It is widely assumed that Yellowstone National Park is a year-round sanctuary for wildlife'a landscape that protects animals within park boundaries from human impacts. But the Park alone can neither contain nor sustain many of the wide-ranging species that people generally associate with it. Populations of large mammals, raptors, waterfowl, and many other species require space far beyond park boundaries during at least part of each year, to secure the resources necessary to survive and reproduce. To these creatures, the boundaries of our parks, forests, and ranches are invisible.In this publication and the museum exhibition it accompanies, noted authorities in several fields explore the invisible boundaries of the Greater Yellowstone Ecosystem from diverse perspectives. Eminent conservation biologist Thomas Lovejoy places Greater Yellowstone in a global context, identifying the implications of animal movements for ecosystem conservation in our fragmented world. Ecologist and wildlife biologist Charles Preston reviews the genesis of the Greater Yellowstone Ecosystem concept and how it holds up to our current knowledge of wildlife movements and changing environments inside and outside Yellowstone National Park. Ecologist Arthur Middleton explains why elk and their spectacular annual migrations through the rugged country in and around Yellowstone are ideal vehicles to help us understand the challenges of cross-boundary movements. Wildlife photojournalist Joe Riis takes us along on the journeys of elk and other wildlife through Greater Yellowstone's magnificent backcountry, sharing his ground-breaking photography along with insights from nearly a decade of field work documenting these monumental journeys. Further extending the dialogue, artist James Prosek explores elk and other animal migrations through original artwork, freeing us from scientific and documentary boundaries to consider Yellowstone, conservation, and nature's fluidity from a different plane of human experience. Art historian Karen McWhorter ties everything together with observations and historical perspectives on collaborations among scientists, artists, and photographers toward increasing appreciation and understanding of the complex natural phenomenon of Yellowstone's great animal migrations.