One of the last great wildernesses in the contiguous United States is located in the southeastern corner of Yellowstone National Park. This area, anchored by the Thorofare region, is farther from a road than any other spot in the continental U.S. Those who have traveled to the Thorofare know its grandeur, its mountains, its animals, its wildness. But for most of the twentieth century, few, if any, wolves traveled this vast landscape. The area’s apex carnivore had been eradicated as part of a larger predator control campaign many decades ago. Was the Thorofare really wild, when what some consider the defining feature of North American wildness was absent? Many who have experienced wolf country feel it is like no other. Some believe that wolves make all the difference, and if you’re open to it, you can feel the aura of wildness so intensely, it makes all other country seem dull.

Since the summer of 2001, visitors to the Thorofare area have reported hearing wolf howls virtually every night. Around dusk, when the calmness of evening sets in, the wolves let loose. From the depths of this great immensity, their ancient song rings out with amazing regularity. Canoeists and kayakers paddling across Yellowstone Lake from the north, backpackers and horseback riders coming from all directions—people hear the wolves. For some, this presence represents progress. Thorofare has recovered from an age-old wound, and this remote place has withdrawn a little farther away from civilization again.

Those echoing howls are not limited to Thorofare, but are now heard throughout the Greater Yellowstone Ecosystem (GYE). The effort to restore the howl took decades, involved many people, and culminated in the reintroduction of wolves to Yellowstone National Park in 1995 and 1996. The story of that restoration is unique and represents an important effort to restore Yellowstone National Park to its natural conditions, a long-stated goal of the National Park Service. With the reintroduction of wolves to the landscape, one of the last great ecosystems on the planet is changing right before our eyes—an unprecedented opportunity for observation and research.

Predator Control and the Endangered Species Act

In many ways, wolves have been pawns in a larger cultural and philosophical battle. The last known wolf in Yellowstone National Park was killed in Lamar Valley in 1926. At that time, Congress sanctioned predator control in the park, and most people agreed with it. (Bears, though, were spared because of their contributions to visitor enjoyment and because most people, including park staff, didn’t consider them predatory to any significant extent.) In part, predator eradication was "how the West was won"; the range was made suitable for livestock through predator removal.

The National Park Service ended the systematic killing of predators in 1933, but it wasn’t until 1973 that Congress passed the Endangered Species Act (ESA), making restoration of endangered species to suitable habitat the law. This was a policy reversal for the federal government, from sanctioned eradication to restoration. The Rocky Mountain wolf (Canis lupus irremotus) was listed as endangered under this act in 1973, and in 1978 the entire species Canis lupus was listed as endangered in the lower 48 United States, except in Minnesota. The ESA was evidence that times were changing. Public tolerance for predator control was waning. Wolf restoration has, in large part, been about this change in attitudes. The future of wolves will depend on the same.

In 1980, the first U.S. Fish and Wildlife Service (USFWS) Northern Rocky Mountain Wolf Recovery Plan was signed, and it was updated in 1987. The goal was 30 breeding pairs for three successive years in three designated areas of Idaho, Montana, and Wyoming. Northwest Montana already had wolves through natural immigration from the Canadian Rockies, so the strategy was to nurture wolf populations there through protection and reintroduce wolves from Canada to Idaho and Yellowstone. Upon achievement of the recovery goals, wolves would be removed from the endangered species list and turned over to the respective states for management, assuming that the states had federally-approved management plans in place.

In 1988, Congress directed the NPS to study the potential impacts of wolf reintroduction to Yellowstone. The Wolves for Yellowstone? A Report to the U.S. Congress studies were published in 1990. In 1991, Congress finally authorized funds and directed the USFWS, in consultation with the NPS and the U.S. Forest Service, to develop an Environmental Impact Statement on wolf reintroduction to Yellowstone National Park and central Idaho. The EIS was signed in June 1994, officially endorsing the restoration of wolves to Yellowstone.

In October 1994, Michael K. Phillips arrived in the park to be the leader of the Yellowstone Gray Wolf Restoration Project, a position he held until May 1997, when the reintroduction phase of the wolf recovery program was complete and a monitoring plan was in place. Phillips then accepted a job with Turner Enterprises in Gallatin Gateway, Montana, where he still works as the Executive Director of the Turner Endangered Species Fund. At that time, I stepped up from wolf biologist under Phillips to Wolf Project Leader. Prior to his work in Yellowstone, Phillips was the coordinator of field projects for the Red Wolf Recovery Program in the southeastern United States. That program successfully restored the red wolf to parts of its former range. Phillips was also involved in another successful wolf reintroduction program after he left Yellowstone: the USFWS’s reintroduction of Mexican wolves to southeastern Arizona and southwestern New Mexico. Along with Yellowstone’s program, these are the other main successful wolf reintroduction projects yet attempted.

Wolf Reintroduction

By 1995, more than 20 years after listing, wolf reintroduction was ready to begin. This is not to say the battle over wolves subsided. Despite some strong opposition, primarily from the local ranching and political communities, the USFWS and Canadian wildlife biologists captured a total of 31 Canadian wolves by darting them from a helicopter and shipped them to Yellowstone. Fourteen came from Alberta in January 1995, and 17 from British Columbia in January 1996. An additional 35 wolves from the same locations were shipped to central Idaho’s Frank Church—River of No Return Wilderness. The Canadian source areas, situated along the Rocky Mountains, were similar to Yellowstone in terrain and prey type. In addition to the Canadian wolves, 10 wolf pups from northwest Montana (caught after their parents were killed in a control action due to livestock depredation) were released in Yellowstone in late winter 1997. The reintroduction of these pups was not very successful, as they spent the winter in a pen rather than learning in the wild. They were also released after one of the most severe winters on record, which made hunting for ungulates difficult; eight of the 10 were dead within four months. As of late 2004, the other two were still alive as part of the Nez Perce pack.

Release strategies differed between Yellowstone and Idaho. In Yellowstone, wolves were acclimated as family groups (packs) in pens and "soft" released; in Idaho, the USFWS "hard" released wolves, as individuals, directly onto the landscape. Part of the reason for the different techniques was the disparate nature of the recovery areas. The areas of Yellowstone where the wolves were released were less remote than those of central Idaho, so the wolves had less room to safely wander after release. The area where wolves were released in Idaho allowed more wide-ranging movements. In Yellowstone, acclimation was chosen because it has been known to curtail wolf movements and break their homing instinct. The Yellowstone road system and availability of park staff also made acclimation pens accessible, and therefore more feasible than in Idaho.

In 1995, the first three groups of wolves were placed in pens on Yellowstone’s northern range at Soda Butte, Rose Creek, and Crystal Creek. In 1996, four groups were placed in pens, two of which were not on the northern range: one at Nez Perce Creek, and one on the southeast arm of Yellowstone Lake. In each pen was a group of wolves caught together in Canada. When a breeding pair could not be captured, Yellowstone Wolf Project staff "match-made" a pair in the pen, creating a pack. An adult male and female in a pen will almost always get along, and adding pups of either sex rarely causes problems. Introducing same-sexed adult wolves in pens, however, almost always causes fights or deaths. The Rose Creek pack, led by #9 and #10, was an example of a match-made pack; the Druid Peak and Lone Star packs were others.

The wolves were held 10 weeks, a period of time that Yellowstone National Park biologists estimated would be adequate for acclimation. Over two winters, Wolf Project and other park staff visited the 41 penned wolves minimally—twice a week to feed them road-killed deer, elk, moose, and bison. This allowed us to learn their characteristics and personalities well, which facilitated identification after release—a rare and relishable opportunity for wild wolf studies. Rangers patrolled the pens continuously from afar, yet close enough to protect the wolves from ill-willed human intent.

Wolf researchers traditionally name wolf packs for geographic features near where they live. Because these wolves didn’t live anywhere yet, Wolf Project staff named them after their pen sites. Since then, wolf packs have sometimes been named to commemorate someone important to wolf reintroduction. Pack names change when a pack no longer lives near the area after which it was named and all of the original members are dead. We numbered and radio collared all the wolves so we could identify individuals for study and management, but we did not give individual animals official names. Some have criticized us for this decision, but we did not want to humanize the wolves. Grizzly bears in Yellowstone are not named for the same reason. Some people informally name certain bears and wolves anyway, but apart from their collars, the wolves were autonomous from humans after release, except in extraordinary circumstances.

Release from the Pens

No one knew what would happen when we opened the gates to the pens. We assumed the wolves would run out immediately once they glimpsed freedom; people speculated on how far they would go before they stopped running. Cartoons in local newspapers had them "making a run for the border."

That did not happen. A video camera mounted in a tree at the Crystal Creek pen ran for about an hour when that pack was released. The alpha female, #5, approached and looked out the wide-open door six times in about 20 minutes, but never got close to it. The other wolves avoided the door. It took 10 days for the Crystal wolves to finally leave, but in the meantime, they snuck out at night, explored, and then slipped back in during the day. The Druid Peak pack, probably the best-known pack today, took the longest to leave—12 days—even though we opened two opposite sides of the pen.

The Soda Butte pack left the pen when the gate was opened, but only far enough to chew through the ropes on two deer carcasses that Wolf Project staff had tied to a tree. Then they dragged the carcasses back into the pen. This reluctance to leave the pens was surprising, but we designed subsequent releases so that the wolves would leave the pens when we were absent, thereby eliminating the added stress of human presence and possibly deterring widespread post-release movements.

However, part of the Nez Perce pack left immediately, as #27, the instigator of this rapid departure and of many other wide-ranging movements for her pack, took off with her three daughters. They fled at a pace that was blistering even by wolf standards. From near Old Faithful they traveled to Red Lodge, Montana, via a circuitous route in a few nights. At Red Lodge, the three siblings had had enough and quit following their mother. Either Interstate 90, near Reed Point, Montana, or the new litter to which #27 gave birth finally caused her to stop; she denned alone near Nye, Montana. This settled her down only briefly. Our unsuccessful attempts ro capture #27 and her new litter in order to relocate them to Yellowstone had them on the move as soon as the pups were able.

A year later, USDA Wildlife Services killed #27 after she preyed on livestock near Dillon, Montana, west of the park. This brought an end to a wolf whose wide-ranging movements were what many researchers had expected would characterize the reintroduction of wolves to Yellowstone. Three (#26, #29, and #30) of the four yearlings released from the Nez Perce pen survived to form new packs, breed, and contribute to the restoration. Wolf Project and USDA Wildlife Services staff captured wolf #48, the last surviving pup from the Nye litter, near Nye in February 1997 and relocated her to Yellowstone, where she is now the alpha female of the Nez Perce pack.

Number 27’s mate, #28, and a male pup stayed in the pen until the day after we opened the gate, a delay that prevented the pack from reuniting. They attempted to follow #27’s scent trail, but stalled, then split up. Number 28 wandered widely for about eight months and was later found dead from a gunshot wound, floating in the Madison River near Three Forks, Montana.

The Rose Creek pack also wandered widely. Initially, the pack was made up of three wolves; #9 and her daughter, #7, were introduced to male #10 in the pen. But upon release, #7 traveled alone until January 1996, when she joined a lone male from the Crystal Creek pack, #2. This was the start of the Leopold pack, the first naturally forming wolf pack in Yellowstone’s new wolf era. The name Leopold was used to commemorate the late conservationist Aldo Leopold, who suggested in 1944 that wolves be conserved in Yellowstone.

The Rose Creek pair traveled widely and eventually had a litter near Red Lodge. Around this time, #10 was shot by Red Lodge resident Chad McKittrick, who was convicted of killing a threatened species and possessing and transporting its remains. Number 10’s death precipitated the USFWS’s decision to capture #9 and her litter, as it is rare for a female to raise pups alone, especially in unfamiliar country, and the pups represented 40 percent of the Yellowstone wolf population at the time. Wolf Project staff transported the wolves to the Rose Creek pen, where they remained until the pups could contribute to their own survival. This gave the Rose Creek pack a new start and led to #9’s pairing with another Crystal Creek disperser, #8, who helped raise #9’s eight pups.

We varied the release strategy as we learned from the wolves, modifying as the program continued. Several packs were acclimated at one site, and then moved to another for release (e.g., the Chief Joseph and Lone Star packs). Female #36 was released near Lone Star Geyser Basin, the location of some of the hottest springs in the park, in what appeared to be a successful release. However, shortly after she left the pen, she was scalded in a hot spring and did not recover. It took her 10 days to die, and at the time we were unaware of what had happened because her mate was in the area with her every time we located them, so we did not intervene.

The plan to restore wolves to the GYE via pen acclimation worked. Except for the Nez Perce pack, the goals of acclimation—to reduce post-release movements and maintain familial ties between wolves—were achieved. The plan called for three to five years of Canadian wolf releases, yet only two years were needed in Yellowstone and Idaho. There was some debate over whether even a second year of reintroductions was necessary, but to increase genetic diversity, wolves were brought from Canada a second year. At this point, one of the favorite "sound-bites" of the project popped up: we were "ahead of schedule and under budget." Everyone liked that.

In retrospect, even the Nez Perce releases could be characterized as successful, because the pack’s disintegration produced roaming wolves that paired with other lone wolves and formed new packs. Number 29 started the Gros Ventre pack, #26 the Washakie pack, and #30 the Thorofare pack. Including reproduction from the original Nez Perce pack, these wolves produced seven litters of pups—a significant contribution to wolf restoration in the GYE.

As it turned out, territorial expansion outside the park, such as that of the Nez Perce pack, played a role in how wolf monitoring and management is handled by the agencies cooperating in wolf reintroduction. The U.S. Fish and Wildlife Service was the lead agency for wolf reintroduction, no matter where wolves traveled or settled. Yellowstone National Park hired two people to monitor and manage wolves inside the park, but when wolves left the park early on, there was no nearby USFWS staff to track them. So from 1995 through early 1999, Wolf Project staff followed wolves wherever they went. We made numerous trips to Red Lodge, Jackson, Dillon, Sunlight Basin, and most often, Paradise Valley. In 1999, the USFWS hired new staff and partnered with the Turner Endangered Species Fund and, later, the states of Montana and Idaho, to expand its operations into the GYE outside the park. Yellowstone National Park staff no longer monitor or help manage wolves outside the park.

Territoriality and Population Expansion

Wolves are territorial mammals that establish firm boundaries that they defend against other wolves. A family of wolves, a pack, which is the basic structure of wolf society, defends these territories. Few other mammals live and operate in such a way. Many mammals are solitary, and a group typically consists of a female with young, not an extended family. Numerous factors combine to determine how packs are organized and how big they get. One factor is the size of their primary prey—the larger the prey, the more food is available to eat, which leads to slightly larger packs. Wolves that live on deer tend to have packs of five to seven wolves, whereas wolves that prey on moose or bison tend to have packs of more than 15 wolves. In Yellowstone, with wolves primarily feeding on mid-sized elk, the average pack size during the first 10 years has been 11 wolves, but the range of pack sizes was 2-37.

Wolf pack composition is another factor that guides how packs operate and territories are defended. Simple packs are made up of a breeding pair with pups; a complex pack is a breeding pair with several generations of offspring. In complex packs, the experience level of the wolves is high. Sometimes, in addition to the breeding wolves, there are yearlings as well as two- or three-year-old wolves in the pack. In this case, not every task undertaken by the pack has to be accomplished by the breeders or dominant wolves (historically, these wolves have been referred to as the alphas). Older, subordinate wolves are very capable of contributing their effort. For example, when a pack with breeders and pups attempts to bring down an elk, the adult wolves have to do all the work, as the pups know nothing about this very risky job. In a complex pack, several animals possess this knowledge, so achieving the kill is not completely up to the breeding wolves. We have seen cases where the best hunter is a non-breeding subordinate: wolf # 106, when she lived in the Druid Peak pack, was a prime example.

Most wolf packs in North America are probably simple packs—breeders or alphas with pups. This is due to the unstable nature of wolf packs in environments where humans kill wolves. The vast majority of wolf packs in North America are in Canada and Alaska, where wolves are hunted. In some cases, they are hunted very hard, which results in packs that break apart, preventing them from retaining older wolves and accumulating experience.

Unlike other packs in North America, most Yellowstone packs are complex and very stable. Six packs that formed in 1995 and 1996 still exist: Crystal Creek (now called Mollie’s, after the late Director of the USFWS, Mollie Beattie), Delta, Rose Creek, Druid Peak, Leopold, and Chief Joseph. As of late 2004, 17 of the 19 packs that had formed in the park were extant. This stability and structure has important implications for how wolves operate in the Yellowstone area and in their own packs. Wolf Project staff have been able to detect some of the differences as the structure of packs has matured from simple to complex. In simple packs, the alpha wolves dominate leadership decisions (when to travel, where to go, what to hunt, who hunts). In complex packs, it is less clear who is calling the shots, as many wolves participate in pack activities. This makes the decision-makers harder to identify.

In the beginning, Yellowstone’s mostly simple wolf packs established territories relatively rapidly after release, but there was some confusion and conflict as they divided land among them. When the Druid Peak pack was released in 1996, they had no territory, but they had a territorial mentality, having come from British Columbia where wolves fiercely contest their space. The Druids roamed the landscape, engaging in fights with two other packs that resulted in two wolf fatalities and at least two other injuries. They eventually evicted the Crystal Creek wolves from their territory in Lamar Valley, an event that has had long-term consequences. The Druid Peak wolves still reside in Lamar Valley, while the Crystal Creek pack fled to Pelican Valley, in the middle of the park, where they still reside and were renamed Mollie’s pack.

Following these early—and not unexpected—skirmishes, established territories were quickly defined. They varied greatly in size, ranging from a tiny 53 square miles (Cougar Creek) to a gigantic 553 square miles (Chief Joseph). Packs occupying the prey-rich northern range tended to have smaller territories (average = 113 square miles), while packs where prey was less abundant had larger territories (average = 340 square miles). Such disparity makes it hard to estimate an "average" pack territory. Some of the variability is probably also due to the migratory behavior of seven of the eight elk herds that use the park. Most elk leave the park in the winter, strongly affecting wolf movements and territory size.

Mollie’s pack ranges widely in winter, following major elk migrations, but not in summer, when Pelican Valley is a paradise for wolves. The elk-less winters (almost all elk migrate out of Pelican Valley) force the wolves to either leave the park in search of elk or prey upon bison, which are far more dangerous for wolves to kill. As soon as elk move because of accumulating snow, usually around early December, Mollie’s pack moves too. While their departure is predictable, their direction is not: they have been detected in Hayden Valley, the North Fork of the Shoshone River, and the east side of Yellowstone Lake searching for prey. Some bison remain in Pelican Valley, where they tend to be invulnerable to wolf attack in early winter. In late winter, though, Mollie’s pack returns from its wanderings and focuses on the winter-weakened bison. Epic battles can ensue, with both bison and wolves suffering casualties. The wolves kill enough bison to last them until spring, when elk migrate back into the valley.

The Soda Butte pack (now called the Yellowstone Delta pack) and the Chief Joseph pack also travel widely in winter, following migrating elk. The Nez Perce wolves have begun wandering during the last few winters, as have the Druid Peak wolves on occasion—always around the time when elk migrate from summer to winter ranges. These wanderings have produced clashes between resident and trespassing packs. One Druid wolf (#253) still limps from such an encounter.

The Bechler region was one of the last places in the park to be reoccupied by a pack of wolves. Because typically harsh winters prevent year-round occupation by elk or moose, wolves have had trouble living there. Four wolves were found in Bechler, however, during the summer of 2002, and have remained there during the last two mild winters. A return to harsher winters may move these wolves out of the park in search of migratory prey. Another tough place in the park for wolves to establish a year-round territory is the Mirror Plateau, although they do use it in the summer when elk are at high elevations.

Since they drove out the Crystal Creek pack, the Druid wolves have aggressively maintained their territory in Lamar by killing four more interlopers and wounding several others. Eventually, they killed their own alpha female, #40. Their numbers and strength have dwindled, and long-time alphas #21 and #42 have died, so the pack’s future is uncertain, but Lamar Valley will continue to be a wolf stronghold because of its rich prey. As of this writing, the Slough Creek pack has made significant overtures into Druid territory in a possible takeover of the Lamar.

Excerpted from Yellowstone Science, 13 (1), Winter 2005
Reprinted with permission of the author

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