And everything in their evolution makes wolves want to run, not stay behind fences. Nature has designed them to travel 30 to 50 miles a day; in Idaho, the typical size of a wolf pack's territory — the area where wolves hunt and defend their food sources against rival packs — stretches over 360 square miles. Many captive-wolf owners are frank about the difficulties they face: aggression, repeated escape attempts, self-mutilation. At Wolfwood Refuge & Adoption Center near Ignacio, Colo., owner Paula Watson has reconfigured one wolf's enclosure several times because he scales 10-foot fences with ease. "Matok always wants out," she says. At Eagle Tail Mountain Wolf Sanctuary in Tonapah, Ariz., where Patricia and Kelly Reed care for as many as 120 wolves and wolf-dog hybrids, a wolf shoved his paw through the chainlink separating two pens; the wolves in the adjoining pen chewed it off. In all the commotion and heightened tension, the wounded animal's own pen mates attacked him from behind. Now he hobbles around on three legs, one foreleg having been amputated to the shoulder.

Captive wolves actually demonstrate more violent behavior than wild wolves. Tour guides often refer to the more dominant (read aggressive) captives as "alpha wolves," a largely outdated term coined by animal behaviorist Rudolph Schenkel in the 1940s. Schenkel applied the term "alpha" to winners of the fierce contests for dominance he observed in a group of captive wolves, where only the animals that prevailed — sometimes the survivors of lethal fights — could mate and produce offspring. He assumed that wild wolves lived in a similar system of dominance and forced submission. Renowned wolf biologist L. David Mech, who has extensively studied wolves in the wild, has called the whole alpha concept into question, pointing out that at its core a wild wolf pack is made up of Mom, Dad and kids. Calling a breeding male and female the "alpha pair" makes about as much sense as describing human parents as "alphas." As adults with survival skills and experience, wolf parents are natural leaders, but they don't abuse their offspring physically or psychologically to make them behave. Displays of dominance and submission, as when a wild wolf rolls on its back, are voluntary, not forced, and serve to maintain friendly relations within the pack, much as human social courtesies do. Mech prefers the term "breeding pair" to refer to reproducing members of a wild wolf pack.

Calling a captive group of mostly unrelated animals a "pack" — as many captive-wolf operations do — is misleading in a number of ways. In captivity, wolves can't cooperate to hunt together or disperse to form new packs. As Weber of Mission: Wolf points out: "Throwing a bunch of captive wolves together to observe pack dynamics is like throwing a group of prison inmates together to study family relationships." Wolf handlers sometimes receive the brunt of confinement stress and territoriality, even from bottle-fed, human-socialized wolves — getting nipped or bitten or chased out of enclosures. At Arizona's Eagle Tail Mountain Wolf Sanctuary, Kelly Reed told me that some wolves that have lived at the sanctuary for more than eight years remain unapproachable. "They come to me if they want to," Reed said. "If they don't, I let 'em alone." I watched as some animals paced inside their fences, treading the same pattern over and over, wearing trenches a foot deep in some places.

Some operations try to provide temporary stress relief by bringing in wolf puppies to cheer up captives, exacerbating the long-term problem of too many wolves in captivity. A staff biologist at one of the operations told me, "Adding new life to our exhibit maintains an active, socially cohesive pack and allows the focus of the wolves to be on the newest members of the pack, rather than the oldest members." When I pressed her to elaborate, it turns out she really meant that when old-timers "slip rank" and the younger, stronger wolves harass them, puppies are a great way to alleviate tension — at least for a while. Eventually, the old wolves have to be housed in a separate enclosure just to survive.

And life in an enclosure can last a long time. Take Sabertooth, at the time I met him a 15-year-old "geriatric" wolf living at Mission: Wolf. Already he had lived three times longer than the average wild wolf. His hips were going out, and he had sores on his ears. He was what Weber calls a "lifer," which for a captive wolf could mean 16 years or longer.

It's tempting to think that setting captive wolves free would be kinder. But aside from the political furor that would erupt over any attempt to introduce still more wolves into their native habitats, releasing captives amounts to a death sentence, as biologist Heft explained after Chemukh escaped from WERC. Some wolves would lack a natural wariness of people and be shot as a threat when they drifted too close. And wild wolves, highly territorial animals, would likely see the strange wolves as intruders and kill them. Also, wolf pups learn to hunt from their parents, so former captives would probably lack the skills to hunt large prey like elk and moose; instead, they would likely go after easier targets like livestock.

In 2006, a wolf-like "mystery predator" roaming central Montana killed 120 sheep before federal officials shot it from an airplane and sent the carcass to a wildlife forensics laboratory in Oregon. Dyan Straughan, a forensic scientist specializing in wolf casework, concluded that the rampaging predator had DNA from Wisconsin and Alaskan wolf populations. Although wolves do travel great distances, "that kind of mating just doesn't happen in nature," Straughan said. The animal bit sheep over their entire bodies, hunting instinctively but without the knowledge to kill efficiently. It was probably a captive-bred wolf that had either escaped or been dumped.

To attract paying visitors, even some of the most respected facilities blur the line between conservation and entertainment. They argue that providing some amusement — pettable wolves, wolves with hokey Indian-style names, and "trick wolves" that jump through hoops and balance on teeter-totters — keeps the tourists interested and helps educate them.