Wild Ways

PBS Airdate: April 20, 2016

NARRATOR: Lions, elephants, bison, wolves: all over the world, their numbers are plunging, but why aren't parks, like Yellowstone, and wildlife preserves worldwide enough to save these magnificent creatures?

HARVEY LOCKE (Yellowstone to Yukon Conservation Initiative): As big as Yellowstone is, it's not big enough on its own.

NARRATOR: These sanctuaries are fast becoming islands in a sea of human development…

HARVEY LOCKE: And the first to go are the large mammals.

NARRATOR: …with roads and highways cutting them in half.

STEPHEN WOODLEY (Parks Canada): If you chop an ecosystem up, it's immediately in trouble.

NARRATOR: No longer can elephants migrate, as they have for thousands of years. Gone are the vast expanses lions need to roam and interbreed, to keep their prides healthy.

CRAIG PACKER (Serengeti Lion Project): The females are mating with males who are their cousins or even their fathers.

NARRATOR: Now scientists are racing to save them…

MICHAEL CHASE (Elephants Without Borders): We know, with pinpoint precision, where the elephant is 24/7, tracking their movements, understanding their needs.

It's a way of them communicating which areas they need, to move across this vast landscape.

NARRATOR: …reconnecting parks and preserves…

DAVID QUAMMEN (Nature and Science Author): To allow our animals to move from one patch of protected landscape into another.

NARRATOR: …making the most of the wilderness that remains.

MICHAEL SOULÉ (Society for Conservation Biology): It's our last chance to protect the diversity of life on Earth.

NARRATOR: Wild Ways, right now, on NOVA.

Tanzania, East Africa: Serengeti National Park, home of the greatest wildlife spectacle left on Earth.

This is the "great migration," 2,000,000 wildebeest, zebra and gazelle follow annual rains, along ancient pathways, across Tanzania and Kenya. Sheltered by national parks and game reserves covering 12,000 square miles, some species are still being lost.

Rhinoceros have been hunted out by poachers for their horns. Wildebeest and zebra are at risk, because their dry-season water supply has been diverted for human use. A controversial road and rail project threatens to sever the ancient migration route.

And Serengeti is not alone. All over the world, wild animals are at risk. In the United States, Yellowstone is one of our largest national parks. With nearly 3,500 square miles, it's bigger than some countries. Millions come here each year to see its wildlife and natural wonders, but this park, like many around the world, may not be doing its job.

STEPHEN WOODLEY: We have set up protected area systems in all parts of the globe. Most of them are too small to protect the native biodiversity that they're set up to protect.

NARRATOR: So, what will it take to protect these animals, especially when they leave sheltered areas to forage for food and find mates? This places them in danger, because even the best parks have become islands of nature surrounded by human development.

To find a solution, biologists are following animals along their ancient migration routes. By understanding their patterns and needs, scientists hope to come up with a new approach to save wild species all over the world.

One key question is how much land wild animals need to survive. Back in the Serengeti, the African lion stalks the great migration. Lions survive by preying on the herds of wildebeest and zebra. Biologist Craig Packer has been studying Serengeti lions for decades.

CRAIG PACKER: The Serengeti Lion Project is one of the longest continuing studies of any animal species on Earth. We currently keep track of about 24 prides of lions. That's about 300 individuals, but since the study began in 1966, after 50 years, we have records of nearly 5,000 individuals.

Here's the female that walked off first. She has these three spots.

NARRATOR: Packer knows every lion in his study area, who they mate with, and how many cubs they raise. It's a unique natural history, going back many generations.

CRAIG PACKER: So, lions live in very distinctive groups, called prides, which consist of a stable core of females that live in the same general area, generation after generation.

NARRATOR: About a dozen lions live communally in a pride. Females will even nurse each other's cubs. Male lions come and go, mating with females from different prides. This promotes a healthy exchange of genes, but if a park is too small and isolated, this interbreeding can't take place, and the lions will be at risk.

Serengeti, about the size of Connecticut, is large enough to support 70 lion prides. Just to the southeast is Ngorongoro Crater, which is a very different situation. Ngorongoro features a protected area in a volcanic crater.

The crater rim encloses a wildlife sanctuary, but it's surrounded on all sides by Masai villages. The Masai survive by herding cattle. To defend their herds, or for prestige, they will kill lions who would enter or leave the volcano. This means the Ngorongoro lions are isolated, and that leads to inbreeding.

CRAIG PACKER: So, if you have a population that's as small as the Ngorongoro Crater, there's only about 30 adults, so the females are mating with their cousins or their nephews or even their fathers, in some cases. Here's where you risk inbreeding depression. And in inbreeding depression, you get cubs that are smaller. They might not live to their first birthday, and they are much more susceptible to disease.

NARRATOR: In addition, small populations are more vulnerable to drought, famine and over-hunting. Studying lion populations all over Africa, Packer has arrived at the minimum number of lions needed for a group to survive.

CRAIG PACKER: Lions, like any mammalian species, need to live in a fairly large population in order to maintain its genetic health. And studies of these situations suggest they need to have at least a thousand breeding individuals in a population, to maintain proper levels of genetic diversity.

NARRATOR: When an isolated population is wiped out, and there are no lions close by to resettle the area, that species is extirpated, gone forever from that location.

Once, over a million lions roamed and interbred, from Great Britain to South Africa. Today there are fewer than 25,000 left, most living in a handful of protected areas. Only four preserves have the thousand lions necessary for long-term survival.

Parks around the world face a similar problem, as human development encroaches.

STEPHEN WOODLEY: If you chop an ecosystem up, it's immediately in trouble. And it will lose biodiversity, guaranteed. We know this as much as we know anything in conservation biology.

NARRATOR: The loss of biodiversity can be seen on every continent. Large predators, like lions, have declined by 99 percent. Tigers have fewer than 3,000 survivors. Grizzlies, mountain lions and wolves followed a similar drastic decline in North America, where bison plummeted from more than 30- million to a few hundred.

These large mammals are the first to go when a park is too small and isolated. In North America, the grizzly bear is a prime example. Grizzlies used to inhabit most of western North America, but as human populations grew, bears were confined to ever-shrinking pieces of land. About 40 isolated bear populations lasted into the 1920s. Now, outside Alaska, there are only two viable large groups in the U. S., in and around Glacier and Yellowstone National Parks.

Yellowstone was the world's first National Park, founded in 1872. At that time, it was part of a wilderness that stretched from Mexico to the Canadian Arctic, but now it's surrounded by ranches, towns and highways. And that's a problem for species like grizzly bears that need room to roam.

Grizzly bears are true omnivores, eating everything from berries to meat. They dig for roots and tubers, but will also consume fish, greens or insects. To make it through their winter hibernation, they must put on 1/3 of their body weight in summer and fall. In their search for food or mates, it's inevitable that some bears will wander out of Yellowstone.

Biologist Mike Proctor wants to understand the bears' habits so they can be better protected.

MICHAEL PROCTOR (Trans-border Grizzly Bear Project): The canines are in very good shape. The incisors have medium wear. They're still pretty good incisors, so it's not an old bear. The molars are medium worn, so we're looking at a six- to eight-year-old male.

NARRATOR: Proctor darts and tranquilizes grizzly bears to monitor their health.

MICHAEL PROCTOR: I'm going to do a physical exam, just see any injuries or what shape he's in. He's got a little wound there. Why don't you write down "a wound?" Looks like a fight with another male. "Right side of his cheek, puncture wound."

When we first get a bear immobilized, we go in and make sure it's breathing correctly, and do a round of vitals, so we understand its heart rate, oxygen concentration, its temperature. We measure its weight. That's very important. Its age. We look at parasites and ticks and body condition, in general. We take blood. We take a D.N.A. sample, hand pulled. Of course it's on a sleeping bear.

The heartrate's 60; good thing I checked.

NARRATOR: Then he attaches a radio collar that will track the bear's movements using G.P.S.

MICHAEL PROCTOR: After you put a radio collar on a grizzly bear, it collects G.P.S. locations every hour for two years. That collar follows the bear and goes everywhere it goes, and then you put that on 40 or 50 or 60 bears, and you really start to understand the patterns of how bears use landscapes, how they move, how they use habitat, and what is important to them.

This is the electronic drop-off, so the bear doesn't wear this the rest of his life. They work pretty good.

I'm going to watch the head, pretty clear here. His nose is twitching. Hey, we're done. We've got an arm movement. Pack up.

NARRATOR: The radio collars tell an amazingly detailed life story of grizzly bears: where they find food, make their dens and choose mates. After two years with his mother, a male cub moves out of her territory. But female cubs will settle nearby. Males will travel widely, competing with other males for mating rights to several females.

For example, Proctor tracked one male, as he moved several hundred miles from Canada, across Idaho, and on into Washington, when his collar released.

The challenge is that only 25 percent of grizzlies are breeding-age females. If a group becomes too small, there won't be enough females, and that's the end of the line for that population. Proctor decided to use D.N.A. evidence to pinpoint where that's happening.

Bears have favorite trees they use for a good back scratch. Proctor realized he could use the fur they leave behind to test the bear's D.N.A. Then he developed an even better method to sample a lot more bears.

MICHAEL PROCTOR: I'm wrapping a kitchen-sized barbwire corral, which I'm going to fill with very smelly bait, to lure in a grizzly bear. That grizzly bear is going to come in here to smell that bait, and leave some hair on this wire. And with that hair, he doesn't even know he's being sampled, we'll use it for our answer to conservationists' questions using D.N.A. fingerprints.

NARRATOR: D.N.A., collected from the skin follicles at the base of each hair, contains the genetic code unique to each individual. And this can reveal whether different groups of bears are related and whether they've been interbreeding.

MICHAEL PROCTOR: We were looking for places where grizzly bears were not interbreeding for some reason or other, and we found many of those places across the landscape. They all correlated with major highways and settled valleys.

NARRATOR: Where highways and human settlements make it hard for bears to move around and interbreed, Proctor discovered that grizzlies are becoming separated into genetically different groups. His D.N.A. records identify 17 populations from Yellowstone Park to the Arctic Circle.

In the Arctic, bears move freely and interbreed. Traveling south, toward the U.S.-Canada border, isolation gets worse. The 700 bears of Yellowstone are completely cut off, almost as if they were living on an island. And scientists now understand why that is a threat to many species.

In fact, the first clues that parks may be in trouble came from studying islands. Starting with Charles Darwin's voyage to the Galapagos in the 1830s, a new field of biology developed, known as "island biogeography."

DAVID QUAMMEN: Island biogeography is a really important field of study for conservation, for the prevention of extinctions. It's the study of where creatures live, where they don't live, and why: "bio," "geography." Island biogeography is that field of study applied to islands, but, importantly, also to island-like fragments of habitat.

NARRATOR: Islands often are home to unique species, like the Galapagos iguana and the giant tortoise. But islands have very limited resources. The smaller the island, the fewer species it can support.

To see how this principle applied to national parks, which are like islands within the larger continent, biologist Michael Soulé and his students launched a series of studies. They wanted to know how well national parks were doing at protecting the species that were there when the parks were created.

MICHAEL SOULÉ: After doing this, this analysis of what remained in the national parks, in the United States, was completely consistent with the principles of island biogeography. The bigger parks retain almost all of their species, but only the biggest parks still had grizzly bears and wolves and mountain lions. The smaller the park, the fewer the predators there were, and the fewer the species there were overall.

NARRATOR: These studies became the foundation for the new field of conservation biology. Michael Soulé discovered that a small park also has another challenge for species survival, the balance between males and females.

MICHAEL SOULÉ: Small size is bad for creatures, genetically and also demographically, because, for example, if there's only five or six mountain lions in a park and they can't get in, they can't get out, every few generations all those five or six will be males, and that's the end of them, because they can't reproduce: they're all males.

NARRATOR: No longer allowed in national parks, hunting has had a huge impact on animal populations. Considered pests, wolves were completely hunted out of Yellowstone in the 1920s.

Today, Doug Smith directs the Yellowstone Wolf Project, created to bring wolves back into the park.

Smith and the Yellowstone Wolf Project collar and track the newly returned wolf packs. Reintroduced in 1995, they now occupy every part of the park. Wolves were brought back into Yellowstone, because biologists realized that, without them, the entire ecosystem was starting to unravel. In 75 years without wolves, Yellowstone's elk population had surged and was destroying the important river-bottom ecosystems.

DOUG SMITH (Yellowstone Wolf Project): Willow plains, like this, were rare and eaten down. When I first came to Yellowstone, in 1994, stands like this were down to my knee level, as every stem was clipped off by an elk, I mean every stem.

NARRATOR: Without the willows, many birds disappeared. Without willows shading the streams, water temperatures rose and fish populations declined. Beavers declined as well, and without their constant maintenance of wetlands, erosion grew worse. But when wolves were reintroduced in 1995, and started hunting elk, the river-bottom willows recovered.

DOUG SMITH: This growth in structure has produced bird habitat. We're getting birds, like willow flycatchers and Wilson warblers, that we have not had before. We had an increase in beavers. This very willow plain, here, I am surveying, it has, depending upon the year, four to six beaver colonies, right back through this. They increased 12-fold after this willow resurgence.

NARRATOR: Biologists believe the ecosystem is recovering, but the question is whether Yellowstone's wolves can survive, if they can't reach other wolf groups to interbreed.

DOUG SMITH: Well, wolves are going to have to be connected to other wolves. I mean, through time, that has been shown to be the saving grace for a population of animals. We need that connectivity. We can't just do it with this island called the "Greater Yellowstone Ecosystem."

NARRATOR: If animals can't come and go, the parks we are counting on to save wildlife are in trouble, but biologists have a solution.

MICHAEL SOULÉ: Conservation biologists have known how to end the extinction crisis, to protect thousands of species in the United States and other parts of the world, by simply restoring the connections between the wild places that still persist.

NARRATOR: It's known as "connectivity conservation," linking the last places where wild animals survive makes the most out of those core habitats that remain. But which places outside of parks are the most important to protect?

To find out, scientists like Mike Proctor, follow the animals.

MICHAEL PROCTOR: One of our first bears we caught crossed the highway about 12 times in one summer, exactly in the same spot. And that taught us there was something very important happening at that particular site. The next year, when I came back to work, actually there was a for-sale sign, right at the spot where this bear crossed the highway 12 times. And I just went, "Okay." A lightbulb went off in my head: "there's something important here, and we have to act."

NARRATOR: Mike Proctor worked with conservationist Harvey Locke, to find a way to protect the bears' crossing place.

HARVEY LOCKE: Research by the Trans-border Grizzly Bear Project showed that this sad little parcel of land, over my shoulder, turned out to be the key connector for the mother lode of grizzly bears, located in the wild Purcell Mountains in southern Canada, across this highway, south, into the States, to the recovering population of grizzly bears in the Cabinet-Yaak area of northern Montana.

NARRATOR: Protecting this landscape connection has enabled bears to move south from Canada's Purcell Mountains and connect with grizzly populations in Montana and Idaho, which are too small to survive over time. This linkage, called the Kidd Creek Corridor, is one piece of a much larger vision.

HARVEY LOCKE: When it became clear, through conservation biology, that these wonderful national parks like Yellowstone and Banff, as great as they were, weren't sufficient unto themselves, that they needed to be connected to each other, we came up with this idea called the "Yellowstone to Yukon Conservation Initiative." The idea is to make a great corridor from Yellowstone, up the Rocky Mountains, all the way into northern Canada, near the Arctic Circle.

NARRATOR: Yellowstone to Yukon is an ambitious plan to link national parks. These core areas are safe havens, where animals can find food, breed and live without being threatened. Connecting them would recreate the large landscape that existed before humans came.

HARVEY LOCKE: Now, we know that, as big as Yellowstone is, it's not big enough on its own. Islands in a landscape become islands of extinction, and the first things to go are the large mammals. The large mammals, the ones that are at the greatest risk of disappearing in the 21st century, the big things, like bison and grizzly bears, require us to practice conservation at an enormous scale.

NARRATOR: The plan is to create a 2,000-mile corridor, linking Yellowstone to the wilderness areas of central Idaho. This would connect to Glacier National Park and Waterton Lakes Park, across the U.S.-Canada Border and on to Banff, Canada's premier national park. Farther north, protected areas become bigger and wilder, all the way to the Peel Watershed, in the Yukon Territory.

The point is not to take over private land along this corridor, but to work with landowners and managers of public lands, like national forests, so that wildlife can safely move through.

Proctor's D.N.A. map has identified the private lands most critical to landscape connections. One of these, in British Columbia, is known as the Duck Lake Corridor.

HARVEY LOCKE: Typically, in our part of the world, the mountains are in public hands, and the valley bottoms are in private hands. This Duck Lake Corridor is a classic example.

NARRATOR: Grizzly bears live in the mountains, but they need to cross private lands in the valley to find mates and forage for food. Conservationists have purchased some of this land, but also work with landowners to find ways to protect animals passing through.

They encourage farmers to fence in orchards, since bears will go after berries and other fruit. They also recommend bear-proof containers for securing garbage. Specially designed bins can help keep bears away from human settlements and farms, where they may wind up getting shot.

Clearing the way for bears can help protect other species, too. For example, biologists learned that the Duck Lake area is critical for the seasonal migration of northern leopard frogs.

HARVEY LOCKE: We know that this mosaic of habitats, from farmer's field, to wildlife sanctuary, to pieces of public land, is the critical corridor for grizzly bears. And we also know that, if we can protect the movements of grizzly bears, that we're going to catch something like the needs of 85 percent of the other species in the system.

NARRATOR: Grizzlies are an "indicator" species, a way to gauge the health of not just one species, but an entire ecosystem.

Another major barrier to wildlife is the four-lane highway. With several lanes of traffic and speeding cars and trucks, these roads can be death traps. Many animals are not as lucky as this cub. Millions are killed every year.

Two major four-lanes cut across Yellowstone to Yukon: Interstate 90, in Montana and Idaho, and The Trans-Canada Highway, which runs right through an important core area, Banff National Park.

STEPHEN WOODLEY: Banff is Canada's iconic national park, and it's split by a major transportation corridor. And, as the traffic volume went up, in the Trans-Canada, it fractured the park into two sections. Large numbers of elk and grizzly bears and black bears and coyotes were getting killed every year, and it was very dangerous for people.

NARRATOR: Woodley and other scientists at Parks Canada helped design a road that would protect both humans and animals. Forty-four crossing structures now allow wildlife to move safely though Banff National Park.

STEPHEN WOODLEY: There's two basic kinds of crossing structures. There's the underpasses, which are dark tunnels, and then there's these large overpasses. When you're on top of them, even when you have a four-lane highway running underneath you, it seems like you're in the forest. There's trees growing on them.

And it seems like certain kinds of animals, like grizzly bears and wolves, like to use those structures.

NARRATOR: Motion-activated cameras have documented more than 200,000 wildlife crossings, and the number of animal deaths has been reduced.

South of the U. S.-Canada border is the Flathead Indian Reservation, a key crossing point for animals moving between Glacier National Park and the Church wilderness area, in Idaho. But Route 93 runs right through the reservation.

When it came time to repair the highway, tribal elders insisted on a design that would be safe for animals and people as well. Today, 43 crossing structures complete one of the most wildlife friendly road projects in the world.

Whisper Camel-Means is a wildlife biologist for the Salish and Kootenai tribes. She maintains a network of motion-sensor cameras to document animals using the crossing points.

WHISPER CAMEL-MEANS (Salish and Kootenai Tribes): The crossing structures are being used. We're pretty impressed with the number of animals that are using them. There's this whole new concept of road ecology, where people are actually thinking about how roads affect the ground, and affect natural resources and affect all of us.

NARRATOR: Unlike the Trans-Canada Highway in Banff National Park, Route 93 runs through ranches and towns. Local residents had to be convinced that the crossing structures were worth the expense.

WHISPER CAMEL-MEANS: The cost of building these crossing structures and putting this kind of mitigation into a road project is less than the cost of a bunch of people hitting animals, a bunch of people getting into wrecks, people losing their lives. They're not that expensive when you look at the big picture.

NARRATOR: This project allows animals to safely move to and from the large wilderness areas of Central Idaho. But between there and Yellowstone, in Wyoming, the area is filled with cattle and sheep ranches.

The Centennial Valley is a piece of the Old West, featuring large ranches that stretch as far as the eye can see. Jim Roscoe is a wildlife biologist who works with ranchers to help wildlife safely pass through their land.

JIM ROSCOE (Centennial Valley Association): If there's any one thing that might have a pretty substantial impact for animals being able to move, but isn't a huge change in somebody's management or extremely costly, it might be in dealing with wildlife-unfriendly fences.

NARRATOR: Outdated fencing poses real obstacles to animal movement.

JIM ROSCOE: It's a woven wire that has all these little squares. These things become buried in the ground and are a significant barrier to anything that's trying to move through here. The worst of it is whether it's young deer, young antelope, young elk, young moose, they have a really difficult time dealing with this.

NARRATOR: Even fully-grown antelope struggle with these old sheep fences. Built for speed, they can't jump very high. They need a fence design they can duck under.

JIM ROSCOE: These are the kind of fences that we're looking at across the landscape, that we're trying to modify or replace or remove where we can, because there's other fence designs that can be as effective now and removes this total barrier to wildlife. The other thing you can do, certainly, is just leave the gates open when the livestock aren't in the pasture.

NARRATOR: But the most contentious issue around Yellowstone is what to do about wolves, since they were re-introduced here in the 1990s. The problem occurs when wolves wander beyond park boundaries. Martin Davis is a rancher in Paradise Valley, just north of Yellowstone Park.

MARTIN DAVIS (Paradise Valley Rancher): I wish wolves weren't here. It's just one more thing we have to worry about. We have to go to the mountains and check on the cows every other day now, when back in the day, before wolves, we were able to check on them just once a week or so.

When the wolves are bothering the cows, then we've found our weaning weights are down, pregnancy rates down, so it's been quite an adjustment over the last 15 years or so.

NARRATOR: Some ranchers take a harder line on wolves. State laws permit them to shoot wolves on sight. Hunters are also angry at the spread of wolves, which they say impacts the elk hunt. States surrounding Yellowstone have opened wolf-hunting seasons. Many of the collared wolves scientists track have been killed when they leave the protection of the park.

Wild bison are also targeted, as some ranchers worry that they might spread disease to cattle. It's these kinds of issues that have to be resolved before national parks can be fully connected.

DAVID QUAMMEN: The vision of connecting Yellowstone to the Yukon, reestablishing links among those major patches of wild landscape, it is hugely ambitious; it is not impossible. It will take a lot of really patient, pragmatic, cooperative work on the ground, with all these different people who live and make their living on these landscapes, between these wild places.

NARRATOR: In the far north, where there are fewer people and many animals, some core wildlife areas are gaining ground. In Canada's Northwest Territory, an area the size of Switzerland has been protected.

Virginia Falls, on the Nahanni River, is higher than Niagara. It is the centerpiece of the newly expanded Nahanni National Park Reserve.

HARVEY LOCKE: The Nahanni National Park Reserve was all about creating a big northern anchor for the Yellowstone to Yukon corridor. That's why we worked so hard to expand Nahanni National Park Reserve, by six times. It operates at the scale of an entire wilderness watershed. It protects a population of about 500 grizzly bears, ranges of two or three caribou herds, a big population of Dahl sheep, an entire natural system, privileges it as one of the world's biggest national parks and one of its most beautiful places.

NARRATOR: Although far from complete, Yellowstone to Yukon has become a model for similar projects worldwide.

Eight countries in Central America have made initial efforts to protect the Mesoamerican Biological Corridor, known as the Path of the Panther.

In Australia, conservationists are working to connect protected areas for 2,000 miles along the east coast. The goal is to preserve the continent's iconic wildlife, including wombat, cassowaries and platypus.

In Asia, scientists hope to link parks across Northern India, Bhutan and Nepal. This area runs from the world's highest peak to lowland jungles and will help protect species like Bengal tigers and snow leopards.

Perhaps the most ambitious project outside of North America is in southern Africa, where five countries are cooperating to create the largest network of protected areas on the continent.

Angola, Botswana, Zambia, Zimbabwe and Namibia are working together to reassemble a landscape of over 150,000 square miles. It's known as the Kavango Zambezi Tranfrontier Conservation Area, or the KAZA TFCA. The network will link 36 parks across five nations.

These lands hold a number of great cats—lion, cheetah and leopard—as well as hippo, giraffe and a host of antelope species. At the heart of this region is Botswana, where Chobe National Park harbors the only large elephant population left in the world, numbering about 200,000. Here, biologist Mike Chase leads a group called Elephants Without Borders.

MIKE CHASE (Elephants Without Borders): One of the tools that the decision makers have had in delineating the boundaries of KAZA is to use the ranges of elephants: how far these elephants are moving within each of the particular countries, as well as identifying those critical linkages, those corridors, which areas connect the protected areas.

NARRATOR: To follow the elephants, Chase has to use jumbo-sized satellite collars.

MIKE CHASE: The process of darting, itself, is always…starts by identifying a focal area, a region we want to collar elephants in. So, the area we've identified for this collaring is a series of artificial water holes, where large numbers of elephants gather in the peak dry season.

We're looking to collar an elephant between the age of 20 and 25. It's these young bulls that have this propensity to really move vast distances to explore and reconnoiter new areas.

NARRATOR: Tranquilizing a three-ton elephant requires a powerful drug. The veterinarian handles these darts with care: a single drop would kill a human.

The darts are shot from a rifle, and although these bull elephants won't be harmed, approaching them with a pointed gun can be risky.

MIKE CHASE: Second from the left.

NARRATOR: It's a tense 15 minutes before the elephant falls asleep. The team hopes he won't run too far or enter a deep thicket. Sometimes he just kneels down, and the team has to give the sleeping animal a push.

MIKE CHASE: Okay, watch for that foot.

NARRATOR: Then it's time to attach the collar.

MIKE CHASE: The satellite unit is at the middle of the base of the neck.

Typically, the collars are on for a period of two years, and we get a G.P.S. location every hour during that period. We know, with pinpoint precision, where the elephant is, 24/7.

Okay, we're almost there, Larry, tightening these nuts.

NARRATOR: Since they can't carry a scale big enough for an elephant, they take body measurements to estimate weight.

MIKE CHASE: Three meters and four centimeters.

NARRATOR: This big fellow checks in at about 5,000 pounds.

MIKE CHASE: Follow his leg in the center.

NARRATOR: Elephants' ears are their cooling system. It's the best place to find a blood vessel to administer the antidote.

MIKE CHASE: Antidote's in, guys.

NARRATOR: It takes about five minutes for the elephant to wake up. Meanwhile, the team retreats to a safe distance.

MIKE CHASE: Collaring elephants is really critical to the work Elephants Without Borders is doing. So, the collars provide us with vital information on, not only the movements of elephants, but the habitats that these elephants need to survive. And with this information, it's a direct link I have with these elephants. It's a way of them communicating with me which areas they need, to move across this vast landscape.

NARRATOR: Elephants cover enormous territories in their search for food and water. An average elephant eats about 300 pounds of vegetation a day and drinks about 50 gallons of water.

Female, baby and juvenile elephants live in "breeding herds," 30 to 60 individuals, led by a matriarch. Using her encyclopedic memory, this grandmother guides her extended family to seasonal food and water supplies, across hundreds of square miles.

Increasingly, she must also keep track of which areas are safe from human conflict and poaching. Bulls live alone or in bachelor groups, until they enter musk and start searching for a mate.

MIKE CHASE: The information from collaring nearly 130 elephants, throughout the KAZA TFCA, has really provided new evidence on the spatial ecology of elephants.

NARRATOR: "Spatial ecology," as it's called, maps the lands animals need to live in and move through to meet their needs. Chase's collars have helped the Botswanan government see where cattle fences and human settlements are cutting off the elephants' migration routes. Since some fences were taken down, elephants have been tracked traveling from Botswana, across Namibia to southeastern Angola.

To get the big picture of elephant numbers and distribution, Chase has to get up into the air. To make accurate counts, he installs a pair of rods on each side of the plane to calculate how much ground they are covering.

Observers record every large mammal they see between the rods, and take photographs to confirm their numbers.

KELLY LANDEN: I've got a breeding herd, eight adult elephants and five juveniles.

MIKE CHASE: In addition to counting elephants, we will count sable, roan, eland, giraffe, kudu, hippo, in some cases. So, when we say we're counting elephants, we're really observing and recording a host of other wildlife species.

NARRATOR: But here, too, human settlements are an important factor. While much of Africa is sparsely settled, its human population has doubled in just 40 years. As more people come to live around parks, there's less room for animals, so conflict is inevitable.

THOMAS (Botswanan Herder): There's many elephants. there's lots and lots of elephants. During the rainy season, when they've planted their crops, elephants come in and crop raid, and it's a bad time of year, with conflict. If the elephant's in their cropland, they shoot it, and they report it to Wildlife. Wildlife will come and remove the tusks, and the meat is shared between the villages.

MIKE CHASE: To avoid human-elephant conflict and tragedies, such as this, we have to provide elephants with safe access to the migratory routes they've been using for thousands of years.

NARRATOR: Maintaining these ancient corridors is critical for the survival of animals and the safety of humans. People and wildlife are often killed in these conflicts. Wildlife patrols steer the elephants away from farmers' crops by shooting firecrackers, called "bear bangers." To limit conflict, the KAZA conservation effort is developing incentives so communities can see a benefit from wildlife.

SIMON MUNTHALI (Kavango Zambezi Tranfrontier Conservation Area): To ensure easy movement of wildlife across the KAZA landscape, it is important that we provide incentives for local communities, in particular, which now look at wildlife as some sort of economic asset for themselves, so that they should be able to benefit from wildlife. And once they are benefiting from wildlife, they are going to accept wildlife moving across their land, as well as contribute to protecting it.

NARRATOR: To encourage local support, Botswana has developed an ecotourism industry, which provides jobs and a cash economy. Other African countries would like to develop similar programs, but it depends on maintaining healthy wildlife populations and safe corridors to link protected areas.

But, just as elephants have begun to use the corridors, they have encountered a deadly threat. The ivory trade has spread to southern Africa and with it an epidemic of poaching. In one park, in southern Zambia, Mike Chase counted 281 elephant carcasses, and only 133 live elephants.

SIMON MUNTHALI: If poaching exists, wildlife will not move. Communities can provide land, governments can provide men and resources, but if we don't deal with poaching, wildlife will not move. That is the biggest challenge: poaching.

NARRATOR: Angola is a tragic case. It used to have the largest elephant population in Africa, 200,000 individuals. But more than half, at least 100,000 elephants, were killed to feed troops and buy arms during the long civil war of the 1990s. But after the war ended, the elephants began to return.

MIKE CHASE: Those elephants that weren't killed, we suspect, fled to the safety and security of Botswana. And when I first started this study, in 2001, we were able to document the repopulation of elephants, elephants moving back into these woodlands of southeast Angola, which coincided with the end of the civil war.

NARRATOR: The return of elephants to Angola provides important evidence that if international efforts to eliminate the ivory trade succeed, elephants will use safe corridors to repopulate their historic lands.

MIKE CHASE: The KAZA TFCA is one of the last great hopes for elephant conservation in Africa. If we can't get it right, in this corner of Africa, the prospect for elephant conservation elsewhere in Africa seems bleak. The repopulation of elephants in southeast Angola, going from a population of 100 elephants to 8,000, is one of the greatest conservation success stories in the last 50 years. And it's in that spirit and that optimism that I think that KAZA has the ability to be a refuge and provide a future for elephants in Africa.

NARRATOR: Elephants and other wild species, lions, grizzly bears and wolves, all require room to roam. Our national parks are essential to their survival, but conservation biology tells us they are not enough. The question is, are there ways to connect these parks so that the wildlife that makes them so special, can be saved?

DAVID QUAMMEN: To recreate connectivity, to allow our animals to move from one patch of protected landscape into another, we have to make some adjustments. Some of those adjustments involve adjustments to the landscape, like overpasses, and some of those adjustments are psychological, cultural and social. We need to find ways that people can live with wildlife and wildlife can live with people.

CRAIG PACKER: If we, as a species, we, as people, in Asia, Europe, North America, agree that we want these species to continue into the future, along with us, then we have to take that responsibility and have to find real mechanisms that will provide the resources in order to assure their conservation into the future.

MICHAEL SOULÉ: This era that we're in now could be a wonderful opportunity or a tremendous failure for humanity. It's our last chance to protect the diversity of life on Earth.