The Western Arctic Herd (WAH) is the largest caribou herd in Alaska and one of the largest in the world. A herd of caribou is defined by the repeated use of discrete calving grounds. The WAH ranges over approximately 140,000 square miles (363,000 km2) of northwestern Alaska. In spring, caribou travel north toward calving grounds and summer range, including the Brooks Range and its northern foothills. During summer, movement is initially westward toward the Lisburne Hills and then switches eastward through the Brooks Range. WAH caribou disperse during the fall as they move south and west toward wintering grounds. The WAH winters in the Nulato Hills as far south as the Unalakleet River drainage and on the eastern half of the Seward Peninsula. The WAH has been hunted for thousands of years and remains an important resource to the subsistence users of Northwest Alaska. Many factors could impact the range, population, and health of the herd, including alterations in climate, industrial developments, and changes in the number of people hunting caribou. For the continued prosperity of the WAH, a collaborative effort between concerned parties is essential in making important decisions regarding the success of the herd.