EMIGRANT, Mont. — Doug Peacock returned from Vietnam in 1968 a different man than when he left. His mind was eating at him. He and other war veterans didn’t have words for the disease from which they suffered. Later it would be identified as post-traumatic stress disorder.

Needing to be away from people, Peacock fled to the wilderness, camping high in Wyoming’s towering Wind River mountain range. Following a bout of malaria, he made his way up into Yellowstone National Park, where he came face-to-face with grizzly bears.

“I wasn’t looking for them, but they were there,” Peacock, 75, recently told HuffPost on the patio of his home in Paradise Valley, just north of the park and overlooking the Yellowstone River.

These dominant creatures proved exactly what Peacock — a former Green Beret medic, prolific author and the inspiration for Edward Abbey’s fictional character George Washington Hayduke in The Monkey Wrench Gang — needed; a species that, as he puts it, anchors your attention and gets you out of yourself.

“It’s the one animal on this continent at least, maybe anywhere, that refutes the whole notion that homo sapiens are in charge of every fucking thing,” he said. “The one animal that can remind the most arrogant fucking species on Earth what their true place is on the Earth, in nature, in their own hearts.”

“What you are is what you evolved with,” Peacock added. “We didn’t evolve in cities and towns and shit like that. We evolved as hunters and gatherers, in places whose remnants today we call the wilderness.”

Years after returning scarred from war, and after countless days tracking and filming bears in grizzly country, Peacock wrote in his first book, Grizzly Years: In Search of the American Wilderness, that the animals saved his life. Of course, any one of them could have just as easily taken it.

For the better part of five decades now, Peacock has been a fierce advocate for the grizzlies. And today he is among the lead plaintiffs in a lawsuit against the federal government over its decision to remove Yellowstone grizzlies from the endangered species list.

Marc Beaudin Doug Peacock, a Vietnam War veteran and longtime grizzly bear advocate, is among those suing the U.S. government over its decision to remove federal protections for Yellowstone grizzly bears.

Peacock is an expert in grizzly behavior; no surprise considering the amount of time he’s spent living and studying in grizzly country, out of a tent and mostly by himself. Over the years, he’s been charged by dozens of bears, almost all of them mothers protecting cubs. The run-ins, he says, were his fault and come with the territory.

Along with finding solace in the Rocky Mountains, Peacock learned how to avoid becoming a grizzly’s rag doll. The key, he says, is to avoid making eye contact, and to keep from making any sudden movements or screaming. Just hearing him talk about his closest encounters is enough to make the average person’s heart race.

One of Peacock’s favorite bears was a dominant, black-coated male he ran into often ― “the baddest son-of-a-bitch in the mountains,” Peacock said. Over a handful of summers in Glacier National Park, he and the bear developed a relationship of sorts. On one occasion, when Peacock walked away from his campsite high on a mountaintop, the bear pulled his cache of gear out of a tree and chewed to pieces his sleeping bag and a dirty T-shirt. “He ate everything that smelled of me,” as if to say “get the hell off my mountain,” Peacock said. Another time, that same grizzly caught Peacock away from his camera, knocked it off its tripod and chewed on it.

“He was a good bear,” Peacock said, without even a hint of sarcasm. “That’s what a bear should be.”

James Hager / robertharding via Getty Images A grizzly bear walks in Yellowstone National Park, in Wyoming.

A couple of times, a grizzly came skidding to a stop right in front of him. One female stopped just six feet away, then leaned forward and stuck her nose out to sniff his pant leg.

“I always stood my ground,” he said. “I don’t look at the bears, I kind of hold my arms out. I don’t move a fucking muscle, all the time they are charging.”

One of Peacock’s most recent encounters was in June, when he and his daughter were resting on a high butte in Yellowstone; their last hike together before he walked her down the aisle. It was a “windy goddamned day,” he recalls. All of a sudden, the look on his daughter’s face changed. There, some 50 feet away, a mother grizzly and her yearling cub were coming over the hillside.

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“Everybody sees each other at the same time,” Peacock remembered. “I think I probably say, ‘Don’t move.’”

The mother quickly reared onto her hind legs. Peacock and his daughter stayed still and eventually, after a couple of minutes, the bear calmed down. Then, the bears slowly walked by and sat down on the edge of a cliff 30 feet away, where the mother began nursing the cub. This went on for five minutes, Peacock says. In the distance he could hear the bellows and roars of male grizzlies, indicating the female had likely retreated to high ground to keep her cub away from aggressive bears looking to mate.

There’s a huge misunderstanding about these magnificent creatures, Peacock says, which for the most part have no interest in humans.

“We fear what we don’t know, and we hate what we fear,” he said.

Chris D'Angelo/HuffPost The remains of a grizzly bear lay along the bank of the Yellowstone River, near the town of Emigrant.

In addition to writing several books, Peacock is a co-founder and long-time board member of Round River Conservation Studies and works with traumatized veterans to expose them to the benefits of the outdoors. And he continues his decades-long fight to ensure grizzlies continue to thrive.

The U.S. Fish and Wildlife Service first delisted the Yellowstone population of grizzlies from the Endangered Species Act in 2007. Environmental groups sued; Peacock was among the plaintiffs. In 2009, a federal judge overturned the government’s decision, ruling that FWS had not considered the impacts the loss of white bark pine trees could have on the population. The decision restored protections for the Yellowstone grizzlies.

But in June of this year, federal authorities announced that Yellowstone grizzlies had recovered to the point that they no longer required federal protection. The Interior Department estimates the population to be around 700 bears ― up from as few as 136 in 1975 ― and said multiple factors indicate it “is healthy and will be sustained into the future.”

A month before the delisting took effect on July 31, a group of conservation nonprofits and the Northern Cheyenne Tribe promised to sue. And on Aug. 30, they did just that. It’s one of several complaints aimed at restoring ESA protections for the bears.

With the impacts of climate change becoming undeniable, it is a critical time for the Yellowstone grizzly, according to Peacock.

“The [Fish and Wildlife Service] wants to declare a victory,” Peacock said. “They’ve done an incredible job of bringing back the grizzly since 1975 in Yellowstone, but with climate change, global warming, that population will never be recovered. None of us will.”

In its final rule, published in July, the FWS concludes that “the effects of climate change do not constitute a threat to the [Yellowstone] grizzly bear [population] now, nor are they anticipated to in the foreseeable future.” But the seeds of white bark pine, a high-elevation tree that has been severely impacted by disease, insects and climate change, are an important food source for Yellowstone grizzlies.

Peacock’s most immediate concern is hunting. State jurisdiction in Wyoming, Montana and Idaho opens the door for limited hunting of grizzlies outside Yellowstone.

“It’s the thing that scares me the most, because it won’t just be a hunting season,” Peacock said. “It will be the whole pulse of the value of a grizzly bear, how easy it is to kill, how expendable they are.”

For Peacock, you can’t put a price tag on such a creature. Just like you can’t put a price tag on wild places.

“It’s late in the game. I’m not going to be around that much longer,” he said. “But boy have we fucked up, man. I feel bad. Both my kids are getting married this summer. You know, if I could hang on another year I’d probably see a grandkid. But man, what they’re going to inherit — it’s going to be tough.”

“That’s what I’ll do the rest of my days,” he said of fighting to protect the natural world.

The video below, titled “Happy Bear,” was shot by Peacock in the late 1970s in Montana’s Glacier National Park: