Fauna of the National Parks
of the United States
PROBLEMS OF COMPETITIVE ORIGIN
In general, the normal utilization of vegetation by the herbivores is no concern in administration. There are exceptions, however. These occur in two cases.
The more planting that is done in a park the more faunal complications there will be. This is an additional argument for keeping artificial landscape planting in national parks to the minimum. Some landscaping is essential in order to reestablish the native cover destroyed in the construction of buildings and roads. This applies not only to new projects but also to eradication of scars where an old road or building area is abandoned. Transplanted vegetation is in a precarious condition until it becomes established in the new location. Because it is more succulent than the older forage, and perhaps for other reasons as yet not understood, it is apt to be demolished by deer, elk, rabbits, squirrels, porcupines, and other herbivores.
The proper approach to problems of this type is to anticipate the damage in any locality by choosing the less palatable species, using sufficient seed or stock to allow for an estimated loss, or planning whatever else can be done toward meeting the difficulty from the botanical angle. It is to be hoped that the future will develop a useful management practice of this type.
The second way to meet these problems is by seeking some method of protecting the vegetation from attack. Temporary screening or fencing is expensive and incongruous on wild landscape, but it may be permitted in exceptional instances, say for a period long enough to establish shrubbery or trees in administrative centers. If rapid-growing species are used, the plants will soon be above browsing height or sturdy enough to stand full exposure.
Considerable experimental work has been carried on to discover repellents. Napthalene bags hung among the branches are said to be successful in deterring deer, but this is still in the experimental stage. Fish oils and other sprays have been tried, but these wash off quite readily.
The third possibility, and absolutely the last to be considered, is destruction of the individual offending animals. In a park, the larger vertebrates are usually prized above all other forms of wild life. Hence to kill an animal to save a plant is likely to be a cure more awful than the disease. If a careful consideration of all factors reveals that it actually will be a benefit to the whole of the park to remove the destructive animals, the usual precautions should be exercised in taking only the individual offenders and not risking the status of the species.
The discussion thus far has been limited to instances where the fauna was normal and the flora abnormal. But the problem may also be due to an abnormal faunal condition. Such is the case where the ungulates are unnaturally abundant, and this takes place frequently in the very population centers where landscaping is most necessary. The floor of Yosemite Valley is an excellent illustration of this. In such instances, the remedy of the situation lies first in restoration of the normal range-fauna relationship a question treated elsewhere in this section.
Porcupine in Mesa Verde. This is chosen for a specific example of animal injury to landscape because it involves both classes of such damage; namely, to natural growth of woody plants having an unusual value to man, and to plants transplanted for landscape improvement.
In the past few years porcupines have increased until their population is far above normal for the mesa. Such infestations of this species occur from time to time in various parts of its range from causes which as yet are unknown. Most unfortunately for man in the park, porcupines have congregated in the moist draws, destroying piñon pines that are of particular value to the essential interests of Mesa Verde as a national park.
One instance is in Cliff Canyon, directly below Cliff Palace, which is the major one of the ruins. By 1930, porcupines had barked the trees in this fine stand of piñon to the extent that many of the trees had died. There were 240 piñons in the area, over 150 of which had been damaged. It was estimated that one-third of the stand was already doomed, and the abundance of fresh gnawings pointed to the practical destruction of the entire grove in the near future.
The picturesque and natural setting of the Cliff Palace was definitely impaired. Furthermore, any destruction of the natural cover on the steep canyon slope immediately underneath endangers the preservation of the ruin by increasing the erosion. The cliff dwellings are the one and only reason for the establishment of Mesa Verde National Park and are to be protected above everything else on the mesa. At this location, the decision to remove a number of the porcupines was determined by the archeological values at stake.
The porcupine have created a second problem in Upper Soda Canyon near scenic Park Point on the entrance road. Piñons are very scarce at this end of the mesa, so that certain individual trees have a great landscape value. Considerable effort has been expended to save those taken from the right of way on the new road by transplanting them to heal the old road scars. In the draws along the road at this point, the concentration of porcupines was rapidly eliminating both old and young trees, so that with the passing of the ancient and picturesque weather-scarred veterans there would be no second crop to replace them. Rather than lose trees which it cost a great deal to transplant and others which were preserved with great care when the road was constructed, it seemed preferable to remove the marauding porcupines.
Control work in both instances was accomplished by shooting the porcupines just at those points. In this way no other species was involved and an exact check could be kept on the number of animals taken. Not the slightest chance was taken that the porcupine would be eliminated from tIme fauna of the park as a whole. Further, the species dealt with was not one in any danger of becoming extinct.