Nearly 4 million people visit Yellowstone National Park every year, but if they get a glimpse of wildlife, it's likely fleeting and from a distance. For a closer look at animal behavior and all the drama inherent in living in such a place, there's "Wild Yellowstone," a two-hour Nat Geo Wild special premiering Dec. 6.

From production studio Brain Farm, known for its action sports documentaries, "Wild Yellowstone" applies heart-stopping camera techniques to epic battles for dominance from elk and bighorn sheep, grizzly bears and wolves and even hummingbirds defending their territory.

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Divided into "Grizzly Summer" and "Frozen Frontier" (the latter won awards for editing and cinematography at the Jackson Hole Wildlife Film Festival in October), the documentary kicks off a year of Nat Geo Channels programming marking the centennial of the national parks. Bringing it to the screen took a year of planning and nearly another in the field, according to Brain Farm producer Tom Stephens, who weighed in on the production along with other members of the crew.

A hummingbird gathers nectar in a still photo from 'Wild Yellowstone.'A hummingbird gathers nectar in a still photo from 'Wild Yellowstone.' Some of the hummingbird sequences were shot using drones. (Photo: Nat Geo Wild)

"Yellowstone is a very controlled environment. It's our oldest national park and it's probably got some of the strictest laws enforced by the rangers, quite rightly, on a film crew," says Stephens. "We had to be exemplary in how we were filming, because it's a very fragile ecosystem. We had to work out the access so we could find the animals at the right time of year. It was a lot, lot tougher than I was expecting," he admits. "The winter show in particular was a punishing experience for the crew. We had one team that was there for five weeks staying in a yurt, in negative 40 [degrees], trying to film otters and foxes in deep winter. They were carrying all their gear, cross country skiing, breaking down in the snow truck. But we got some fantastic sequences."

One of them is of a determined fox diving in the snow to catch a vole, shot in super slow motion, and obtained on the penultimate day of a five-week shooting expedition. According to Brain Farm CEO and cinematographer Curt Morgan, you need the luck of being in the right place at the right time, and have a lot of patience. "Behavior is really hard to shoot. But it really teaches you to live in the moment," he says. "And I loved the fact that the animals didn't talk back."

Dawson Dunning films a bison rut in Yellowstone Lamar Valley for 'Wild Yellowstone'Dawson Dunning films a bison rut in Yellowstone Lamar Valley for 'Wild Yellowstone.' (Photo: Theo Jebb/National Geographic Channels)

Cinematographer Dawson Dunning was responsible for shooting footage of beavers, hummingbirds, and bison and elk ruts — mating behavior including fights for supremacy. "The most dangerous one to film was the bison rut because the bulls are so testosterone-driven," says Dunning. "They don't care if people are in the way when they're crisscrossing the road, and they can be coming from behind you. They're pretty unpredictable. People have gotten gored trying to get close to take pictures. I don't get to close to the herd because the situation can change very fast."

Brain Farm's state-of-the art camera arsenal included Red Epic, Phantom Flex 4K for ultra HD, a gyro-stabilized truck-mounted $500,000 Shotover system used to keep the image steady while shooting sequences like the elk rut, bighorn sheep rut and a bear on the move, and handheld MOVI systems, the latest in Steadicam technology.

"We got shots of geysers going off with a MOVI," says cinematographer Ryan Sheets. "It’s quite heavy so it’s a workout, but you can’t do it without this gear. It's incredible picture quality, and the surround sound is amazing too."

An aerial view of the Grand Prismatic Spring in Yellowstone National ParkAn aerial view of the Grand Prismatic Spring in Yellowstone National Park. (Photo: Steve Rogers/National Geographic Channels)

Although Old Faithful is the best-known geothermal feature in Yellowstone, there are more than 10,000 geysers, hot springs, mud pots and steam vents in the park. "We filmed them in winter, and we were getting a half-foot of snow every day," remembers Tom Stephens. "We were trying to build cranes and get a view over these pools that you can't get as a tourist and show people something really different and unique."

Other overhead shots were accomplished via helicopters and a really long lens. Drones are not permitted in Yellowstone, though they were used outside of it, in "the greater Yellowstone ecosystem, where the hummingbird sequence was also shot," Curt Morgan notes.

To get intimate shots of a beaver family inside their partly submerged lodge, cinematographer Jeff Hogan went old-school. "The lodge had a hole in the top and it collapsed in, so I slipped a little digital SLR camera down in it and that's how we did it."

Getting the winter footage — like video of the otters above — was decidedly more difficult. "The roads are closed off in the winter and the only access is by snowmobile or snow coach, with big rubber tracks so they can go over snow," says Dunning. "We had to charter our own so we had full access to where we wanted to go." The hardest part? "Carrying a lot of gear in 35 below, waiting for a fox to do something."

Fortunately, the expensive gear held up pretty well in the freezing cold. "You only have to worry about cables breaking. They're pretty sensitive," Dunning says. His favorite shots include a bear eating a bison and a bobcat defending its kill, a swan, against a coyote. "All the coyote got was a feather."

A mother bear and cub cuddle together in the fields of Yellowstone National ParkA mother bear and cub cuddle together in the fields of Yellowstone National Park. (Photo: Nat Geo Wild)

These critter encounters look as if they were taken from close range, but the cameramen kept safety in mind at all times. "You have to stay 100 yards from bears, which is a good idea," says Theo Jebb, who shot a lot of the grizzly bear footage with John Shire. "I never felt in danger." Adds Ryan Sheets, "You’re hyper aware of where you are and how far away you need to be, and that prevents close calls."

Whether one visits the park or not, "There is a huge part of Yellowstone that most people don't ever get to," says Brain Farm head of production Chad Jackson. "I think our mission is to showcase the beauty of wildlife and nature so people respect it and want to preserve it. The most important message here is to respect nature. Maybe that will get more people involved in wanting to protect parts of Yellowstone."