In 1935, C.W. Quaintance took special notice of porcupines because of
the possibility, then being considered, of their being detrimental to
habitat conditions thought to be favorable to wild turkeys. Porcupines
were suspected of killing ponderosa pine, which occurred in only a few
places, and which was thought to be necessary for wild turkeys.
Porcupines were recorded as follows: one found dead on the road at the
North Rim on March 16; one killed in oak brush along the North Rim; one
killed between April 15 and May 15; oak brush damaged by porcupines in
Soda Canyon below the well; one seen on July 4 on the Poole Canyon
Trail; one seen at the foot of the Mesa on June 26; one seen by Lloyd
White in Moccasin Canyon on June 27; and one seen by Mrs. Sharon Spencer
on July 1 in Prater Canyon. After four months on the Mesa Verde,
Quaintance concluded that there were not so many porcupines as had been
expected and that there were more ponderosa pines than had been
expected.
In 1946, Donald A. Spencer began a study of porcupines on the Mesa Verde
and in 1958 deposited, in the University of Colorado Library, his
results in manuscript form as a dissertation in partial fulfillment of
the requirements for a higher degree ("Porcupine population fluctuations
in past centuries revealed by dendrochronology," 108 numbered and 13
unnumbered pages, 39 figures, and 13 tables). Dendrochronology, or the
dating of trees by studying their rings, is a technique widely used in
the southwest by archeologists, climatologists, and others. Spencer
found that porcupines damage trees in a characteristic manner, and that
damage to a pinyon pine was evident as long as the tree lived. By dating
approximately 2000 scars and plotting the year for each scar, Spencer
observed three peaks since 1865; these were in about 1885, 1905, and
1935. The increase and decrease each time were at about the same rate.
The study did not yield precise population estimates. Some porcupines
were destroyed but Spencer is of the opinion that the decline that came
in following years was independent of the control measures. Spencer
thinks that activities of porcupines on the Mesa Verde are a major
factor in maintaining a forest cover of relatively young trees, and also
in preventing invasion of trees into areas of brush.
The general policy in regard to porcupines from 1930 to 1946 was to kill
them because they eat parts of trees. In at least the following years
porcupines were killed: 1930, 1933, 1935, 1940, 1943, 1944, and 1946.
The largest number reported killed in one year is 71 in 1933 when a crew
of men was employed for this purpose. The amount of effort devoted to
killing porcupines varied from year to year. The most frequently voiced
alarm was that the scenic value of the areas along the entrance highway
and near certain ruins was being impaired. The direst prediction was
that all pine trees on the Mesa Verde were doomed to extinction in the
near future. The last prediction has not come to pass, nor has this
extinction occurred in the past thousand years and more during which
pine trees and porcupines have existed together on the Mesa Verde.
In 1946 the studies of Spencer, Wade, and Fitch began. Much effort was
expended in obtaining and dating scars for analysis, and the interesting
results mentioned above were the reward. Also many porcupines were
captured alive and marked with ear-tags so that they could be recognized
later. For example, in the winter of 1946 and 1947, 117 were marked in
Soda Canyon. A decline in numbers in recent years reduced the impetus
for continuation of the study by reducing the results obtained for each
day spent searching for porcupines. Information obtained on movements of
porcupines relative to season and weather conditions in these studies
may be summarized and published later. Data regarding ratio of young to
adult animals from year to year are also of interest.
The effect of a porcupine on a single tree is often easy to assess. The
effect of a fluctuating population of porcupines on a mixed forest is
not so easy to assess, but is of more intrinsic interest. It is
desirable that studies designed to evaluate the latter effect continue
while the population remains low and also when the next cyclic increase
begins. Publication of Spencer's results would be a major step forward.
Cahalane (1948:253) mentions the difficulty that has been experienced in
protecting aesthetically desirable trees around cliff dwellings. Perhaps
in a local area removal of porcupines is sometimes warranted, but
control of the porcupine seems undesirable to me, as a general policy,
because one purpose of a National Park is to preserve natural conditions
and that implies naturally occurring changes.
What is needed is continued careful study of the ecological
relationships of animals and of plants. National parks provide, to the
extent that they are not disturbed or "controlled," especially favorable
places for studies of this sort.