Humility.

We've been walking slowly through the dark for a long time, the old soldier and I, beneath a thumbnail silver moon, the coyotes chattering like roosters. He makes his way using a wooden flagpole for a cane, a rifle and a tripod strapped to his back. Here, some 30 miles north of Yellowstone, at the edge of Montana's Crazy Mountains, on this cold morning in November, the mind feels clean and clear, focused on this one moment. We're hoping to kill an elk at daylight.

Doug Peacock has barely hunted, or even fired a gun, since his days in Vietnam. He experienced enough killing there, he says, to last several lifetimes. He was 27 when he came home, racked with PTSD, back before there was a name for it — his Army medical papers described his condition as: "Occupational and social impairment . . . due to such symptoms as: depressed mood, anxiety, suspiciousness, panic attacks, sleep impairment . . ."

Peacock thought he was alone back then; he didn't know that every soldier experienced some version of this. Once home, he wandered the West — Utah, Arizona, Wyoming — in solitude for weeks at a time. Eventually, he found his way into Yellowstone country, just a day's walk from the sagebrush prairie we're traversing this morning. In the small number of grizzly bears that were holding on there, Peacock found something worth living for. He began to follow those bears — tracking them year after year, getting to know them, filming them. Over the years, he came to understand them in ways few others, if any, had before. Now no one knows wild grizzlies better. Other researchers fly over them in airplanes, and many good scientists sit in front of computers doing the important work of spatial modeling and scat analysis. But for nearly his entire adult life, Peacock has been out with the bears — in their country, watching and learning. "It's the one animal out there that can kill and eat you anytime it chooses to — even though it seldom does," he says. "It stands as an instant lesson in humility."

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