Kaibab Plateau deer disaster
The Kaibab Plateau deer disaster refers to a significant fluctuation in the mule deer population on the Kaibab Plateau in Arizona, occurring from 1906 to 1939. Initially, the population surged from approximately 4,000 deer in 1906 to an estimated 100,000 by 1924, largely attributed to extensive predator control and a reduction in livestock grazing following the establishment of the Grand Canyon National Game Preserve by President Theodore Roosevelt. However, this dramatic increase led to overgrazing and food depletion, exacerbated by two severe winters in the mid-1920s, resulting in a reported population decline of about 60 percent, leaving fewer than 10,000 deer by 1939.
Researchers have since debated the accuracy of population estimates from this period, highlighting inconsistencies and a lack of rigorous scientific methods in the data collection. Notably, the work of researcher Graeme Caughley questioned the reliability of the reported figures, suggesting that the deer population may have stabilized around 30,000 rather than experiencing the drastic decline once thought. The events on the Kaibab Plateau serve as an important case study on the complexities of wildlife management and the impacts of human intervention on natural ecosystems, illustrating how changes in predator and prey dynamics can lead to unforeseen consequences.
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Kaibab Plateau deer disaster
THE EVENT: Eruption and crash of the population of mule deer on the Kaibab Plateau in Arizona
DATES: 1906-1939
The Kaibab Plateau deer disaster is frequently cited as an illustration of the adverse impacts humans can have, particularly through predator control, on the natural balance between animal populations and their environments.
The Kaibab Plateau, part of the Kaibab National Forest, lies on the North Rim of the Grand Canyon in Arizona. In 1906 President Theodore Roosevelt set aside the Grand Canyon National Game Preserve, including the Kaibab Plateau, for the protection of game animals. As part of this protection, government trappers removed thousands of predators from the region between 1906 and 1931, including mountain lions, coyotes, bobcats, and the last remaining gray wolves. Livestock grazing by sheep, cattle, and horses was also greatly reduced between 1889 and 1931.
Following this reduction of predators and competing livestock, the mule deer (Odocoileus hemionus) of the plateau was described as having increased from 4,000 in 1906 to 100,000 in 1924. After depleting its food supply and experiencing two consecutive harsh winters (1924-1925 and 1925-1926), approximately 60 percent of the herd purportedly died, and the population reportedly declined to fewer than 10,000 in 1939.
Researcher Graeme Caughley later evaluated the available information and challenged both the descriptions of the events that took place and their interpretation. Caughley noted that most of the population estimates were based on poor data. For example, estimates of the peak population in 1924 by different biologists and visitors to the area varied from 30,000 to 100,000 deer, and none of these estimates was grounded in sound scientific studies. The purported 60 percent decline (from 100,000 to 40,000 deer) was actually an extrapolation from one visitor’s estimate of a 60 percent decline from 50,000 to 20,000 deer between 1924 and 1926. The only deer population estimates with any continuity over this period were made by the forest supervisor, who reported a general increase from 4,000 deer in 1906 to approximately 30,000 deer in 1923; notably, he also reported a stable population of approximately 30,000 deer over the time span (1924 to 1929) of the purported population crash. Thus many of the figures available on the Kaibab deer herd between 1906 and 1939 have been judged to be unreliable and inconsistent.
Overall, there is reasonable field evidence for a significant population increase, some starvation, and a population decline among the deer of the Kaibab Plateau between 1906 and 1932. In a general fashion, the increase in deer numbers coincided with a predator-control program and a reduction of livestock grazing in the region. Caughley argued that the Kaibab deer eruption, like similar eruptions observed in other ungulates (hoofed animals), was most likely linked to changes in food or and was terminated by depletion of food supplies. In summary, however, the magnitude, timing, and causes of the Kaibab deer population eruption and crash are unclear. Few scientific conclusions about human impacts on ungulate populations can confidently be inferred from these events.
Bibliography
"Ecosystem Collapse--Kaibab Plateau." Oasis 10, 16 Sept. 2023, https://oasis-io.com/blog-model-kaibab-plateau-collapse-effects/. Accessed 19 July 2024.
Rue, Leonard Lee, III. “A Historical View of Management Problems.” In The Deer of North America. 1997. Reprint. Guilford, Conn.: Lyons Press, 2004.
Young, Christian C. In the Absence of Predators: Conservation and Controversy on the Kaibab Plateau. Lincoln: University of Nebraska Press, 2002.