John Suther looks like someone who appeared from under the bed in a cattle rustler's nightmare. His badge describes him as senior special investigator for California's Bureau of Livestock Identification, but in the parlance of his trade he's known more simply as a stock detective. The job warrants the use of a 4x4 Chevy pickup outfitted with lights and a siren and, on more than a few occasions, a bulletproof tactical vest. Suther's personal jurisdiction measures 250 by 800 miles, or, in other words, the entirety of California. His body size is proportional to the task. He's six-two, 230 pounds, and his small, blue, deep-set eyes leave one in the uncomfortable position of second-guessing the meaning behind the mischievous smiles that he likes to flash from beneath a handlebar mustache and the brim of a beaver-felt cowboy hat.

Suther, 51, was born and raised on a ranch in Northern California. When he's not on the road, which is about half the time, he lives outside of Redding with his wife and son, his horses, and a small herd of cattle. His occupation, which is more like a lifestyle, might seem anachronistic, a throwback to a bygone century when hired gunmen strung cattle rustlers by the neck from cottonwoods and left their bodies to be picked clean by turkey buzzards. But while many of the details of the profession have changed—rustlers are more likely to end up in jail than at the end of a rope, and stock detectives rely as much on DNA and GPS as they do on tracks in the dust—the ancient game of cat and mouse is surprisingly alive and well in today's New West.

That stands to reason, because as long as people insist on taking valuable things that belong to others, there's bound to be someone who makes his living getting those things back—and livestock certainly has a value. There are about 94 million head of cattle in the United States, along with six million sheep and nine million horses. (These three species make up the vast majority of stolen livestock.) That's roughly one animal for every 2.8 Americans, for a total market value of more than $50 billion. Larry Hayhurst, the head of Idaho's livestock-identification agency, put it to me this way: "A truckload of cattle is worth 20 grand. And, hell, people will knock off a 7-Eleven for 50 bucks."

The appeal of livestock theft is that it's often difficult for buyers to differentiate between legitimate and stolen goods. Unlike electronics, which usually fetch only 25 to 50 percent of their actual value when sold to pawnshops or on the black market, hot cattle usually net 100 percent.

John Suther has been a stock detective for more than ten years, and he makes about 15 arrests annually, more than most of the dozens of stock detectives working in the West today. Of these, he's had only two hung juries and not a single acquittal. His investigations have involved a never-ending litany of 21st-century weirdness: thugs stealing dairy calves at knifepoint; a guy hauling stolen and hog-tied calves in the back of a Volkswagen Jetta; organized criminal operations laundering drug money through trade in stolen livestock; illegal immigrants running barbaric underground rodeo circuits; and, in one of the largest cattle scams in American history, a missing $865,000 from one of the highest-paid actors on TV.

Some might say this is the New West, but it comes with an old twist.

IN A ROUNDABOUT WAY, my interest in stock detectives was begat by a childhood experience. When I was a little kid, my uncle Jim suggested that he and my old man raise a pair of hogs. Uncle Jim proposed that my dad put up the money for the piglets and the feed and that he would do all the physical work of raising them on his farm in Illinois. At slaughter time, they'd each walk away with a whole pig for the freezer. The deal progressed through the initial stages. Then one day Uncle Jim called to say that one of the pigs had mysteriously vanished. My old man wasn't terribly upset; after all, he figured, he still had half a hog. However, Uncle Jim explained why that wasn't true.

"The one that got away," said Uncle Jim, "well, that one was your pig."