By Charles M. Bogert, Ranger Naturalist
BECAUSE of the nocturnal propensities of the porcupine, few people become acquainted with this, the second largest of the present-day rodents in North America. Nevertheless, in the forests of both the Kaibab and Coconino plateaus porcupines are quite abundant. On several occasions during the months of July and August as many as twenty porcupines were observed along the road between the El Tovar and Grand View Point when this twelve-mile stretch of road was driven at night.
Live specimens were collected on several occasions for use in lectures and certain observations were made upon them which it seems worthwhile to publish. During the early part of August porcupines were frequently seen in pairs. In fact, on some nights practically all adults were seen in pairs. Thus, with mating season in the first days of August, young must be born some time in the fall. So far as the writer knows, no one has yet worked out the life history of the porcupine of the Grand Canyon region, so this is only conjecture; whether a nest is made on the ground or even possibly in a tree, how the young are cared for during the winter, remain to be observed. From observations which it has been possible to make, it seems that porcupines in this region normally spend the day in tree tops, selecting a position where foliage obscures them from the ground. This habit makes the idea of a tree nest a plausible one. It should be mentioned, however, that in a few instances porcupines have been found in caves during the day.
While Grand Canyon is probably a fairly effective barrier for this species, porcupines are not confined entirely to forested Transition Zone habitats, but seem occasionally to range well down into the Upper Sonoran Zone. Evidences of their food-getting activities are prominent along both rims of Grand Canyon, and on the South Rim at least the Pinyon Pine, Pinus edulis, is most often selected. Judging by the chips left, the outer layer of dead bark is removed and only the sap-filled, growing cambium layer is eaten. While scars left by this gnawing sometimes cover extensive areas, (as much as a square foot in a single patch), never has the writer observed a tree that has been completely "ringed". Young individuals liberated after a few hours of captivity, during which they had become quite tame, would amble off into the brush, pausing to nibble the green seeds from the desert mallow. Sitting on the hind limbs with the tail as a "prop", the four-fingered hands in front would be used in bringing the stems to the mouth and with the incisors the foliage and buds would be stripped off, with intermissions for chewing and swallowing. A young captive specimen devoured canteloupe rinds (not too readily) and groaned most of the following day, exhibiting evident signs of discomfiture.
How far out of the timber porcupines range is a question, but it seems probable that a few are able to exist in the "sagebrush" areas where the timber is merging into the desert. In New Mexico near Acoma, a porcupine carcass was seen hanging from a fence post at a corn planting where Indians had doubtless found it destroying the crop. This was some distance away from any real forest, although along the edges of the valley there was a growth of juniper.
A medium-sized individual was found east of Flagstaff in a region where trees were only occasional, wedged tightly in one of the inner recesses of one of the old Indian caves in the lava near Saddle Peak.
At the present time there are two subspecies of porcupines recognized within the limits of Grand Canyon National Park - the Yellow-haired, Erethizon epixanthum epixanthum Brandt, and the Arizona Porcupine, E. e. couesi Mearns. Anthony1 states that the Arizona Porcupine is "smaller and less yellow than typical epixanthum: ears larger: quills tipped with brown; long hair tipped with whitish: brownish on muzzle, feet and underparts. Found in Arizona (Yavapai County): limits of range unknown."
Aside from the length of the ears, the only distinction made here between the two subspecies is the color. Coloration has been observed to be exceedingly variable on South Rim specimens. Young individuals were all quite similar, but adults were of every color varying in general from dark blackish-brown to yellow. Older specimens had shorter quills than the young, but were more densely covered, especially in the region behind the head. It seems plausible that the quills are not shed, but are lost only in encounters with enemies.
It is proposed to collect a series of porcupines of various ages from each rim and subject the two subspecies to a more rigid comparison to determine the validity of the classification of couesi and epixanthum.
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