Wild Predator Invasion

Can we return apex predators to their natural environments without endangering humans? Airing April 2, 2014 at 9 pm on PBS Aired April 2, 2014 on PBS

Program Description

(Program not available for streaming.) Over the last few centuries we have shot, trapped, and skinned the predators that formerly thrived at the top of the food chain in the wild. Wild bears, wolves, and big cats are all in retreat, and a growing number of scientists are discovering that by eliminating predators, we have changed the environment. Removing predators from the wild has thrown ecosystems off-kilter, triggering domino effects that scientists are just beginning to understand. In "Wild Predator Invasion," NOVA follows scientists who are trying a simple but controversial solution: returning apex predators—like wolves, bears, and panthers—to their natural environments. Can these newly reintroduced predators restore the natural balance of their ecosystems without threatening the humans who live among them?


Wild Predator Invasion

NARRATOR: The suburbs of Naples, Florida: a relaxed and peaceful corner of America, but something is moving into the neighborhood that may shatter that peace: one of nature's most efficient killers, the panther.

MARK LOTZ (Fish and Wildlife Research Institute): It's almost like a perfect storm coming together in areas like where we are right now.

NARRATOR: Predators that were once safe behind bars are now allowed to roam across the state, and the locals are having to get used to it.

AL SANCHEZ: This is learning to live with it. And, you know I, I'm concerned that if they're in an attack mode, I'm going to be his prey.

NARRATOR: Predators are nature's ultimate killers. No other animal threatened them until we came along. We tamed them; we trapped them; we killed them; all to make the world a safer place for us.

Now, scientists are releasing these killers back into the places where we live.

They know it's a project with obvious dangers.

DR. DOUG SMITH (Yellowstone National Park): We know they compete with us. We know they occasionally kill us. You know, we're going to have to work through that, but it's, it's worthwhile.

NARRATOR: So why are they releasing these predators into our backyards? Wild Predator Invasion, right now, on NOVA.

Yellowstone National Park: more than 3,000 square miles of iconic American wilderness. It became a laboratory for testing the idea of bringing back top predators. And here, that predator is the wolf.

Biologist Doug Smith helped devise this ambitious experiment.

DOUG SMITH: I've been interested in wolves since I was a small boy. It's a fascination. It's something that I've truly loved to follow, and so coming to Yellowstone was an opportunity of a lifetime.

NARRATOR: But when he began working in Yellowstone, there were no longer any wolves here.

DOUG SMITH: When the park was established, in 1872, people viewed nature and animals very differently. There was this concept of a good animal, and those were typically the ones we hunted, and then the idea of a bad animal, and they were mostly predators. They competed with us for game, and so when the park was first established, any predator was pretty much fair game.

They shot wolves, they trapped wolves, they poisoned wolves. They used any method they could to get rid of them.

NARRATOR: For them, the wolf was seen as a dangerous menace that needed to be exterminated.

DOUG SMITH: They wanted to civilize the howling wilderness of North America. Well, what made that wilderness howl? It was the wolf. And certainly that was one of their number one objectives, was to rid North America of wolves.

NARRATOR: For 70 years, the park remained wolf-free. And then, in 1995, the scientists decided to bring it back. This was a dangerous and taboo idea, because hatred of the wolf is as old as mankind itself.

Wolves often hunt in packs. They're relentless predators that chase their prey to the point of exhaustion. The reintroduction of the wolf aroused fierce opposition from some who lived and hunted around Yellowstone.

TIM BOWERS (Bear Paw Outfitters): I think it was a good idea to get rid of the wolves when our, our forefathers did, because they're like a bunch of bullies. Get a pack of them together and they're out there just causing trouble and wanting to hurt other animals and that. So, it's kind of like having cancer and then bringing the cancer back, as far as the way I look at it.

NARRATOR: But scientists decided to act because they knew Yellowstone needed help. Behind the picture postcard looks, the northern range of the park was in trouble. And the root cause of it was this animal, the elk. Since the wolf had been eliminated, elk numbers had soared. There were now 10,000 more of them than the park could support.

Herds of hungry elk, sometimes weighing up to 700 pounds, had been gorging themselves on young trees, and the beautiful forest began to disappear.

Roy Renkin is a plant biologist at Yellowstone. He's seen how the elk were destroying the park's ancient legacy.

ROY RENKIN (Yellowstone National Park): A lot of the aspen that we have on the landscape today are probably relics from the last glacial period that we saw here. As the ice retreated and bare ground was left behind, the aspen became established. So, this clone that we're looking at, while the trees may be 125 years old, the organism itself is probably 10,- or 12,000 years old. It's, these are relics from the Ice Age that have been on the landscape for millennia.

NARRATOR: Comparing trees that park rangers have protected with fencing to those left out in the open reveals just how much damage the elk can cause.

ROY RENKIN: This aspen here's about four years old and, and two meters tall. This aspen, out here, is twice its age but only half the height. You can see, obviously, this little guy has been browsed a number of times over a number of years, and it has a lot of forest managers concerned about reversing that trend.

NARRATOR: These two problems: elk numbers spiraling out of control and ancient forests being destroyed, began after all the wolves in Yellowstone had been killed. They were connected to the disappearance of the park's top predator. To understand these changes, Doug Smith drew on a fundamental idea in biology called the "trophic pyramid."

DOUG SMITH: What we call this is the trophic pyramid. And it's a triangle, but it's proportional to the abundance of the life in it. So, at the bottom, we have plants, so that's willow, aspen. And then we have elk and other herbivores. And then, at the top, we have the predators: wolves.

NARRATOR: Predators occupy a small, but important, place at the top of this pyramid of life, and when they are removed, the lower levels of the pyramid explode in numbers.

DOUG SMITH: So, after wolves were taken out, you have this pyramid that essentially didn't have this top level. So, this caused the elk to increase, which caused these plants to decrease.

NARRATOR: Smith believed that if he could bring just a few wolves back to Yellowstone, the animals' power in the trophic pyramid could restore the park to its former glory.

In 1995, 14 wolves were transported from Canada to Yellowstone. They were released where the ecosystem was most damaged, in the northern range.

Seventeen more Canadian wolves arrived the next year.

DOUG SMITH: This landscape, here, was a wolf-less landscape for 70-some years, and so we had pens, four pens from, really, here, that stand of trees, out to where you see those clouds. And we put those wolves in the pens to acclimate them, so they wouldn't try and go back home. We wanted to break the homing response, which we knew they had. And then, we let them go, and we held our breath. We didn't know what was going to happen.

To do this, to bring wolves back to Yellowstone, after such a long absence, in this iconic American park, it, it's hard to describe the excitement.

NARRATOR: But within months of the wolves' return, something unexpected and disturbing began to happen to another animal in the park, the coyote.

DOUG SMITH: Well, right away we saw this was happening. Coyotes were dead. They're not typically eaten, and we picked up many coyotes like this. Unbelievably, there was a 90 percent decline in coyote abundance in the middle of the wolf pack territories. This was, quite frankly, shocking.

NARRATOR: But perhaps it shouldn't have come as a shock, because experience shows that when one part of an ecosystem is changed, the effects can be wildly unpredictable.

The introduction of two animals into Australia stands as a warning from history. Rabbits were brought here and released for hunting, and to provide much needed meat and fur, but there were few predators to control their numbers. So the rabbits were free to breed, and breed, and that led to sheep and other livestock, starving, as millions of rabbits stripped Australia of grass.

Decades later, scientists decided to introduce a new predator to control a plague of beetles, the South American cane toad. It seemed straightforward enough. After all, Australia already had toads of all shapes and sizes. But cane toads are poisonous. Animals unlucky enough to eat them ended up dead. There are now over two-hundred-million cane toads in Australia. They've become a national pest.

Intervening with ecosystems can be a perilous and unpredictable undertaking.

Back at Yellowstone, the newly-released wolves went on the attack. Elk numbers soon started to drop, but scientists needed to answer an important question: were the wolves going to wipe out the elk or help control their numbers?

To find the answer, Smith's team began investigating wolf kill sites.

By examining the marrow within the elk bones, they can find out what sort of animals the wolves are attacking and why.

KIRA CASSIDY-QUIMBY (Yellowstone National Park): We see, especially in the later winter, the marrow is poor on many of the elk that they catch. We also see other problems: tooth abscess, broken legs or other bone problems, and often shows that wolves, if they're looking through a herd, they can see which ones are not quite as healthy as the rest.

NARRATOR: The evidence shows that the wolves were preying on the weak elk and leaving the healthy and strong animals alone.

DOUG SMITH: We feel that there's beneficial effects of that. Certainly that culling makes it a stronger, sometimes smaller, herd, and therefore, there will be enough resources for all the remaining elk to be fit and healthy.

NARRATOR: The wolves were killers but not indiscriminate killers. They had helped to reduce the elk population by 10,000, but also made the herds healthier. But if they were eating the elk, why were they killing but not eating so many coyotes?

The answer to that question would also be found at the kill sites.

DOUG SMITH: Virtually every wolf kill in winter is visited by coyotes. The coyotes couldn't resist this banquet of food, a dead elk that the wolves had killed. And the wolves would kill an elk, they would feed on it, they would gorge on it, they would fill their bellies. And these coyotes would assess the situation, and they would try and come in and take tidbits.

And the problem is many of them visited while the wolves were still there, and wolves started killing them.

NARRATOR: When the wolf disappeared, the coyotes became the top predator. Now, the wolf wanted to show it was the top dog.

DOUG SMITH: You know, I hate to anthropomorphize, but I think I saw fear struck in the hearts of coyotes, because really they were like, "Wow! We thought we were the big dogs. This really is the big dog." And they had problems.

NARRATOR: Wolves were helping to bring elk and coyote numbers down to levels not seen for decades. And the return of the wolf went on to set off a chain reaction that would transform Yellowstone in a way that few could have imagined.

The first signs of change were in the forests.

DOUG SMITH: So, these willows, here, along the creek, when I first came, about 16 years ago, were not like this. They were all browsed down, much shorter. And all these willows, all these stems that you see here, were, were eaten by elk. But since wolves have been reintroduced, we saw it come back before our eyes. And a big factor is, very simply, wolves eat elk. So it's connected.

NARRATOR: The animal and plant worlds at Yellowstone are intimately connected, but this was just the beginning. The wolves ate the elk; the elk stopped eating the willow, and so the forests began returning. But the return of the willow was to help bring a creature back that had almost vanished from the park: the beaver.

Scientists had noticed that few of them remained in the park after the wolves were exterminated, but now, with the willow returning, Smith saw the beavers make a comeback.

DOUG SMITH: The comeback of willow in the park has provided habitat and food for the beavers to make a comeback, and they've increased 12-fold, from one to 12 colonies.

NARRATOR: Beaver dams affect the flow of water. For a small animal, they bring a huge benefit to the park.

DOUG SMITH: When you get a beaver dam, like this, holding the water back, it raises the water table. You can see kind of a meandering stream here that slows the water down. It creates aquatic habitats for more animals and fish, and you get a different community. You lose beavers here, this water races through here. It digs down. You get a straighter channel with less life.

NARRATOR: With fewer elk to eat them and more water for irrigation, the forests were beginning to return. So, instead of bringing death to Yellowstone, as many had feared, the return of wolves had brought life across the park.

DOUG SMITH: The missing piece of the puzzle was the wolf, the top predator. We lost them in the early part of the last century, we gained them late in the century, and 10, 15 years out, we've moved back closer to the point we were about a hundred years ago. This is really exciting stuff.

NARRATOR: The successful reintroduction of wolves at Yellowstone was a powerful demonstration of the ability of a small number of predators to transform a vast wilderness. But other scientists have different and potentially more dangerous plans. They want to release predators much closer to where we live.

This is the city of Naples, in Florida, home to a third of a million people. But not far from these newly built homes lurks one of nature's most efficient killers, the Florida panther. The panther, also known as a cougar, is an ambush predator. It stays hidden until it's ready to strike, then it kills its prey with a bite to the back of the neck, severing the spinal cord.

Before the arrival of the Spanish in the 16th century, it's estimated that more than 1,000 panthers roamed the Florida wilderness, feeding mostly on deer. But over the centuries, as the human population exploded, the predator's hunting territory shrank. By the 1990s, the Florida panther, the state's official animal, was almost extinct; its population less than 30.

Dave Onorato now leads the research team trying to bring it back, in force.

DR. DAVE ONORATO (Fish and Wildlife Research Institute): Florida does definitely identify with the Florida panther. It is really one of the last vestiges of wilderness that we have, really, on the east coast of the United States.

There's very few large predators left in the east, really just the black bear and the panther.

I remember reading about how endangered they were as a kid, and how there were only 20 to 30 left. And, you know, now, actually to be working on trying to preserve them and help them recover, it's, it's, in a sense, you know, been kind of like a dream come true, to be working on that now.

NARRATOR: Scientists like Onorato are trying to save the panther from extinction. If they succeed, the predator could help control some unwanted pests.

Every day, pest controller Al Arcia comes face to face with one of the worst of them, the wild hog.

AL ARCIA (Pest Controller): Right now, it's rooting. That's what it'll do for feeding purposes. They do that on pastures, underneath orange groves, tomato farms, potato farms. They do a lot of damage on a lot of croplands and destroy a lot of pasture for cattle, costing farmers a lot of time and money.

What we're going to try to do now is put this rope around her neck to where I could get her in the trap. You know, they're not afraid of you. They'll charge you. They'll come and get you. They'll bite you, so you have to be careful with them.

We caught one a couple of days ago that was 200 pounds, four-inch cutters. They're what we call dog killers. I mean, you try to catch them with your dogs, they're going to, they're going to hurt you pretty bad.

Let me show you this. This is a hog we caught the other day, in the trap, very aggressive. He charged into the door. You can see his teeth. Those are four inch cutters on them. Those would slice you wide open, just like shaving.

It can be dangerous at times, absolutely.

You know, even though we're trying to control them and take as many out as we possibly can, it's an uphill battle. Can't seem to keep up with it. They're such prolific breeders that we need a helping hand.

NARRATOR: Arcia might get a helping hand from the panthers, if there are enough.

But the panther was in trouble. Within the tiny population, inbreeding was causing genetic defects, making the extinction of Florida's state animal more likely. The species needed genetic diversity to survive. So, in 1995, eight females were brought in from Texas and released into the Florida panthers' habitat, a patchwork of state parks and wildlife refuges just east of the city of Naples.

Since then, panther numbers are rising.

MARK LOTZ: This area is, actually, on one side, abutted by a large interstate. And to the west, we have Naples and the Golden Gate Estates, where wildlife and people start to interact. And there can be negative connotations to that, whether it's a loss of pets, livestock, getting in the garbage. Those are all problems that can occur on that, on the west side of this area here.

NARRATOR: But what's the risk to the public? There are no known cases of a Florida panther attacking a human, but in other parts of the U.S., panthers have, on occasion, attacked people, with deadly results.

Mark Lotz is the member of Onorato's team you call when you've found a panther in your back garden. Recently he's been getting more calls than ever.

MARK LOTZ: The place that we're going to today have had problems in the past with panthers getting their goats. They've had a pig killed just a couple of days ago, so we're just hoping to see if we can find some sign and kind of figure out what we're dealing with here, today.

NARRATOR: Al Sanchez and Reg Malone have lost several animals to a panther that came in the night.

AL SANCHEZ: Apparently, they killed a pig. Heard a commotion, and the pigs are right outside, and when he walked out, there it was. And it was grabbing it and jumped right over the fence. And that's the area right over there.

NARRATOR: A security camera captured an image of a large male panther just before it killed a sheep, dragged it over a fence and buried it.

AL SANCHEZ: You can see the fur on the gate and then the blood over the metal of the fence, as it took it over the fence to the back and dragged it out. I'm like…you know they weigh a good 60, 70 pounds.

REG MALONE: She was an old ewe.

MARK LOTZ: Amazingly strong.

NARRATOR: For Lotz, incidents like this come as no surprise.

MARK LOTZ: As people have encroached on panther habitat, and the panther numbers have increased, it's more common for them to run into each other. You know it's, it's almost like a perfect storm coming together in areas like where we are right now.

NARRATOR: But he hasn't come around to kill or trap the panther.

MARK LOTZ: The example I have is the fences on Alligator Alley.

NARRATOR: So now, the other livestock are protected inside a cage.

AL SANCHEZ: This is what we did so far. It's worked great. With the chain link, we've had to do a little bit of reinforcing every once in a while. We've got the wire that goes all the way through the bottom, we've brought it in about, probably about a foot in, all the way round, in case they try to dig in.

Something did try to jump up, because it ripped the back end of the roof, and it just ripped all the plastic. It took it down, you know?

It used to be we would see it once every year or so, it would come around. Now it's like two weeks. You know, it seems like he's hitting boom, boom, boom, and now I'm starting to panic a little bit when I hear noises.

NARRATOR: Understandably, the most common question for Lotz is this: what do I do if I'm attacked by a panther?

AL SANCHEZ: If I come out here, you know, I, I'm concerned that if they're in an attack mode, I'm going to be his prey.

MARK LOTZ: I don't think you're in a lot of danger there, because people aren't on their menu to eat, but, yeah, when they're on a kill, that's probably the most dangerous, because they're going to want to defend that kill. And the best thing is, you know, don't take your eyes off it, walk backwards.

AL SANCHEZ: I don't know what I would do, if he's turned towards me. That could be…I'm not sure, at that point, if he started walking towards me.

NARRATOR: It may seem surprising, but many people in southern Florida accept panthers as part of the landscape and want them to survive.

AL SANCHEZ: It's just learning to live with it, and it's such a close encounter. You know, it's different than going to a park and seeing it at the park. Now, we know that this is,…

REG MALONE: Big difference.

AL SANCHEZ: …this is the park. You know, we're in the park, so, we'll see.

NARRATOR: Willingness to share territory with predators is a crucial first step in the attempt to bring back a population of endangered panthers.

MARK LOTZ: He's not comfortable up there at all, so, I think, as soon as the dark hits, he's going to come down.

NARRATOR: Nearly every day during winter, an essential but risky procedure takes place.


NARRATOR: Panthers are tracked and tranquillized to allow the team vets to give them a thorough health check.

VETERINARIAN: I'm on the ground.

NARRATOR: It's here that they look for signs of inbreeding.

VETERINARIAN: No kink and no cowlick.

NARRATOR: When the panther population fell below 30, their gene pool became dangerously small. The research team discovered a set of telltale signs of this condition.

DAVE ONORATO: Among these were things like a cowlick of fur on the dorsal side of the panther. So, you can see here the kinked tail of the Florida panther, almost like a corkscrew, here, tail. Usually, in most pumas or panthers this should be just straight, and this probably indicated low levels of genetic variation and inbreeding.

Here you have an individual male that only has one descended testicle. That's obviously going to have an impact on the reproductive viability of the male, but during the early years we would even encounter individuals, from time to time, that had no descended testicles. An extreme case here for a male who ends up being completely sterile and not, basically, contributing anything to the panther population.

NARRATOR: The reason for the inbreeding was simple: there were too few panthers, and they were too close together. The eight Texan panthers, introduced in 1995, brought fresh genes, but for the population to flourish, animals would need to travel to find mates. In other words, panthers would need to roam.

The panthers were fitted with radio collars and that allowed the team to track them across the landscape to see if they were intermingling. But the data showed that something stood in the way, in the middle of southern Florida: I-75, one of America's longest interstate highways.

DAVE ONORATO: Our telemetry data shows how much of a barrier Interstate 75 is to panther movement. You can see here, for instance, all these panther data points from G.P.S. collars and our aerial surveys, how they're stacked up against this interstate highway here, Alligator Alley, or I-75.

NARRATOR: Huge interstates like this were preventing panthers from moving through the landscape and finding new mates to breed with. But the data revealed a hotspot where at least one panther was crossing the lethal highway, near a bridge that spanned a canal.

Hidden cameras revealed that the panther was taking the most dangerous route, crossing the highway itself, instead of walking under the bridge. The research team believed that if they could make this crossing easier, it would encourage other panthers to follow.

DAVE ONORATO: So, what we did is we worked with the Department of Transportation to improve this pathway, here, by laying down this gravel that you can see, to make it more conducive for the panther to use this, as opposed to moving up onto the highway, like he did in those photographs.

NARRATOR: Since adding underpasses with wide trails and making the pathways more comfortable for panthers, signs show the animals are taking advantage and increasing their movement.

DAVE ONORATO: Roadways like this can serve as, like, a barrier to gene flow, and so, in a sense, by allowing a male to move up there, if there's any females that are north of the highway here, he's able to reproduce with them. And that gene flow improves the genetic viability of the population. Any time we can maximize opportunities for gene flow, that's a good thing.

NARRATOR: The Florida panther population is on the rise, now estimated between 100 and 160 cats. And what are all these predators preying upon?

Any evidence that it could help control the unpopular wild hog would be welcomed across the state. To find out, Onorato examines panther feces, or scat.

DAVE ONORATO: This is panther scat, and we find these out on the trail from time to time. They allow us to analyze what they've been eating, and a lot of times, such as with this scat here, you can see that there's small white hairs which are deer hair.

NARRATOR: But the scats also contain a hair that came from no deer.

DAVE ONORATO: These really thick black guard hairs that you can see in this vial here, these are from a wild hog.

NARRATOR: They find that nearly half of the panther's diet is wild hog.

DAVE ONORATO: Panthers in an area will help reduce the number of hogs by using them as a source of prey, so panthers do have a benefit in the ecosystem. Keeping the hog numbers in check is a benefit that panthers provide to the environment.

NARRATOR: The panther's appetite for the much-hated hog may be part of the reason its return has been accepted by many people in Florida. Predators may be dangerous, but they can also be useful.

And what about danger to the panthers? In the last few years, dozens of them have been killed by cars and trucks.

The accidental death of this panther provides an opportunity to investigate whether genetic problems are being solved. Dr. Mark Cunningham is about to perform an autopsy to look for signs of inbreeding.

DR. MARK CUNNINGHAM (Fish and Wildlife Research Institute): We're checking for a kink in the last vertebra of the tail, and this panther is perfectly straight. I don't feel any kink or bend. A lot of times it can be a 180- or even 360-degree kink in the tail, and this one appears to be perfectly normal. And there also does not appear to be a cowlick on the back, here. That's where we usually see it.

NARRATOR: Externally, the panther is fine, but only a dissection will really reveal the animal's genetic health.

MARK CUNNINGHAM: We're able to see some things that we wouldn't be able to assess in the field very well. So, we're able to, to dissect the heart and look for, look for any defects there, specifically atrial septal defects.

NARRATOR: Atrial septal defect, or hole in the heart, is a potentially fatal genetic flaw. Cunningham hopes that their efforts will remove it from the gene pool.

MARK CUNNINGHAM: So we're looking for, for, basically, a hole inside the heart. It should normally be closed, in a healthy normal animal.

Just cutting into the right ventricle here.

NARRATOR: If the atrial septum is intact, it could indicate that the genetic recovery is underway.

MARK CUNNINGHAM: So this is the atrial septum here, and you can see there is no, no hole in the heart, in this cat. This panther has, has none of the congenital problems that we've seen in other, other panthers, so it's definitely is encouraging. It's a good sign for the project.

NARRATOR: The panther, who was born long after the Texas cats were brought to Florida, is genetically sound. This suggests that inbreeding is in decline. But some scientists believe that the panther's gene pool won't be varied enough, unless the animals spread far beyond southern Florida.

DAVE ONORATO: Panthers once roamed from Louisiana all the way through the Deep South: Mississippi, Alabama, Georgia, and then down into Florida. And so, if we're to recover the panther, invariably we have to have more than just one single population, and so it will require the establishment of additional populations, at least, somewhere in the southeastern United States.

NARRATOR: Onorato proposes the creation of protected corridors of wilderness. These will allow the panthers from around Naples to exchange genes with a new population in central Florida, and a further corridor linking to another population of panthers, as far away as Arkansas. It is these kinds of long corridors that have become the most controversial part of the predator release project across the world.

Here in the Alps, another dangerous predator has been brought back from the verge of extinction. It has been given the freedom to roam across hundreds of miles and five international boundaries.

The northern Italian village of Roncona is under attack. A 500-pound brown bear has been rampaging through the streets, terrifying the locals. Dr. Claudio Groff is here to gain control of a chaotic situation.

DR. CLAUDIO GROFF (Fish and Wildlife Research Institute): She entered the village several times, and a couple of times she also tried to enter in houses. And this, of course, worried the people a lot.

NARRATOR: With a large predator attempting to break into houses, the atmosphere in the town is understandably tense.

CLAUDIO GROFF: Ninety-nine percent of the times, it's not dangerous for people, but anyway, of course, in the long-term, we can't accept bears into the villages.

NARRATOR: Fifteen years ago, there were just three old bears in these hills. Today, there is not just one on the loose; 60 bears roam the mountains. Groff has a particular interest in what the bears are doing, as he was part of the team that brought them back.

CLAUDIO GROFF: The bear is part of the identity of the Alps, because since the ancient time he was here, and he shared the caves, thousands and thousands of years ago, with our ancestors, and then the mountains with our fathers, 'til a few years ago. So, it's really part of the Alps culture. It's a symbol of the Alps.

NARRATOR: Starting in the late '90s, Groff and his team released 10 brown bears here. They were imported from neighboring Slovenia, and he hoped that they would form the basis of a new core population in Italy.

CLAUDIO GROFF: We moved all the bears from Slovenia, and then all of them have been released in this small valley, which is called Valle de Tobo.

We released 10 bears, seven females and three males. We started in 1999 and finished in 2002. So, we took four years.

NARRATOR: These bears were then allowed the freedom to roam in the Alps, breed, and, it was hoped, one day reconnect with the original population in Slovenia.

CLAUDIO GROFF: After 2002, we had the first litters, the first production, and the bears started to move.

NARRATOR: It was a proud moment for Groff and his team.

But the bear is not just a predator. It is also a dedicated scavenger, and that means that it is drawn to where we live. Groff now spends much of his time tracking bears like the one that attacked Roncona.

CLAUDIO GROFF: This female bear, called DJ-3, it's a problem bear. Not shy at all, making a lot of damages. And we are trying to see if it's too close to human settlements, to villages mostly.

NARRATOR: A short drive from the town, Groff finds further evidence of a serious bear attack. Fio Malfatti earns his living practicing an ancient Alpine craft: beekeeping. But last night his peace was shattered by one of Groff's bears.

FIO MALFATTI (Beekeeper/Translated): These are the pieces of the old doors. He tried to get inside, but there were bars. When he realized he couldn't get inside, he went onto the roof. He pulled the roof down, pulled the boards up and went in.

NARRATOR: For Malfatti, his ambitions of extending his business are in ruins.

FIO MALFATTI (Translated): For example, I could have bred queen bees down there on my land, but I can't, because the bear wipes everything away.

NARRATOR: The beekeeper doesn't share Groff's romantic ambition. Malfatti was glad to see the bears go extinct and wished Groff had never brought them back.

FIO MALFATTI (Translated): We saw the last of the native bears in 1988. After that, they became extinct, which made me very happy indeed.

Now we are slaves to them.

NARRATOR: While predators may have gained a new lease on life, people have lost freedom to live as they used to. And this tension threatens to destroy the entire predator release scheme.

In 2006, one of Groff's bears, JJ-1, tested this freedom to roam across the Alps. Within weeks, he was in Bavaria, in Germany, the first brown bear to be seen there for 170 years. At first, he was welcomed and given the name Bruno, but as bears travel into new territories, their behavior changes.

CLAUDIO GROFF: When a young male starts to move in a new territory and walk on long distances, he need a kind of easy food, fast food, because it's not in a territory that he knows.

NARRATOR: As a young bear in unfamiliar territory, Bruno began scavenging and killing to stay alive.

CLAUDIO GROFF: So, looking for chicken or rabbits or beehives is the easiest way, and that's what JJ-1 made.

NARRATOR: The reaction in Germany became more hostile.

CLAUDIO GROFF: At the beginning, the German authorities tried to, to capture this bear, but they didn't succeed. And, in the end, they decided it was dangerous for people, so then they decided to shoot it.

NARRATOR: Today, Bruno has a new home, in a museum in Munich, in southern Germany.

For Groff, the shooting of JJ-1 highlighted a flaw in his project. The countries that bordered the Alps needed a common strategy to deal with the bears.

CLAUDIO GROFF: This project has got an importance that is much wider than our small province, at an international level, I would say.

NARRATOR: Back in Italy, in the search for the bear that terrorized Roncona and attacked the beekeeper's business, Groff's team are following a rigid protocol agreed upon by the Alpine countries.

Today, bear dogs are patrolling the foothills. They will chase and frighten the bear away.

CLAUDIO GROFF: They are very aggressive, so they follow the bear, they attack the bear. They even can try to bite the bear sometimes, and the bear usually run away.

NARRATOR: Groff hopes the scare tactics will work. If they don't, he'll need to take more drastic action.

CLAUDIO GROFF: We tried to change her behavior, and if we will succeed, she will be allowed to stay in the mountains. Otherwise, it will be necessary to remove this bear. We hope no, but there is a chance.

NARRATOR: Groff must confirm the bear is far enough away from the village. Since it's tagged with a radio collar, they can locate it using transponders.

CLAUDIO GROFF: Okay, I think that here we can get the signal, because she must be pretty close.

NARRATOR: Her location, high up in the hills, suggests she's preparing for hibernation.

CLAUDIO GROFF: Winter is coming, you know. Snow is already arrived. And she will spend around four months in there. And for this year, probably, we will have no more problems. We will see next spring what will happen.

NARRATOR: Roncona is out of danger, at least until winter is over.

It's become clear that if predators are to be given the freedom to roam across hundreds of miles, the scientists responsible will have to be close behind, to keep us and them, safe.

Back in Yellowstone, the wolves have spent about two decades in this wilderness. No human has been killed or hurt, and the ecosystem continues to flourish.

DOUG SMITH: Wolf recovery to Yellowstone National Park is an example to the world. Ecologically, it's a different place, a good one. There's so much negative nowadays. Here's a positive message.

NARRATOR: Smith believes that, quite simply, we need predators.

DOUG SMITH: We know they compete with us, we know they occasionally kill us. You know, we're going to have to work through that, but it's, it's worthwhile. And if we're going to restore wild nature, if we're going to preserve it, these apex predators have a key part in that.

NARRATOR: Together, the work of these different scientists forms part of a radical new vision of conservation biology called "rewilding."

The release of wolves has revealed how just a few carnivores can radically transform an ecosystem. The release of panthers has tested how new core populations of predators can survive and grow. And the reintroduction of bears into the Alps has shown how corridors might be created for them to roam freely.

The ultimate ambition of rewilding is to restore and recreate the great wildernesses of our planet, harnessing the power of predators to control the natural world in a way that we cannot.

Broadcast Credits

Nick Clarke Powell
Gerard Evans
Rob Tinworth
Rob Goldie
Ted Marcoux
Steven Bowden
Danny Finn
Paula Robert
Laura Davey
Marie O'Donnell
Emma Chapman
Evi Efue
Kirsty Leishman
Alex Leask
Michael H. Amundson
Peter Lynch
Michael H. Amundson
Maggie Oakley
Sarah Conner
Lizzie Crouch
AP Archive
Florida Fish and Wildlife Conservation Commission
Forest and Wildlife Service of the Provincia Autonoma Di Trento, Italy
Getty Images
Photolibrary/Oxford Scientific (Ofs)
ProSiebensat.1 TVD GmbH
State Archives of Florida
Thought Equity Motion/National Geographic
Wolfgang Wiggars
Tampa's Lowry Park Zoo
yU + co.
Walter Werzowa
John Luker
Musikvergnuegen, Inc.
Ray Loring
Rob Morsberger
The Caption Center
Spencer Gentry
Jennifer Welsh
Eileen Campion
Eddie Ward
Kate Becker
Kristen Sommerhalter
Linda Callahan
Sarah Erlandson
Scott Kardel, Esq.
Janice Flood
Susan Rosen
Rachel Connolly
Kristine Allington
Tim De Chant
Lauren Aguirre
Lisa Leombruni
Ariam McCrary
Brittany Flynn
Rebecca Nieto
Nathan Gunner
Linzy Emery
Elizabeth Benjes
David Condon
Pamela Rosenstein
Laurie Cahalane
Evan Hadingham
Julia Cort
Chris Schmidt
Melanie Wallace
Alan Ritsko
Paula S. Apsell

Produced for NOVA by BBC

© 2011 BBC

Wild Predator Invasion Additional Material © 2014 WGBH Educational Foundation
All rights reserved

This program was produced by WGBH, which is solely responsible for its content.


(Florida panther)
© Purestock/Getty Images


Al Arcia
Pest Controller
Tim Bowers
Bear Paw Outfitters
Kira Cassidy-Quimby
Yellowstone National Park
Mark Cunningham
Fish and Wildlife Research Institute
Claudio Groff
Fish and Wildlife Research Institute
Mark Lotz
Fish and Wildlife Research Institute
Dave Onorato
Fish and Wildlife Research Institute
Roy Renkin
Yellowstone National Park
Doug Smith
Yellowstone Wolf Project

Preview | 00:52

Full Program

Full program available for streaming through

Watch Online
Full program available