Abstract: Historical accounts, park records, and biologists' observations indicated that wintering elk in Yellowstone's northern range were present in low numbers prior to and at park establishment in 1872; increased to 20,000-35,000 by the early 1900s when they heavily impacted the northern-range ecosystem; and declined to 3,172 censused animals in 1968 due to park control efforts. In 1967, the park announced a politically coerced natural-regulation policy terminating park control; and in 1971 posed a natural-regulation ecological hypothesis stating that northern-range elk had been numerous prior to 1872, had not risen to 20,000-35,000 in the early 1900s, and would stabilize at moderate numbers following recovery from control efforts without significantly affecting the northern-range ecosystem. Archaeological and historic evidence, park records, and censuses begun in the 1920s indicate a northern herd of ~5,000-6,000 in 1872, increasing to ~20,000-35,000 in the early 1900s, declining to a censused number of 3,172 in 1968 in response to control efforts, increasing to a census-based number of 21,071-25,920 in the 1980s and 1990s, then declining somewhat after 2000. This book reviews critically the published and unpublished records to test the natural-regulation hypothesis and propose a conceptual model of the northern-range ecosystem with inferences from system changes associated with the four stages of elk abundance, inside-outside exclosure comparisons, and system comparisons inside and outside park boundaries.

Keywords: natural-regulation policy, natural-regulation hypothesis, northern range, elk population, vegetation subsystems, sympatric ungulates, ecosystem processes, ecosystem model, biodiversity, research objectivity