Corridor Ecology: Carnivore Migration Patterns

In the Age of Man many large-carnivore migration patterns have been disrupted. Corridor Ecology allows us to research humankind’s impact on these innate animal behaviors.

Wild Lynx in it's Natural Habitat

“Although the young lynx didn’t know it, in addition to a bulky collar he’d acquired a name: BC03M02. Wildlife managers and scientist had moved him to the United States for a lynx reintroduction program.”

Photo by Fotolia/Marcel Schauer

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What would it be like to live in a world with no predators roaming our landscapes? In The Carnivore Way, (Island Press, 2014), author Cristina Eisenberg argues compellingly for the necessity of top predators in large, undisturbed landscapes, and how a continental-long corridor – a “Carnivore Way” – provides the room they need to roam. This excerpt examines the current migration patterns of these large carnivores and the impact that industrialized North America has had on them.

In early 2003, a two-year-old male lynx (Lynx canadensis) was cruising through his territory near Kamloops, British Columbia, searching for prey. As he maneuvered through the forest, padding easily in deep snow, he picked up the scent of food. He lowered his nose, took a step, and paused. All at once, what should have been just another in a lifetime of simple steps proved ill-fated. He found himself caught. No matter what he did, he couldn’t free his paw from the hold of a trap. Soon a human came along and jabbed something sharp in his rump, which rendered him unable to move. When he came back to his senses, his life had changed in surprising ways.

Although the young lynx didn’t know it, in addition to a bulky collar he’d acquired a name: BC03M02. Wildlife managers and scientist had moved him to the United States for a lynx reintroduction program. Eventually he was released into southern Colorado’s high country. It was much drier there than in his northern Rocky Mountain home where he was born, and there weren’t as many snowshoe hares (Lepus americanus), his favorite prey. But he found a willing, fecund mate and enough to eat. Life was good; in two years he sired three litters of kittens. And then one day in late 2006, something in his brain, some inchoate longing, some homing instinct, made him feel like roaming. At first he simply traveled from one snowshoe hare stronghold to another, finding food when he needed it. After a while he started ranging farther, and eventually just kept going. He ended up crossing landscapes unlike any he’d experienced before: the Wyoming Red Desert, followed by the Greater Yellowstone Ecosystem.

Colorado Parks and Wildlife (CPW) biologists determined that over the next several months the lynx covered 2,000 miles. His last recorded collar signal before the battery gave out occurred in late April 2007. Eventually BC03M02 found his way remarkably close to where he was born, near Banff National Park, Alberta. And there his life ended, in another trapline—a lethal one set to legally harvest fur-bearing mammals. Superbly healthy at the time of his death, wellfed, with a luxuriant coat of fur, he set a world record for the greatest known distance traveled by one of his kind. Despite his tragic end, BC03M02 proved that even in our fractured world, it’s possible for a carnivore to roam widely. But ultimately, the media hoopla about how far he’d traveled belied the tragedy of his death.

In recent years, lynx from the CPW reintroduction project also have dispersed south, into New Mexico’s mountains. Researchers didn’t anticipate these dispersals, which involved crossing interstate highways, traversing areas of high human use, and dodging death in myriad ways. En route, these dispersers had to find snowshoe hares to eat—not always an easy task.

Other species besides lynx have an innate need to wander. These instinctive journeys involve both migration, defined as seasonal, cyclical movements from one region to another and back for breeding and feeding purposes, and also dispersal, the process animals use to leave their natal range and spread permanently from one place to another. Many species, such as pronghorn (Antilocapra americana) and elk (Cervus elaphus), migrate as part of their annual life cycle. Fewer species disperse. Wolves (Canis lupus), wolverines (Gulo gulo), cougars (Puma concolor), jaguars (Panthera onca), lynx, and grizzy bears (Ursus arctos) have natural histories that often include long dispersals (although grizzly bears don’t disperse as far as some of these other carnivore species).

In our developed world, landscape-scale dispersals are becoming increasingly challenging for all species, but they are still happening. In February 2008 in California’s Tahoe National Forest, while being used to conduct a marten study (Martes americana), Oregon State University graduate student Katie Moriarty’s remote-sensing camera photographed what appeared to be a wolverine. California’s first substantiated wolverine sighting since the 1920s, the grainy image created a furor. Scientists began by trying to figure out where it had come from. The nearest known population was about 900 miles away, in Washington State. DNA tests of scat samples collected from the animal proved that it was genetically related to Rocky Mountain wolverines and had dispersed from an out-of-state population.

In spring 2009, a two-year-old female Yellowstone wolf wearing an Argos satellite collar made an astonishing, 1,000-mile trek to north-central Colorado. Aspen-crowned mountains and deep valleys in that part of Colorado harbor abundant food for wolves: healthy deer (Odocoileus hemionus) and elk herds. However, it’s not very safe to be a wolf in Colorado, due to low human tolerance for this species as well as other hazards. This wolf hung around Eagle County for a few weeks, but eventually died after eating poison intended for coyotes (Canis latrans).

One of the most compelling long-distance dispersals began in Oregon in September 2011, when a young male wolf left northeast Oregon’s Imnaha pack. Called OR7 by the Oregon Division of Fish and Wildlife (ODFW), he covered an astonishing range of territory through the state as he moved toward the southern Cascade Mountains. ODFW began posting images of his walkabout, which showed up on their maps as a thick, black zigzagging line. Popularly dubbed Journey, this wolf drew public attention as he wandered around Oregon in search of a mate. Often he looped and doubled back on himself, but each week he trended farther south. Just before Christmas 2011, he reached Crater Lake.

After Christmas, a public question arose: how far south would this vagabond wolf go? Some wondered whether he was looking for love in all the wrong places. Right before New Year’s Eve, the public got their answer to the first question. Journey entered California, becoming the first wolf confirmed in the state since 1924. For the next fifteen months he stayed in Northern California and out of trouble. He preyed on deer and left cattle alone, but didn’t find a mate. In mid-March 2013 he returned to southwest Oregon, where he remained through the end of that year. His California travels inspired the state legislature and Game Commission to consider putting the wolf on the state list of threatened and endangered plants and animals, and to begin creating a management plan for this species.

These transboundary stories make our hearts beat a little faster and give rise to complex emotions: wonder, grief, hope. How many other such dispersals of which we are unaware have there been? Why do so many have tragic endings? And how can we improve the outcomes, now that we’re aware that these dispersals do occur?

Audacious as such dispersals may seem, some animals can’t help making them. This behavior is imprinted in their DNA, in the shape of their bodies, and in how their minds work. Moreover, they do it with casual grace, as if such heroic dispersals amounted to just another day in their lives. There goes a wolf, loping a thousand miles in a harmonic, energy-conserving gait, its hind feet falling perfectly into the tracks left by its front feet. And a wolverine, effortlessly running up mountains and back down in minutes, covering more ground and elevation more rapidly than any other terrestrial mammal. If such behavior were a simple act of will, most of these stories would have happy endings. But nevertheless, these dispersals fill me with hope that perhaps we’ll soon get it right, given the opportunities and powerful lessons these animals are providing.

The corridor that the carnivores use for dispersal in the West extends from Alaska to Mexico. It holds many stories and goes by various names. Long ago, the Blackfeet called it miistakis—the backbone of the world. The conservation organization Wildlands Network refers to this cordillera as the Spine of the Continent. And I call this pathway worn into our continent by carnivore footfalls across the ages The Carnivore Way. The illustration in The Slideshow depicts the Carnivore Way and the 2013 distribution of the six large carnivore species (grizzly bear, wolf, wolverine, lynx, cougar, jaguar) I write about that live within this corridor.

When I found our wild Montana home, I made a dispersal of my own that taught me to think about conservation on a landscape scale. My earliest lessons in our new home had to do with learning about the Crown of the Continent Ecosystem, arguably one of the most intact ecosystems south of Alaska. Getting to know this vast landscape, where mountains and public lands stretch from horizon to horizon, sparked my interest in corridor ecology—the science of how animals move across landscapes and inhabit them. I wanted to better understand the conservation requirements of animals that need to cover a lot of ground in order to thrive, and what people can do to create healthier, more connected landscapes for them.

The Backbone of the World

Our home lies roughly at the center of the Crown of the Continent Ecosystem, which contains some very big country. This 28-million-acre ecosystem extends east to where the Great Plains meet the Rocky Mountains, south to Montana’s Blackfoot River Valley, west to the Salish Mountains, and north to Alberta’s Highwood Pass. The Continental Divide splits it north to south. Its jumbled terrain contains a crazy quilt of mountains: the Livingstone, Mission, and Whitefish ranges, among many others. Watersheds best characterize this ecosystem: the Elk, Flathead, Belly River, and Blackfoot. It contains a triple-divide peak from which rainfall flows into the Pacific, Arctic, and Atlantic oceans, and there are thousands of lakes of glacial origin. But anyone who has spent time here knows that the Crown of the Continent, its wildness seemingly endless, is far more than the sum of its parts.

The large carnivores are part of what makes this place so ecologically remarkable.

One of the two ecosystems in the 48 contiguous United States that contain all the wildlife species present at the time of the Lewis and Clark Expedition (1804–6), the Crown of the Continent provides critical habitat for animals that need room to roam. John Weaver, senior scientist for the Wildlife Conservation Society (WCS), has found seventeen carnivore species here, a number unmatched elsewhere in North America, including the Greater Yellowstone Ecosystem and Alaska.

According to Weaver, the Crown of the Continent matters for three principal reasons. First, because of its large, intact wildlands that provide more habitat security for carnivores than do other ecosystems with greater human development. Second, because of its connection to northern ecosystems with abundant large carnivores. Third, because of its physical and biological diversity. The Crown of the Continent has four climatic influences: Pacific Maritime in the west, prairie in the east, boreal in the north, and Great Basin in the southwest. Coupled with a tremendous range of elevation from prairie to peak, these influences create a variety of environmental conditions which, in turn, support a variety of ecological communities, from shortgrass prairie to old-growth rainforest.

Within this ecosystem, rivers have incised narrow, fertile valleys into the mountains. These valleys—one of which I live in—represent the last bastions of wildness, where a grizzly bear can travel easily, finding abundant food and little trace of humanity. Yet even in a place as wild as this, much is at stake, because human encroachment places a great deal of stress on large carnivore habitat. For example, some of these animals are having their travel corridors cut off by logging, natural gas extraction, and backcountry recreation (e.g., the use of snowmobiles).

In the mid-2000s, I began doing research on wolves in Waterton-Glacier International Peace Park, which lies in the core of the Crown of the Continent. This peace park is composed of two national parks: Glacier National Park in the United States and Waterton Lakes National Park in Canada. Glacier, established in 1910 at the urging of New York naturalist George Bird Grinnell, comprises 1 million acres. Waterton, established in 1895 as a forest preserve, comprises 124,000 acres contiguous to Glacier. One hundred and seventy such peace parks exist worldwide, but Waterton-Glacier was the first. Dedicated to protecting biodiversity and natural and cultural resources, peace parks help maintain connectivity across boundaries. In 1995, the United Nations designated Waterton-Glacier a World Heritage Site.

A closer look reveals why this is a critical linking landscape. At Logan Pass, the highest pass in Glacier accessible by car, the millions of visitors who stop here annually see protected lands stretching out in every direction. The hundreds of peaks all around make it obvious why the Blackfeet consider this the world’s backbone. Yet this area’s wildness is not quite as big as it seems. Twenty miles away, the Blackfeet Reservation, which consists mainly of working ranches, forms Glacier’s eastern boundary. The tribe has been fighting extensive natural gas exploration on their land, although various factions within the tribal community have differing opinions and interests.

Waterton-Glacier contains two principal wildlife corridors: the Flathead Valley and the Belly River Valley. Both cross international boundaries. The first begins in southeast British Columbia, where the Flathead River flows south across the border into northwest Montana, forming the western boundary of Glacier National Park. This watershed provides an essential corridor for everything from grizzly bears and wolves to native westslope cutthroat trout (Oncorhynchus clarkii lewisi). Bull trout (Salvelinus confluentus) here make a dramatic 150-mile spawning journey from their Flathead Lake winter waters northward to their autumn spawning sites in the headwaters of the Canadian Flathead. But because this corridor contains rich deposits of coal, minerals, and coalbed gas, the potential for ecological damage by extracting these resources (e.g., mining and gas exploration that includes hydraulic fracturing, or “fracking”) threatens the health of this corridor and its watershed. To keep it healthy and to protect its wild character from development, many people, including Canadian conservationist Harvey Locke and WCS senior scientist John Weaver, have been recommending expanding Waterton Lakes National Park into British Columbia.

The second major corridor, the Belly River Valley, begins at the feet of Chief Mountain. This 9,000-foot massif, sacred to the Blackfeet, stands in Glacier near the US-Canada border. From its headwaters, the Belly River flows northward into Canada, lending its name to the valley it carved out of limestone. One of the wildest places in the region, this valley was popular for trapping wolves, grizzly bears, wolverines, lynx, and cougars during the nineteenth-century furtrading era. However, by the 1920s these and other fur-bearing mammals had been trapped out of existence. Later in the twentieth century, when these species gained protection in the United States and in the Canadian national parks, the Belly River Valley became one of the first places they returned. At the Chief Mountain port of entry, a granite obelisk and narrow clearcut demarcate the border crossing and provide a strong reminder that legal boundaries, however invisible to the large carnivores who cross them regularly, are very real in terms of land management.

In Waterton Lakes National Park, the mountains abruptly meet the prairie, with no foothills to soften this knife-edged transition. A bunchgrass and wildflower sea slams into a wall of mountains. Waterton, small as it is (124,000 acres), represents an invaluable refuge for carnivores. The landscape that extends north along the Rocky Mountains past Waterton, toward the Kananaskis provincial wildland and Banff National Park, connects US populations of farranging species, such as grizzlies, to Canadian populations, helping to ensure their long-term survival. This connectivity makes the Crown of the Continent unique. In contrast, Yellowstone is an ecological island because human development has cut off many of its carnivores from other populations.

Immediately north of the US-Canada border, most large carnivore species are managed with scant (but growing) recognition of their contribution to ternational conservation. Beyond national parks, humans can kill most large carnivore species via hunting and trapping. To use wolves as an example, in Alberta, a landowner is entitled to shoot a wolf at any time of year and without a license within five miles of his or her private property or grazing-leased public land. The government permits baiting wolves with poison. Some Alberta townships still offer a wolf bounty. Despite all of the above, Alberta has a varying, but well-established wolf population, with several packs ranging along the East Slope of the Rocky Mountains, from Banff to the US-Canada border.

Waterton ecologist Barb Johnston has spent decades working with wildlife in this and other national parks, such as Banff, which is 1.6 million acres in size. When I asked her why a park as small as Waterton, which lies at the other end of the size spectrum from Banff, is so important to landscape-scale conservation she said, “Usually when you talk about carnivores, the main theme is large, undeveloped space that they can roam in. Waterton doesn’t fall into that category, because it is so tiny. But because it is positioned where it is, we are part of a travel corridor for carnivores. Waterton is adjacent to source populations for carnivores, particularly grizzly bears and wolves, but also wolverines. We are a critical linking land, because we are also adjacent to what makes population sinks for species that don’t do so well in human-dominated areas.”

Outside Waterton, wilderness meets the Anthropocene. Coined by ecologist Eugene Stoermer in the 1980s, but popularized by Dutch chemist Paul Crutzen in 2002, the term Anthropocene refers to the geological epoch that began with the Industrial Revolution in the late seventeenth century. Ranchlands, developed over a century ago for cattle production, bound Waterton to the east. And 200 miles north lies Calgary, one of Canada’s largest cities. Banff National Park, the most visited Canadian park, lies 65 miles west of Calgary, along Highway 1. This four-lane road, also known as the Trans-Canada Highway, slices through the heart of Banff via the Bow Valley. Completed in 1965 to connect the Canadian interior to the West Coast, this originally low-volume, two-lane highway once had little impact on wildlife. In 1950 Calgary had 130,000 people; by 2011 it had over 1 million. Also by 2011, approximately 30,000 vehicles passed through the Bow Valley daily. Such human impacts, which bring with them an accelerated extinction rate, typify the Anthropocene—the Age of Man.


From The Carnivore Way by Christina Eisenberg. Copyright © 2014 Christina Eisenberg. Reproduced by permission of Island Press, Washington, D.C.