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) men