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00:00In the northwest corner of Wyoming lies a truly magnificent world, ringed by towering
00:14mountains, and a colossal dome of lava covered in pines.
00:28It's a land forged by the mightiest forces on our planet, tectonic collisions that have
00:35thrust granite peaks more than 13,000 feet into the sky, superheated geysers that explode
00:43out of the earth below, and raging waters that have the power to awe.
00:54Volcanic eruptions and wildfires have devastated its land, but its fertile valleys are still
01:00home to more mammals than anywhere else in the lower 48.
01:08With its staggering beauty, fragile creatures, and colorful springs that may hold secrets
01:18about the origins of life, this is one of the most remarkable ecosystems on earth, a
01:26place called Yellowstone.
01:56As soon as the first rays of morning light hit the great granite forms of the Tetons,
02:15on Wyoming's western border, you can already sense that this is no ordinary world.
02:28These are some of the most distinctive landforms in America.
02:33The tallest, known as Grand Teton, soars 13,770 feet into the sky.
02:42This giant hunk of granite has been pushing up out of the ground for just 10 million years.
02:48It's one of the youngest mountains in the Rockies.
02:52But the rock it's made of is some of the oldest on earth.
03:01The Tetons have been formed by a clash of tectonic plates in the earth's crust.
03:09As those plates collide, they trigger earthquakes, which push up layers of ancient rock, inch
03:15by inch, into these forms we see today.
03:20One reason the Tetons are so sharp at their tips is because erosion hasn't yet rounded
03:25the edges of these youthful mountains and whittled them down.
03:32Their jagged shapes are what make them so easily recognizable.
03:41The Tetons lie in the middle of what's known as the Greater Yellowstone Ecosystem, which
03:46stretches from southern Wyoming, across the northern corner of the state, west into Idaho,
03:53and north into Montana.
03:55And at the heart of this vast region are the 2.2 million acres of protected wilderness
04:01that make up Yellowstone National Park.
04:10When you descend into the valleys of Yellowstone, it can seem like a very peaceful world.
04:17But deep under these mountains, rivers, and forests is one of the largest and most destructive
04:24volcanic forces on the planet, a giant plume of rising magma known as the Yellowstone Hotspot.
04:34For the past two million years, this supervolcano has been responsible for catastrophic eruptions
04:40so powerful they've covered much of the continent with ash.
04:46But it's also what has given birth to many of the wonders of Yellowstone's landscape.
04:52In 1870, one man suddenly found himself lost and all alone in this forbidding world.
05:04His name was Truman Everts, and he was anything but a mountain man.
05:10He had been the Internal Revenue Officer for Montana, but was unemployed when he got the
05:15chance to take part in the first major expedition into the Yellowstone region on horseback.
05:22What happened to him here would soon be a warning to others about the risks of exploring
05:27this remote volcanic land.
05:31It all began in thick forests on the south side of Yellowstone Lake, when Everts somehow
05:36got separated from his fellow explorers.
05:39Soon after, his horse bolted, along with almost all of his supplies and his gun.
05:46By nightfall, he was completely alone in this wild landscape of lakes and trees.
05:53All he had left was a couple of knives, an opera glass, and the clothes on his back.
06:04Over the coming days, his fruitless search for his companions brought him to this river
06:11and the shores of Heart Lake.
06:14This is still one of the most remote areas of Yellowstone National Park today.
06:23Everts spent most of one night high up in a tree, trying to escape a hungry mountain
06:28lion that growled and paced the earth below him.
06:33In the days that followed, he suffered a remarkable series of misfortunes.
06:39He managed to lose both his knives.
06:44Not far from the lake, he slept near some thermal pools to stay warm.
06:48But one night, in his sleep, he rolled onto a steaming vent and scalded one of his hips.
06:57He even escaped a raging forest fire that he had started himself by accident, and had
07:03burned off much of his hair.
07:08Every day, he got more and more delirious, and old friends started speaking to him.
07:16One of these phantom companions encouraged him to forge on until he reached the Yellowstone
07:21River.
07:24It was on his 37th day alone in the wilderness that Everts suddenly heard a voice calling
07:33his name.
07:35It was a bounty hunter known as Yellowstone Jack.
07:40When Everts was finally rescued, he weighed just 90 pounds, and was what one man later
07:45described as nothing but a shadow.
07:48At first, he was mistaken for a small, mangy bear.
07:55Everts published an account of his survival, which he called 37 Days of Peril.
08:01Some questioned how much of it was true, but it succeeded in painting a picture of Yellowstone
08:06as a strange and frightening place, which only inspired others to want to come and see
08:12it for themselves.
08:15Today, the lure of Yellowstone is still just as strong as it was 150 years ago.
08:27This trail runs for almost 17 miles, up what's known as Specimen Ridge.
08:34It gives hikers the chance to experience the Yellowstone region just as Native Americans,
08:39trappers, and explorers did when they first made their way across these vast open spaces.
08:51Many parts of Yellowstone National Park are still as wild as they were thousands of years
08:57ago.
09:00One of them is the Hayden Valley.
09:16Under this morning mist lies one of America's most magnificent landscapes, a vast, fertile
09:24grassland fed by streams that wind through it like ribbons.
09:36Once the Hayden Valley was covered by the waters of a giant lake, but over time the
09:42lake retreated and eventually glaciers filled the valley.
09:48When those great rivers of ice melted roughly 13,000 years ago, they left behind deposits
09:55of clay and sediment.
09:59That nutrient-rich soil is what feeds the grasses of the Hayden Valley today, and has
10:05turned it into a prime habitat for some of North America's most powerful predators.
10:15It's early June, and the largest wolf pack in Yellowstone is on the hunt.
10:22Called the Wapiti Lake Pack, it's roughly 20 wolves strong.
10:28Some members of the pack are finishing off a recent kill, an elk.
10:32Today there are about 100 wolves inside Yellowstone National Park.
10:39Centuries ago, there were many more, but in the 1800s, westward expansion and hunting
10:46reduced their populations.
10:49And starting in 1900, U.S. government-sponsored hunts removed them from Yellowstone completely.
10:58In 1995, wolves were reintroduced into the park to try and restore this endangered species
11:06to one of their original habitats.
11:10They quickly made a comeback.
11:12Today, there are 11 different packs inside the park, and their tracking collars enable
11:19them to be studied and monitored.
11:22Each pack can range over hundreds of square miles in its search for food.
11:27But the Wapiti Lake Pack often hunts here in the Hayden Valley.
11:33These creatures may be top predators in Yellowstone, but they are surprisingly vulnerable.
11:38They often kill each other in battles over territory and mates.
11:45Some have been critically injured by the prey they hunt.
11:49One direct kick in the jaw from an elk can easily kill a wolf.
11:54And some wolves that have strayed outside the park's boundaries have been shot by hunters.
12:00But now, during springtime, these wolves have plenty of prey.
12:06And with a pack this big, they can even take down an adult bison.
12:14Peering down on Yellowstone National Park from above is a chance to witness an amazing
12:20array of creatures as they try to survive one more day in this wild, volcanic world.
12:28But it also may be the best way to understand how catastrophic geological events have formed
12:36and sculpted Yellowstone's mountains, valleys, and canyons.
12:50This 24-mile-long chasm, called the Grand Canyon of the Yellowstone, is one of them.
12:59The walls of this canyon plunge 1,200 feet into the earth and hold the waters of the
13:16Yellowstone River.
13:23Geologists believe it began its life as a long fracture in the earth created by volcanic
13:28forces as they pushed up the crust that covers the Yellowstone hotspot.
13:34Over time, thermal vents helped break up the lava that lined its walls.
13:43Water started running along the floor of the canyon, and erosion from wind, rain, and
13:48melting snow also oxidized and exposed colorful minerals in the earth.
13:57Some have claimed that the yellow walls of this canyon were the inspiration for the name
14:02Yellowstone.
14:04But it probably comes instead from a Native American tribe called the Minotauri, who named
14:10the river Stone Yellow.
14:13Or the sandstone bluffs that line its banks downstream in Montana.
14:21Where the Grand Canyon of the Yellowstone starts is one of the most captivating sights
14:26in the American West, the Great Cascade of Yellowstone's Lower Falls.
14:40When an early expedition of explorers arrived here in 1870, they climbed over rocks at the
14:46top and dangled strings daringly over the edge to try and measure the height of the
14:51falls.
14:54The legendary mountain man Jim Bridger had claimed they plunged 1,000 feet.
15:11Their actual height is 308, which is almost twice the height of Niagara Falls.
15:33During the last major eruptions of Yellowstone's supervolcano, roughly 640,000 years ago, massive
15:41quantities of magma poured out of the earth and filled in the floor of the volcano's giant
15:46caldera.
15:47The landscape these lava flows created wasn't very friendly to plants and animals.
15:58But over time, one species of tree managed to thrive on the shallow earth that covers
16:03all this hardened lava.
16:08They're called lodgepole pines, and they make up 80% of all the trees in Yellowstone.
16:18One reason this species thrives here is because lodgepole pines have shallow root systems
16:23that can cling to the thin layer of earth that covers the lava.
16:30But every year, wildfires destroy vast swaths of forest in Yellowstone.
16:36The largest series of fires in 1988 caused the entire park to be evacuated and burned
16:43close to 800,000 acres.
16:46But lodgepole pines have an amazing ability to regenerate, thanks to a secret weapon that
16:51they deploy when they are on the verge of death.
17:01These pine trees are equipped with a special kind of cone.
17:08Under intense heat from wildfires, they burst open and shoot their seeds out across the
17:13forest floor.
17:21As standing trees are engulfed in flames, they are already giving birth to new ones
17:26that will replace them.
17:30It's one of the many ways that Yellowstone's ecosystem is equipped to bounce back from
17:34catastrophic events.
17:46To keep an eye out for fires that could burn out of control, rangers are stationed here
17:52at this lookout tower.
17:56It stands on the summit of the 10,243-foot-high Mount Washburn.
18:06But with more than 10,000 hydrothermal features in Yellowstone, even rangers at this station
18:12need to have a trained eye.
18:20As heat and steam from vents, fumaroles, pools, and geysers hits the winter air, it's easy
18:27to believe that Yellowstone is being ravaged by fire.
18:31It can even look like there's an inferno raging under the earth itself.
18:40When European trappers, mountain men, and other brave souls journeyed into Yellowstone
18:45in the early 19th century, they often came back with fantastical tales of what they had
18:51seen.
18:52In 1829, a 19-year-old trapper named Joseph Meek wrote in his diary that the whole country
19:00was smoking with the vapor from boiling springs.
19:04Interspersed among these were larger craters, some of them four to six miles across.
19:11Out of these issued blue flames and molten brimstone.
19:17The largest hot spring in Yellowstone, called Grand Prismatic Spring, is enormous, with
19:24a diameter of 370 feet.
19:27That also makes it the third largest in the world.
19:31But it's nowhere close to the size that Meek described.
19:35Nevertheless, colorful and exaggerated tales like his got people more and more intrigued
19:42about this wild and remote region.
19:49By the middle of the 19th century, rumors were spreading about what lay inside the mysterious
19:55region called Yellowstone.
19:58After the U.S. government authorized the new territories of Montana and Wyoming in the
20:031860s, there was also growing interest by government officials to explore every corner
20:10of these new western lands.
20:13Finally, in 1870, the Surveyor General, a man named Henry Washburn, led the first major
20:21expedition into Yellowstone.
20:29On August 22nd, the 19 members of the party known as the Washburn-Langford-Doan Expedition
20:35set off from Fort Ellis in Bozeman, Montana, on horseback.
20:40This farm now lies on the site of that former fort, which is no longer standing.
20:46Washburn and the others made their way across the plateau and along the rim of the Grand
20:51Canyon of the Yellowstone.
20:54A few days later, they thought they saw smoke in the distance, but realizing it was actually
20:59steam, they celebrated.
21:01Finally, they were close to the mysterious thermal features they had heard so many stories
21:07about.
21:08When they reached the upper Geyser Basin, this was one of the very first sights they
21:13set eyes on.
21:17Since they thought it looked like turrets on a castle, they named it Castle Geyser.
21:23It still erupts every 10 to 12 hours and sends a stream of water up to 90 feet into the sky.
21:38As they mapped, measured, and documented everything they saw, they named many more of Yellowstone's
21:44impressive sights.
21:52After watching the waters of a small creek race through this narrow channel and then
21:56plunge to the valley below, they named this site Tower Fall.
22:03Since there are hundreds of waterfalls in Yellowstone, big and small, there were far
22:08too many for the expedition to name.
22:16One outcome of the Washburn expedition was that more and more scientists started getting
22:22curious about Yellowstone.
22:24In 1871, the Smithsonian Institution backed plans for a new expedition to thoroughly document
22:31the region's plants, animals, and minerals, and to map its lakes and thermal features.
22:39It was led by a geologist named Ferdinand Hayden.
22:44With them was a photographer, William Henry Jackson.
22:49Plugging 300 pounds of gear, including his large format black and white camera, Jackson
22:55took the first-ever photographic images of Yellowstone.
23:07But it was an oil painter on the expedition named Thomas Moran who brought it all alive
23:12in full-blown color.
23:23Hayden's most famous painting is of the Lower Falls, viewed from inside the Grand Canyon
23:28of the Yellowstone.
23:31The images and specimens that Hayden's team collected were put on display in Washington
23:36and helped energize a movement to convince the federal government to set aside and protect
23:41Yellowstone as a huge public park.
23:45It took three tries to get Congress to vote on the bill, but when it did, on February
23:5127, 1872, it passed with 115 votes in favor.
23:57And that's how Yellowstone National Park was born.
24:02It was the first piece of wild land in America set aside for recreational purposes to be
24:08managed by the federal government.
24:11Since then, 58 more national parks have followed.
24:22Soon after Yellowstone was created, a new mountain town in Montana called Gardiner began
24:28serving as its northern gateway, and still does today.
24:33Hikers and fishermen come here to outfit themselves for their journeys into the park.
24:39In 1903, a stone arch was erected to mark the entrance.
24:45When it was being built, President Theodore Roosevelt happened to be on vacation in Yellowstone.
24:53The masons convinced him to lay the cornerstone, and that's why the arch was named in Roosevelt's
24:58honor.
25:00Since then, millions of excited visitors have passed under it, eager to see America's first
25:05national park for themselves.
25:09Above them are the words,
25:11For the benefit and enjoyment of the people.
25:18Another major jumping-off point to the new park was the town of Jackson, Wyoming.
25:23It got its start as a fur trading hub, and like Gardiner, Jackson is also famous for
25:29an arch.
25:30In fact, it has four of them on its town square.
25:35Each one took about 10,000 pounds of elk antler to build.
25:42Jackson lies in the valley of Jackson Hole, along the Snake River, southeast of the Tetons.
25:49By the 1920s, a paved road had been constructed from Jackson into Yellowstone, and more than
25:56400 yellow tour buses were already shuttling visitors all around the park.
26:03Today, a few of these historic vehicles are still in operation.
26:10Yellowstone National Park covers 3,472 square miles of territory, but it has only 466 miles
26:22of roads.
26:28In the busiest month of July, they carry more than 30,000 visitors, which is three times
26:35the population of Jackson, and that's why traffic jams are common.
26:41But tourists are just the latest in a long history of those who have explored Yellowstone's
26:46hills, rivers, and valleys.
26:53Scientists have found evidence that Native Americans were here 11,000 years ago.
26:59Later, the region was used by ancestors of the tribes known today as the Blackfeet, Bannock,
27:06Nez Perce, Shoshone, and Umatilla, among others.
27:13Because of Yellowstone's harsh winters, most tribes came in the summer months to fish in
27:17its rivers, just like people still do today.
27:23They also came to hunt.
27:28The plateau's location between different Native American lands made it a convenient place
27:33for tribes to gather and train.
27:37One known meeting spot was here, on the north side of Yellowstone Lake, where Fishing Bridge
27:43now crosses the Yellowstone River.
27:54But Yellowstone had something else to offer, thanks to its volcanic past, a special kind
28:00of rock that was perfect for making tools and weapons.
28:06Deposits of it can still be found here, at Obsidian Cliff.
28:12These dark, jagged forms are actually volcanic glass.
28:17Today, surgeons use scalpels made from obsidian in some of the world's most delicate surgical
28:23procedures.
28:24But for thousands of years, Native Americans used it to make knives and arrowheads.
28:31By X-raying obsidian, researchers can tell which volcanic source it comes from.
28:37It's how they discovered that tools found in Native American settlements as far away
28:41as Ohio came from the walls of Obsidian Cliff in Yellowstone.
28:49It's powerful evidence of Yellowstone's rich human history, long before tourists flocked
28:56here to see its rivers, wildlife, and thermal features.
29:15The last major eruptions of Yellowstone's supervolcano happened more than 600,000 years
29:21ago.
29:23The next major eruption could obliterate Yellowstone National Park.
29:28But scientists say that's probably not going to happen anytime soon.
29:35But while Yellowstone could ultimately be destroyed by forces underground, much of what
29:40gives the park its life falls down from the sky, snow.
29:48Along Yellowstone's eastern border is a piece of the Rockies known as the Absaroka Range.
29:54If you follow the ridges of these jagged peaks, as they climb higher and higher, they will
30:00lead you right to the top of a snow-covered summit called Younce Peak.
30:10It touches the sky at 12,165 feet above sea level, and was named after a colorful character
30:17named Henry Yount.
30:20He was a 19th century hunter, prospector, Civil War soldier, and the first official
30:26gamekeeper of Yellowstone National Park.
30:32Come winter, this is a harsh, uninhabitable world.
30:37But Younce Peak and its surrounding mountains are also the life force of Yellowstone.
30:48Over millennia, snowmelt from these giants has flowed down into the valleys below and
30:54converged to create the Yellowstone River.
30:59For months at a time, this river is covered by snow as it winds through the Thoroughfare
31:05Valley.
31:07This valley has been called the most remote piece of wilderness in the Lower 48 because
31:12it lies more than 20 miles from any road.
31:17To aid those who venture this far into Yellowstone's interior, a National Park Service ranger is
31:22posted here at the tiny Thoroughfare Ranger Station.
31:27Over the years, these rangers have rescued many injured hikers.
31:31They are also here to nab poachers who venture illegally onto park land.
31:38But when the snow arrives, this lonely outpost is shuttered for the harsh winter ahead.
31:46This valley got its name, the Thoroughfare, because it was once the primary route that
31:51Native Americans and fur trappers used to get into Yellowstone from Jackson, Wyoming,
31:56to the south.
31:59In winter, their early trails probably looked a lot like this one, made by the snowshoes
32:04of hikers as they crossed the frozen waters of the Thoroughfare Valley.
32:10Like them, early travelers also carved holes in the ice to get to water and fish below.
32:20Under this frozen wilderness, the Yellowstone River continues its journey.
32:27Its waters are the source of one of Yellowstone's wonders, a 132-square-mile body of water that's
32:35the largest high-elevation lake on the continent.
32:40Yellowstone's last major volcanic eruptions left behind a giant caldera.
32:46Over time, water from the Yellowstone River and the surrounding mountains filled it up
32:51and created Yellowstone Lake.
32:55The floor of this lake drops to a depth of 390 feet.
33:00And like the ground all over Yellowstone, it, too, is riddled with active thermal vents.
33:07But in the winter, the top two feet of the lake are still often solid ice.
33:19On the north side, the Yellowstone River emerges again to begin a slow, winding journey
33:25through the Hayden Valley.
33:28This is a frequent gathering spot for one of Yellowstone's most fragile species, trumpeter's
33:36swans.
33:37With a wingspan that can reach eight feet across, they are the largest wild waterfowl
33:44in the U.S.
33:46This shallow, slow-moving section of the Yellowstone River is a perfect place for them to feed
33:52on plants underwater, even in the middle of winter.
34:02Less than a century ago, this species was almost extinct in North America.
34:08Environmental protections helped them make a comeback.
34:12And by 1961, there were 72 swans inside the park.
34:20But since then, their population has been declining.
34:24One reason is that swans have become prey for eagles, which used to feed primarily on
34:29native cutthroat trout.
34:32But then a non-native species of trout invaded Yellowstone's rivers and lakes.
34:38Now the eagles hunt swans.
34:42Just 29 of these graceful creatures are left in Yellowstone, and scientists are working
34:47hard to try and save this species before it disappears completely.
35:03The average elevation of the Yellowstone Plateau is 8,000 feet above sea level.
35:10And in the middle of winter, temperatures here can drop to 40 degrees Fahrenheit below
35:15zero.
35:18High up in the mountains, recorded annual snowfall has been known to hit 30 feet.
35:31By February, many lakes throughout the Yellowstone ecosystem are frozen solid.
35:37And that's exactly what some locals eagerly wait for so they can head out, brave the cold,
35:44and fish.
35:47East of the park's boundaries lies the Lower Sunshine Reservoir in Matitsi, Wyoming.
35:53Today it's just one giant sheet of solid ice.
35:59It's also the site of the annual Matitsi Ice Fishing Derby.
36:03Every year teams come here and spend a day on the ice to see who can catch the biggest
36:08fish.
36:09The team that catches the six longest and fattest fish wins.
36:15Most are cutthroat and rainbow trout.
36:19This year, the winning team's six fish measured in at 189.75 inches.
36:31For creatures all across the Yellowstone region, the beginning of every winter is the start
36:37of another tough six-month battle for survival.
36:41And there's no better place to witness that battle than here, the Lamar Valley.
36:50It's where bald eagles journey out of their nests to hunt and scavenge leftovers from
36:55the kills of gray wolves.
37:03Above the Lamar Valley, bighorn sheep use the steep, rocky landscape to hide from predators.
37:10Like many of Yellowstone's creatures, they find safety in numbers.
37:18But nearby, a ewe has been left behind.
37:23With a lame front leg, she struggles to get through the deep snow.
37:28She's the perfect target for a pack of Yellowstone's wolves.
37:33But she hasn't been spotted yet.
37:44In a land that's plunged into a deep freeze for most of the year, Yellowstone's creatures
37:50have had to hone their survival skills.
37:57Winter is particularly hard on one species, bison.
38:03Weighing up to 2,000 pounds, they have to move constantly to find enough nutrition to
38:08survive until spring.
38:11This herd is following a migration route along the Firehole River.
38:15When bison do find food, they usually graze until it's all gone.
38:25Once, these creatures blanketed the Great Plains by the tens of millions.
38:30Native American tribes took part in annual bison hunts and used just about every part
38:35of the animals they killed for food, shelter, and tools.
38:40After Europeans started fanning out across the West, bison were slaughtered by the tens
38:45of thousands for their meat and skins, and sometimes just for entertainment.
38:52Within a few decades, America's bison were almost extinct.
38:56Today, roughly 5,000 of these creatures inhabit Yellowstone.
39:02It's the only place in the nation where bison have lived continuously since prehistoric
39:07times.
39:12The large humps on their backs are just big bundles of muscle that provide extra power
39:17to a bison's head to help them clear snow so they can access grasses below.
39:25But winter grasses have about as much nutrition as cardboard, so without reserves of fat built
39:32up during the summer months and thick coats, these animals wouldn't be able to survive
39:38winter in Yellowstone.
39:42And many don't.
39:45Nine percent of adults won't make it until spring.
39:50Baby bison are even more vulnerable to the cold and lack of food.
39:55Every year, up to 40 percent of the park's youngest bison perish during the winter from
40:00exposure, predation, and accidental death.
40:09Yellowstone can be dangerous and even deadly for humans, too.
40:16Every year, at least one or two visitors to the park are gored by bison after getting
40:22too close for photo ops and selfies.
40:26And in 2018, two women were kicked by elk near a Yellowstone hotel.
40:32At least 20 people have died in the park's thermal pools.
40:37Most fall in accidentally, but in 1981, a man decided to dive into a pool that was 202
40:44degrees Fahrenheit to try and save his friend's drowning dog.
40:48Neither he nor the dog survived.
40:53But for hikers out in Yellowstone's backcountry, one of the biggest potential dangers is a
40:58mother grizzly with cubs.
41:02Bear attacks in Yellowstone are rare, but since 1872, at least eight people have been
41:08mauled to death by bears inside the park.
41:13One happened surprisingly close to the main road.
41:18It was about 8.30 a.m. on July 6, 2011, when a couple from California parked their car
41:24in this lot at the northern end of the Hayden Valley.
41:29This is the starting point of the Wapiti Lake Trail.
41:34As they set out for a day hike, they passed a sign that read, danger, you are entering
41:38bear country.
41:43The couple headed east across this open hillside.
41:48Their first destination was Yellowstone's Clear Lake.
41:52After they left the forest, another hiker alerted them to a mother grizzly and her two
41:56cubs foraging in a field below them.
41:59The couple photographed the bears, which still looked like tiny dots in the distance.
42:05They didn't appear to be a threat, so the couple continued on and crossed Hot Spring
42:11Creek.
42:16But swarms of mosquitoes quickly forced them to turn back.
42:22That's when they spotted the mother bear again.
42:25But now she was much closer, just 100 yards away.
42:30As the couple turned and headed toward the trees, the mother grizzly spotted them.
42:38Suddenly, she started to charge.
42:45The man and his wife began yelling as they ran into the forest.
42:50Within seconds, 500 feet up the trail, the grizzly caught up to them, knocked the man
42:55down, and mauled him to death.
42:58She turned back to find his wife, who was hiding under a fallen tree just 15 feet away.
43:05The grizzly picked her up by her backpack and put her down again, uninjured.
43:12Then she left.
43:18At the time of the attack, the couple was less than a mile and a half from their car.
43:24Since that day, there have been two more fatal bear attacks inside the park.
43:31At the scene of one of these killings, park officials found DNA from the same mother grizzly
43:36that had mauled the man in 2011.
43:39They also found disturbing evidence that she had fed on human remains.
43:45Fearful that she might now consider people as food, the park superintendent decided to
43:50find the bear and put her down.
43:54Her cubs were spared and sent to the Toledo Zoo.
44:07Every hiker in Yellowstone National Park who has suddenly found themselves face-to-face
44:13with a grizzly knows just how terrifying these giant predators can be.
44:20Males, like this one, foraging on the western side of the Hayden Valley, can weigh up to
44:26700 pounds.
44:29They are Yellowstone's apex predator, not just because of their size.
44:35Their bone and muscle densities are 10 times that of humans.
44:42They can bite, scratch, and maul with more power than any other predator in North America.
44:50But grizzlies aren't just carnivores.
44:53Up to 90% of their diet is made up of plants, roots, and berries.
44:58Usually, they only attack humans when they feel threatened or get surprised.
45:05But with an estimated 150 grizzlies in Yellowstone, it's easy for bears and people to get dangerous
45:12close.
45:20Beginning in the fall, thousands of elk from Yellowstone's southernmost mountains migrate
45:26down to the valleys below.
45:29Many head outside the park's boundaries and gather here in Jackson Hole.
45:35They come to escape Yellowstone's deep freeze.
45:40In 1912, close to 25,000 acres were set aside for elk on land just north of the town of
45:47Jackson.
45:49This is the National Elk Refuge.
45:52It's home to one of the largest herds of elk in the nation.
46:00Once tens of thousands of these creatures wintered here.
46:05But roads, development, and hunting have reduced that number to less than 7,500 today.
46:12Elk breed in the summer and fall.
46:15And so by February, the cows are late in their eight-and-a-half-month pregnancy.
46:20To conserve energy, most spend their days resting on the valley floor.
46:28The bulls are often the ones that head up to the high slopes to forage.
46:36In early spring, the antlers on the bulls naturally loosen and fall off.
46:42It's a way for these animals to reduce the calories they need to survive.
46:53By the time elk begin their migrations down from Yellowstone's mountains, the park's
46:59human visitors start to dwindle to a trickle.
47:04In winter, there's only one road open into Yellowstone from Gardner, Montana.
47:11For about seven months of the year, from October to May, much of the park is completely inaccessible.
47:20Most of its hotels and lodges are closed.
47:25Deep snow blankets the normally crowded boardwalks that line many of the park's most visited
47:31sites like this one, Norris Geyser Basin.
47:36During these months, some visitors get around the park on groomed snowmobile trails.
47:42Others use official snow coaches, which are really just shuttle buses that ride on giant
47:47snow tires.
47:50With so few human noises in Yellowstone during the winter, this is the time when the park's
47:56ancient soundscape can be heard in its purest form.
48:02The silence of its vast, open spaces, muffled by snow, the howl of winter wind whipping
48:13around jagged peaks, valleys that echo with calls of the wild, and the crackling sounds
48:29of shifting ice on Yellowstone's streams.
48:40But also the endless sputter of mud pots bubbling away in the wilderness, and the sudden rush
48:50of geysers exploding into the sky.
49:01Sounds like these have been echoing across the greater Yellowstone ecosystem for tens
49:07of thousands of years, while the snow-covered peaks of the Tetons have been climbing higher
49:16and higher into the sky, and great winter snowfalls have been feeding the rivers that
49:24race and plunge through Yellowstone's canyons.
49:29But what makes this volcanic landscape truly unique is how it supports so many different
49:35forms of life, and some of the most fascinating ones are invisible to the naked eye, until
49:43they cluster together by the billions.
49:49The brilliant yellows, oranges, and greens of Grand Prismatic Spring are actually the
49:55colors of unique microorganisms called extremophiles.
50:00Since they thrive in extreme conditions, scientists hope they might hold clues about what life
50:07could look like on planets like Mars.
50:12With everything from tiny microbes to towering predators, Yellowstone is one of the greatest
50:19natural laboratories on Earth.
50:23It's not surprising that there have been so many fantastical tales about this strange
50:28and beautiful place, and why even those lucky enough to see it for themselves can have a
50:34hard time believing that it's real.