Wives and husbands come and go, children leave, friends fade into abstractions on Facebook. The dog is generally there for life, all of his or all of yours, whichever comes first. Hunter, who died Sunday night at home and surrounded by his people, was there for life. It was really his second life, which began when I pulled his numb body from a freezing, half-empty swimming pool 10 years ago this month.

His first life remains a mystery, although we were able to reconstruct the basics over time. He had belonged to a family with little kids of stroller age, because for the first year or two he would dash off after any such a family we saw hiking in our regional park. Once he got close enough to see them clearly, the tail would stop wagging and he would come back to his new people, his usual good mood deflated for a while. His other family had a light-colored Toyota Highlander or Honda Pilot, because whenever Hunter saw one of those parked at a trailhead, he got up on his hind legs to look inside.

But he had been dumped out in the desert, many months before his near death in the filthy icy waters of my closest neighbor's above-ground swimming pool in a humble neighborhood on the edge of town. The black dog's frayed and too-tight collar had no tags, and he had no identification microchip beneath the skin of his back. There were no "Lost Dog" ads matching his description. The neighbors, a bunch of mean old people, had been calling Animal Control whenever they saw this stray dog looking for food or companionship. For months, he had lived by his wits in the harsh waterless environment of Northern Nevada's Great Basin, raiding garbage cans and learning to hunt the impossibly fast jackrabbits. The latter skill he found hard to forget, as I witnessed more than once while hiking with him in the backcountry.

For water, on the cold day after Thanksgiving 2003, he had tried to reach the slowly evaporating muck in this trashy swimming pool on the slope above my own run-down home. And on this day, his luck ran out. He plunged in and paddled in panicked circles until, in a moment of inspiration, he lodged his front paws into the filter intake. Then he began howling.

The sound was terrible and weird, an ongoing cry of desperation and pain. We heard it inside, my wife and I, and wondered if it was one of the wild mustangs that lived in the hills there. The howling continued, somehow louder now, despite the lack of a visible source. She went out for another look around. And this time, at just the right moment, the dog used the last of its strength to raise his head just enough to be seen. He looked right into her eyes.

I was called to assist, got down on the ground and reached toward the water, getting my arms around his barrel chest just as I realized grabbing a big stray dog was fundamentally dumb. Even in his moment of terror, his brown eyes were kind. I pulled him to safety. My wife was there to help steady him, but he collapsed anyway because his legs were numb.

We got him inside by the fire and toweled him off. Soon he was standing on his own, lapping up a saucer of water.

"You're alive, so off with you," I said, figuring he belonged to a neighbor with casual views about pet care. It was dark when I returned home, many hours later, and he was waiting at the door. Our property was unfenced, front and back, and we had no money to change this situation. For the dog to stay, as my wife now wanted, I required evidence of housetraining and other indoor-appropriate behavior. He also reeked of rotten garbage, so I insisted that my wife bathe him. It took four tubfuls to get from black water to something approaching clear, and with that he was shown to an old blanket by the fireplace, where he curled up and slept for 12 hours straight.

On the bookcase above him was a thick collection of Hunter Thompson's letters. And that's how the dog got his name, which was entirely appropriate for a jackrabbit-catching mutt comprised of German Shorthair Pointer and Labrador Retriever. He awoke in a remarkably cheery mood, considering the months-long Hell he had just escaped, and I used a length of rope for a temporary leash. We walked into the desert hills, the lead stretched tight as I tried to keep up. Deep in a canyon, I let him off leash and he raced this way and that, always staying within sight of me. I quickly figured out he had no intention of running away.

Over the next 10 years, we walked at least three miles a day with frequent longer hikes, a minimum of 11,000 miles. We walked the sagebrush flats of the Eastern Sierra, the horse trails of Griffith Park, Mojave Desert foothills of juniper and Joshua trees, beaches from San Francisco to San Diego, through winter snows so deep I could only see Hunter's black head plowing through a sea of white.

He gave snakes plenty of room, paid no mind to desert tortoises, and took particular joy in standing atop the highest boulder. For years he rode shotgun wherever I drove, often up and down the most beautiful road in the world, Highway 395 between Los Angeles and Reno, returning often to our favorite spots in the Alabama Hills and the Forest Service lands around Bishop and the wild riverbanks out past Bridgeport. In each place we lived, there was a default three-mile loop, and the best of those went from our house alongside a national park to a high-desert forest just over the boundary line, a minor violation of policy we practiced daily.

A dog's life races by, and his once-black muzzle turned white in his old age. He developed white eyebrows, too, and spoke volumes with them. Enduring as a stray and surviving a near-drowning should've been enough escaped death sentences for any creature, but over the years he was diagnosed with any number of ailments expected to kill him shortly, including a massive muffled heart and a severe infection from a broken tooth that was repeatedly mistaken for everything from a rattlesnake bite to a collapsed immune system. A year ago, he was found to have a thyroid condition and put on medication for his last days, until another vet said there were no symptoms requiring such a pill regime.

His impending death went on for so long that I quit believing he would ever die, because all the while we did our thing, running and walking and exploring every day, and his growing creakiness this year was the only real evidence of the inevitable. The stiffness of old age did nothing to change his insistence on going out every morning and every evening and pretty much whenever I made a movement that could be interpreted as preparing for a walk. If my coffee cup accidentally bumped against my keyring, he was at my office door with hopeful eyes and thunking tail.

He could be annoying and he could be needy, especially when I was racing to finish some writing and his intrusions broke my flow. That’s the nature of an unfair relationship—he could not leave the house without me—and to his own wise old eyes I’m sure I was a regular disappointment. But unlike people, who hoard and revisit their grudges forever, Hunter forgave quickly and completely. "Old dogs care about you even when you make mistakes," as Tom T. Hall wrote.

Hunter's 10 years with me were busy ones for his humans. Babies appeared and he welcomed them graciously and gently, even as they grew into tail-pulling toddlers and the forces of loudness and chaos known as little boys. They were accepted into the pack and placed in the appropriate rank, and he bravely ran off the teams of coyotes that approached his family's territory. In a time when he deserved the peaceful routine of retirement, we moved him to the city and he stoically became an urban dog, now bound to leash laws and not nearly enough weekends on the beach or trail. I arrived home after a late flight last month to a jubilant greeting of such energy that he insisted on running for several blocks with me, the leash coiled in my coat pocket, one more ceremonial breaking of the law on the empty late-night streets.

There was a cough at first, but it cleared up before his appointment. And then, last week, a few episodes of vomiting. On Friday he slipped on the stairs and I feared he was hurt, but he rallied and we walked out to the waterfront, a hundred trees marked along the way, squirrels and ducks on high alert. But he lagged on the way back and I complained, stupidly not seeing that this was our last long walk. A day later and he was unable to rise from his bed. The emergency vet found a big lump in his stomach and gave us a list of at-home euthanasia services.

You get used to death by having everyone around you die. With all of two living relatives remaining and a long list of friends gone, I am familiar enough with the process. It is absurd to grieve for a dog the way I never grieved for all of those people, but that’s how it is.

Ken Layne does not usually write about dogs. Photos by Ken Layne and @LCraneMojave.