Reports of starvation and the much-reduced deer population spread around the country in both scientific and popular literature. In the decade leading up to this dramatic climax, few observers commented specifically on the many factors that contributed to the changing fortunes of the deer. Once the crisis became well-known, many commentators focused on the possible role of predatory animals. Critics of systematic predator control immediately drew conclusions from the sequence of events that began with protection of deer from predators. Hindsight made this example of the disruption of the "balance of nature" painfully obvious to some. For others, including those scientists who had seen conditions on the Kaibab firsthand, such suggestions about the relationship between predators and deer seemed quite tentative. Few of them, in fact, suggested ending predator control. Everyone still wanted a wildlife preserve; unrestrained predators might make matters worse by killing the deer that survived starvation. Climate, habitat, and livestock grazing undoubtedly contributed to the problem, but the furor over predators captured all the attention.

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Interpretations of the Story

At this point, the necessary facts to illustrate the lesson of the Kaibab were all in place. The story had reached its climax, even if the eventual fate of the deer remained unknown. Later accounts of the lesson ended with starving deer. Aldo Leopold later wrote that "just as a deer herd lives in mortal fear of its wolves, so does a mountain live in mortal fear of its deer" (Leopold, 1949). This statement summarized an ecological principle concerning predator-prey relationships that became widely-recognized. When humans remove predators from an ecosystem, deer or some equivalent prey species will overrun mountains and rangelands (and more recently, suburban areas). Textbook accounts provided a quick denouement to the Kaibab case that pointed to the stabilization of the population.

One widely-used biology textbook stated, "Thereafter the deer population continued to decline more slowly and by 1939 was down to 10,000, living up to the capacity of the range, now seriously damaged by overcropping. With the range still deteriorating, starvation continued to kill more deer than the predators had" (Simpson, et al., 1957, p. 655). It was enough to point out that scientists, foresters, park rangers, game wardens, hunters, and wildlife enthusiasts alike had learned the important lesson.
  Scientific studies of the deer population continued, however, as did the calls for ever-more scientific expertise. The divided jurisdiction of the preserve remained problematic. In 1970, ecologist Graeme Caughley reviewed the tangled evidence of the lesson and questioned the way two generations of textbook authors had perpetuated Leopold's use of the Kaibab example. The evidence, Caughley suggested, was found wanting and the textbooks were just plain wrong in stating that predator control alone had caused the Kaibab irruption. He concluded that predators had a relatively minor influence on the deer population. More significant were variations in habitat caused by factors including climate, livestock grazing, and changing federal and state wildlife policies (Caughley, 1970).

After Caughley's critique, textbooks purged references to the Kaibab deer altogether. Authors and teachers began to describe irruptions without reference to any specific case. In one textbook, the case is used to point out the difficulties of using historical cases in science textbooks, because they contain more than theoretical or conceptual complexity (Baker and Allen, 1977).

Ecologists and wildlife biologists continue to debate the dynamics of predator and prey populations in actual practice (McCullough, 1997).


Baker, J.J.W. & Allen, G.E. (1977). The Study of Life: Biology 3rd ed. Philippines: Addison-Wesley.

Caughley, G.
(1970). Eruption of ungulate populations, with emphasis on Himalayan Thar in New Zealand. Ecology 51(1), 53-72.

Foster, J.C. (1970). The deer of Kaibab: Federal-state conflict in Arizona. Arizona and the West 12, 255-268.

Leopold, A.S. (1949). A Sand County Almanac: With Essays on Conservation from Round River. Oxford: Oxford University.

Mann, W.G. (1941). The Kaibab Deer: A Brief History and the Present Plan of Management. Williams, Arizona: Kaibab National Forest.

McCullough, D. (1997). Irruptive behavior in ungulates. In W.J. McShea, H.B. Underwood & J. H. Rappole (Eds.), The Science of Overabundance: Deer Ecology and Population Management (pp. 69-98). Washington, DC: Smithsonian Institution.

Rasmussen, D.I.
(1941). Biotic communities of the Kaibab Plateau, Arizona. Ecological Monographs 11(3), 229-75.

Roosevelt, T. (1913). A cougar hunt on the rim of the Grand Canyon. Outlook 105, 259-266.

Simpson, G.G., Pittendrigh, C.S. & Tiffany, L.H. (1957). Life: An Introduction to Biology. New York: Harcourt, Brace, and Company.

Young, C.C. (1998). Defining the range: Carrying capacity in the history of wildlife biology and ecology. Journal of the History of Biology. 31(1), 61-83.

Last updated: October 10, 2001; Created: 20 April 2001.