnight

At 2:30 a.m., Griebel spins his truck around for another lap and finally spots a flash of emerald green.

The U.S. government regularly sprays hundreds of thousands of prairie dog burrows in South Dakota to keep plague in check.
Elizabeth Shogren / NPR
The U.S. government regularly sprays hundreds of thousands of prairie dog burrows in South Dakota to keep plague in check.

"I see you buddy," he says, speeding toward the glow.

Illuminated by his spotlight and a full moon, Griebel quietly sets a trap, and then gets back into the truck.

He returns every hour, but each time the trap is empty. In the remaining hours before dawn, he sees no more flashes of green.

As the sun rises, Griebel checks his traps one last time. Success.

"We got him!" Griebel calls. "Did you see him?' That is so awesome!"

Capture, Treat and Release

The ferret sounds an ear-splitting alarm as Griebel puts it into a small crate.

He takes the animal for a checkup in a camping trailer that's parked a short drive away, in a sea of grass.

Biologist Travis Livieri, the executive director of Prairie Wildlife Research, a nonprofit conservation research group, gets to work inside the trailer. He can tell from a microchip in the animal that this female ferret was born last year.

He notices that the ferret has lactated, which means she's given birth — good news. Plague hit male ferrets particularly hard last year, and many females didn't have litters.

Livieri gives the animal vaccines for distemper and plague, and combs her to see if she has fleas. She doesn't.

Livieri believes the fate of ferrets will continue to hinge on human ingenuity and science.

Better vaccines, he hopes, will be developed to keep ferrets and prairie dogs safe from plague.

Livieri first started following this population of ferrets 18 years ago, and was surprised by how quickly he fell for the prairie. It's a majestic place, he says, and quintessentially American. Bringing back a species that's only found here is worth whatever effort it takes.

"You look into those little eyes and they look back at you. You see something. You want to help right that wrong."

Randy Griebel releases the female ferret near the prairie dog burrow where he caught her a couple hours earlier. He'd worked an entire night for just one animal.

"Anytime you work this hard, good things should happen," Griebel says.

Sure enough, a few weeks later, he catches the same ferret again. This time, she has with her at least two offspring.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Elizabeth Shogren is an NPR News Science Desk correspondent focused on covering environment and energy issues and news.
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