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The Lesson of the Kaibab.pdf
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The Lesson of the Kaibab
Introduction: The environment may be altered by forces within the
biotic community, as well as by relationships between organisms
and the physical environment. The carrying capacity of an
ecosystem is the maximum number of organisms that an area can
support on a sustained basis. The density of a population may
produce such profound changes in the environment that the
environment becomes unsuitable for the survival of that species. For
instance, overgrazing of land may make the land unable to support the grazing of
animals that lived there.
Graph data on the Kaibab deer population of Arizona from 1905 to 1939
Determine factors responsible for the changing populations
Determine the carrying capacity of the Kaibab Plateau
Before 1905, the deer on the Kaibab Plateau were estimated to number about 4000. The
average carrying capacity of the range was then estimated to be about 30,000 deer. On
November 28th, 1906, President Theodore Roosevelt created the Grand Canyon National
Game Preserve to protect the “finest deer herd in America.”
Unfortunately, by this time the Kaibab forest area had already been overgrazed by
sheep, cattle, and horses. Most of the tall grasses had been eliminated. The first step to
protect the deer was to ban all hunting. In addition, in 1907, The Forest Service tried to
exterminate the predators of the deer. Between 1907 and 1939, 816 mountain lions, 20
wolves, 7388 coyotes and more than 500 bobcats were killed.
Signs that the deer population was out of control began to appear as early as 1920 – the
range was beginning to deteriorate rapidly. The Forest Service reduced the number of
livestock grazing permits. By 1923, the deer were reported to be on the verge of
starvation and the range conditions were described as “deplorable.”
The Kaibab Deer Investigating Committee recommended that all livestock not owned by
local residents be removed immediately from the range and that the number of deer be
cut in half as quickly as possible. Hunting was reopened, and during the fall of 1924,
675 deer were killed by hunters. However, these deer represented only one-tenth the
number of deer that had been born that spring. Over the next two winters, it is
estimated that 60,000 deer starved to death.
Today, the Arizona Game Commission carefully manages the Kaibab area with
regulations geared to specific local needs. Hunting permits are issued to keep the deer in
balance with their range. Predators are protected to help keep herds in balance with
food supplies. Tragic winter losses can be checked by keeping the number of deer near
the carrying capacity of the range.
1. During 1906 and 1907, what two methods did the Forest Service
use to protect the Kaibab deer?
2. Were these methods successful?
3. Why do you suppose the population of deer declined in 1925,
although the elimination of predators occurred?
4. Why do you think the deer population size in 1900 was 4,000
when it is estimated that the plateau has a carrying capacity of
5. Based on these lessons, suggest what YOU would have done in the following years to
manage deer herds.
6. It is a criticism of many population ecologists that the pattern of population increase and
subsequent crash of the deer population would have occurred even if the bounty had not
been placed on the predators. Do you agree or disagree with this statement. Explain your
7. What future management plans would you suggest for the Kaibab deer herd?
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