Part 5

As the map shows, _Sciurus aberti_ and its many forms are confined in the United States mainly to the high country along parts of the Colorado River, and also to that great escarpment known as the Mogollon Rim, whose length is divided about equally between New Mexico and Arizona. In this range is found what is often referred to as the “greatest unbroken stand of ponderosa pine to be found in this country.” Of the many species of plants and animals found as associates of this forest, perhaps none is more dependent on ponderosa pine than the tassel-eared squirrel. This rough-barked tree furnishes a major source of food and shelter. In return, for Nature always demands that restitution be made, the squirrels plant a part of the seeds that insure continuation of the ponderosas.

It is a common belief that squirrel’s diet consists of nuts and little else. This is true only to a degree. A squirrel is fond of nuts and will eat and hoard them during the short season when they are available. For the greater part of the year, when its stores have been depleted, it turns to many other types of food among which are fruit, herbage, leaf buds, and flowers. Favorite food of the tassel-eared squirrel is, of course, the large single-winged seeds found under scales of ponderosa pine cones. Next favored are acorns from the oak that mingles with pine at the lower edge of the Transition Life Zone. If the season is good, great quantities of cones and acorns are buried for future use. These are hidden singly, not in caches, as is the habit of some squirrels. In the event the squirrel does not return for its hidden stores, some of the seeds will sprout eventually and take their part in the slow cycle of growth and decay that is continually going on in the forest.

During months when these favorite foods are scarce, squirrels find the cambium layer of young pine twigs very acceptable. This is the tender layer that lies between the wood and the bark. In the growing season it is especially sweet and nutritious. This was as well known to the Indians as the squirrels, and they too took advantage of the supply during times of famine. The squirrel obtains this food by cutting off the terminal clusters of needles, then severing a denuded portion of the branch, of a size that may be conveniently carried to a favorite eating place. Here the outer bark is deftly removed, the edible portions consumed, and the base wood cast to the ground. Although large numbers of the terminal twigs are taken, the trees seem to suffer no serious damage from this seasonal pruning.

In selecting a nesting site the tassel-eared squirrel turns again to its favorite tree, the ponderosa pine. Because few of these healthy giants have knotholes or cavities of a size to accommodate this large species, the nests are usually built in the thick upper growth of branches. Material for their construction consists of small twigs of deciduous trees, cut with the leaves on them. These are cleverly woven together so that as the leaves wither and dry they tend to hold the bulky mass together. Aspen branches frequently are used when available, the large, almost round leaves combining to form a warm wall and at the same time a thatch impervious to all but the most driving rains. Several exits are provided in case an enemy should enter the nest, and the interior is lined with soft fibers. Usually more than one nest is built by each squirrel, so that in an area where they are common the bulky homes are conspicuous not only for their size but by reason of their numbers. With several ports in a storm, so to speak, the squirrels weather the winter very well. During the coldest days they remain snugly curled up in their nests, but on bright, still days they will be seen searching out their hoarded supplies, even though they may have to dig through several inches of snow to get to them. At such time their gruff bark, deep in timbre, may be heard for a considerable distance.

Breeding takes place in early spring, often before the snow is off. The squirrels are fully polygamous, which is one of the reasons this species can almost disappear and then restores its numbers within a season or two. There may be two litters each year, the first arriving as early as May and the second in August or September. As mentioned before, this species is variable and the young may differ in coloration from their parents and from each other. Melanistic individuals are frequent; these should not be confused with the Kaibab squirrel which they resemble superficially. Several subspecific forms are recognized but are not easily identified by the layman.

One’s first introduction to this beautiful species is an experience long to be remembered. It was no less interesting to the early naturalists who first penetrated the wild regions where it lived. Their accounts abound with adjectives such as, “handsome,” “graceful,” etc. Dr. S. W. Woodhouse, who accompanied the Sitgreaves expedition on the exploration of the Zuni and Colorado Rivers, noticed it at once and formally described it as a species in 1852. Since that time it has been introduced into many of the “sky island,” mountains that lie south of its original range. It adapts very well to new conditions, seeming to need only a favorable climate and a ponderosa pine forest in which to live. What effect its presence will have on these new surroundings is not yet known. There is always danger that the native plants and animals will suffer from such new competition in an established association. Such introductions should never be made without a study of all the factors involved.

Kaibab squirrel _Sciurus kaibabensis_ (Latin: shade-tail ... from the Kaibab, a forest in northern Arizona)

Range: An area approximately 30 × 70 miles in size in northern Arizona. The southern limit is bounded by the north rim of the Grand Canyon of the Colorado, and much of the range is included within the boundaries of Grand Canyon National Park.

Habitat: Ponderosa pine forests in Canadian and upper Transition Life Zones.

Description: A tassel-eared squirrel with an _all white_ tail. In size this species is the same as _Sciurus_ _aberti_ but the coloration is different. The Kaibab squirrel has the same rich, chestnut brown area along the back and upper part of the head, but the sides are deep gray and underparts gray to black. The tail is either all silvery white or it may have barely discernible light gray edging on the upper surface. Nesting and breeding habits are the same as with _aberti_.

This beautiful squirrel has a distinctive appearance and an uncertain specific rank. It is included here because of all the mammals discussed in this booklet it best exemplifies the effects of isolationism. There is little doubt that the ancestors of both _aberti_ and _kaibabensis_ were of one common stock. How the progenitors of the Kaibab squirrel came to be marooned on the North Rim of the Grand Canyon is of little moment. Perhaps they were already there when the Colorado plateau was young and the river was just beginning its mighty task. Possibly they emigrated later when the gorge was not as deep as it is now. At any rate, it can be assumed that they have lived on the North Rim for thousands of years, isolated from their cousins on the South Rim by only 20 miles of thin air horizontally, but a trip on foot that involves a descent of a mile through two life zones (Upper Sonoran and Lower Sonoran), a crossing of a wide and turbulent river, and an ascent to the South Rim through the same two desert zones. Surely this is an undertaking for a squirrel of the cool forests that would be too hazardous to be successful, even if attempted.

The factors that have changed this squirrel’s coloration are not definitely known, but climatic conditions are probably at least partially responsible. The North Rim is approximately a thousand feet higher than the South Rim and is considerably colder. At this higher elevation much of the Kaibab squirrel’s habitat falls within the Canadian Life Zone. This in turn makes certain vegetable food available which is rare or unknown on the South Rim. Thus diet also may have something to do with its unusual appearance.

At various times the Kaibab squirrel has been known as a distinct species, _Sciurus kaibabensis_; at others, it has been considered merely a subspecies of _Sciurus aberti_. The latter is its standing at this time. Regardless of specific rank, it is a form that should be stringently protected. The population is small and goes through the same fluctuations as _Sciurus aberti_. During the summer of 1946 only one individual was known in the area around Grand Canyon Lodge, where they usually were found in some numbers. At such times the heedless destruction of only a few squirrels could conceivably result in the extermination of this rare and beautiful animal.

Arizona gray squirrel _Sciurus arizonensis_ (Latin: shade-tail ... of Arizona)

Range: Central to southeastern Arizona and adjacent parts of western New Mexico in the Upper Sonoran and Transition Life Zones.

Habitat: Associated with the native black walnuts of canyons, or often found among the pines on canyon rims.

Description: The common gray tree squirrel to be found in the range given above. The Arizona gray is a large animal. Total length is from 20 to 24 inches with a large tail accounting for from 10 to 12 inches of this measurement. In the typical form the color is dark gray above with underparts and feet pure white. The tail also is dark gray with a silvery white margin. The finest examples of this species may be found along the edge of the Mogollon Rim in Arizona and New Mexico. Farther south the pelage often has a yellowish or brownish tinge. In the mountains along the border the Arizona gray squirrel should not be confused with the Mexican fox squirrel (Apache squirrel) which here barely invades the United States. The Mexican cousin, about the same size as _Sciurus arizonensis_, is definitely yellowish brown and has lighter underparts of the same color. Like other large tree squirrels of the west, the Arizona gray builds a bulky nest of leaves and twigs, usually in the upper branches of a deciduous tree. Young, four or five to a litter; under exceptionally favorable conditions two litters may be reared in one season.

When compared with the royal tribe of Abert’s squirrels, this common gray animal of the Southwest seems but a peasant. When it is seen alone comparisons are forgotten. Deliberate in its movements, whether crossing the forest floor or traveling the leafy aisles of the tree tops, it seems always to have calculated its next maneuver. The result is a careless grace that presents the sturdy body and beautiful tail to the best advantage. Calm in temperament and with but little of the suspicious nature that is characteristic of the smaller squirrels, the Arizona gray may easily be tamed in outdoor surroundings and becomes one of the most satisfactory of wild friends. It is not recommended, however, that they be fed from the hand or handled at any time. “Familiarity breeds contempt” is a saying that does not apply to humans alone. A squirrel’s bite can be serious as well as painful.

Both Mearns and Bailey, who wrote of this species many years ago, mention it as occurring mostly among the walnut trees of the Upper Sonoran Life Zone. Perhaps during the intervening years the press of civilization has driven them from their chosen habitat into a higher elevation. At any rate, although they still frequent the more isolated valleys, they are now found also in considerable numbers among the pines of the Transition Life Zone. The rough broken country along the Mogollon Rim seems best suited to their requirements, and they are now quite abundant there.

Along the border of the Upper Sonoran and Transition Life Zones this adaptable animal finds a wide variety of food. Although the squirrels generally are known as gatherers and storers of nuts, there are many other types of vegetable food that they will take when conditions warrant. The cambium layer of bark and leaf buds of various species of trees are eaten in spring when nut stores have been depleted. Berries, fruit, and even flowers form a considerable part of the diet during the summer. In the fall the ripening crop of pine nuts and walnuts provides not only food for immediate use but stores for the long winter season when, unless enough has been laid by, the unfortunate may starve to death. The gathering period is a time of unremitting labor. From dawn to dusk the squirrels work feverishly carrying nuts to the hiding places they have selected. Sometimes these are in a hollow tree or a nest, but usually the harvest is buried in the humus and debris that collect about the bases of trees.

There are two phases to the work. In the first the squirrel works in the tree cutting off the cones or nuts and letting them fall to the ground. When a considerable number have been thrown down, it descends and carries them away, one at a time. The latter operation is the most dangerous since enemies have an undue advantage over this aerialist when it is on the ground. During the harvest the squirrels plainly show the effects of their work. In gathering pine cones the fur of their forelegs and undersides becomes matted with pitch. The juice of walnut fruits (related to the eastern black walnut, _Juglans nigra_, which the early pioneers used as a source of dye for coloring their hand-loomed cloth) stains their underparts a dirty brown. These marks of their labor remain with them until the summer coat is shed to make way for the heavy winter pelage.

When the generic name _Sciurus_ (meaning shade-tail) is mentioned, I am reminded of an Arizona gray squirrel I observed several years ago. During late fall my wife and I were camped near the headwaters of the Hassayampa River in a mixed forest of hardwoods and conifers. Our arrival had interrupted the work of a squirrel which was gathering walnuts in the immediate vicinity, but he soon became accustomed to our presence and renewed activities. Every sunny hour he was busy storing the nuts, many of them at the base of an old pine tree near camp. Shortly thereafter a fall storm set in and lasted for several days. It developed into a pattern of misty drizzle followed by periods of clearing weather when the sun might appear for a few minutes. During sunny intervals the squirrel would appear, but as soon as it became overcast again he would as quickly disappear. Finally we discovered his retreat. When it would threaten more rain he would run up the trunk of the pine to the first branch. Here he would turn his rump to the hole and hunch up into a small furry ball with his long bushy tail laid forward over his back and head and extending down in front of his nose, forming an admirable protection against the few drops that spattered down through the thick foliage overhead.

Squirrels are not the only animals who use their bushy tails for protection against the elements. Many mammals curl up and wrap the tail around themselves for warmth, but only the squirrel tribe has a tail long, wide, and flat enough to be used as a roof. Though the origin of the term _Sciurus_ has been lost, it is not too far fetched to suppose that it was suggested by a squirrel’s use of its tail as a parasol.

Spruce squirrel, Pine squirrel (DOUGLAS SQUIRREL, CHICKAREE) _Tamiasciurus hudsonicus fremonti_ (Greek: tamia, steward and Latin: sciurus, shade-tail ... of the Hudson, named after Fremont)

Range: Utah, Colorado, Arizona and New Mexico in the Hudsonian and Canadian Life Zones.

Habitat: Conifer forests, preferably spruce, in the higher mountains.

Description: A small gray squirrel, usually the only squirrel to be found at the elevation at which it lives. Total length 13 to 14 inches. Tail 5 to 6 inches. Two distinct colors of pelage are seasonal. The winter coat is olive gray to rufous gray above with lighter underparts; the summer coat is brownish gray to yellowish gray with almost white belly and feet. A black stripe along the sides is prominent at all seasons. The tail is narrow and noticeably shorter than the body. It is gray beneath, rufous gray above, with black border and a black tip. Little is known of the breeding habits. The four young are born in early summer and by August are usually out foraging with the mother.

Spruce squirrels (distribution shown in accompanying map) include several of the more than two dozen varieties of red squirrels in the United States belonging to the species _hudsonicus_. Combined with several subspecies of the Douglas squirrels, (species _douglasi_, the “chickaree” of the far western mountains), they make up the genus _Tamiasciurus_. This term, a combining form of _Tamias_ (the genus of chipmunks) and _Sciurus_ (that of squirrels) clearly indicates relationship of the red squirrels to both groups. It is equally apparent in the field where the short narrow tail, the black stripe along the side, and the nervous disposition remind one of the chipmunks, while the arboreal habits, comparatively large size, and coughing bark are distinctively squirrel-like.

The spruce squirrel is seldom, if ever, found below an elevation of 6500 feet, and then only in the shady canyons on the northern exposure of mountains. From this low it will be found up to timberline, or rather just below that point at which the trees are too stunted to offer the required protection. It prefers the dense shade of heavily forested areas, so is rare near the southern limit of its range, and increasingly common in the northern portion.

In common with the rest of its group, this bright-eyed little animal keeps well informed on everything that goes on in the territory it has chosen as its own. Any intruder is thoroughly investigated, then as thoroughly castigated, and driven out if possible. Since these squirrels seem to recognize each other’s domain, a trespasser of its own kind usually leaves at the first sign of trouble. With larger animals and humans the attack consists of psychological rather than physical warfare. From a limb at a safe distance above the ground, the doughty warrior chatters and scolds with increasing vehemence as long as a passive interest is displayed by the imagined adversary. At the first threatening movement it disappears in a flash around the opposite side of the tree. Scratching noises and falling flakes of bark, together with noises of peevish defiance, indicates that it is working its way up the trunk. Suddenly it reappears on another limb some distance above the first and the real show begins. Paroxysms of rage, stamping of feet, waving of tail, and streams of invective all are meant to show that one step closer spells trouble. A few squeaks from your pursed lips and this tremendous bluff gives up to curiosity. In a few minutes the erstwhile challenger is back on the first limb trying to make out what this strange creature is about. This amusing procedure can be carried out over and over again, and usually is, just to observe the stuttering rages of which this tiny creature is capable. With more considerate treatment they soon become quite tame, although even then a quick movement will send them helter skelter to the closest tree.

It is well that this squirrel is a quick and tireless worker. The seeds it extracts from the spruce cones are so tiny it takes an enormous number of them to provide that energy. With such a quantity to handle, it is not so careful in storing the crop as some larger squirrels. A comparatively few cones are buried in the soft loam beneath the trees; the rest are stuffed into holes beneath the spreading roots or simply piled in heaps near the base of the trunk. In a year when cones are plentiful there may be a bushel or more in one of these piles. With several such piles within easy reach of the warm nest fastened in the branches of a nearby conifer, the small harvester has prospects of an easy winter ahead. Only in the most inclement weather are these active animals confined to their nests. They keep tunnels open to their supplies, and each snowfall adds to the security of the caches. All winter long the stockpiles diminish while the snow beneath some favorite perch becomes littered with the scales and discarded centers of the cones. By spring, which comes late at this elevation, the cones are gone and the squirrel returns to its summer diet of leaf buds, seeds, berries, mushrooms, and herbs.

The spruce squirrel is the last of what might be called the true squirrels in this book and, because the group has much in common as regards food, enemies, and relations to mankind, a short summary might be in order.

As has been mentioned, the principal diet of these animals is vegetable. However, all of them, if opportunity offers, will take birds’ eggs and young birds. This is not intended in any way as a condemnation of the squirrel tribe. Their inroads on the bird population are what might be termed “natural losses.” Nature long ago established a norm in bird reproduction which takes such losses into account.

The enemies of squirrels are legion. From the air, the larger hawks and owls, and even eagles, are ever alert to swoop in on them. On the ground lynx, bobcats, foxes, and coyotes take their toll. In northern Utah and Colorado the marten is one of the most important local controls on the squirrel population. Fast and powerful, the marten is equally at home on the ground or in the trees, and it is a fortunate squirrel that can escape one. The toll taken by all of these predators is high, yet the natural fecundity of the squirrel is so great that the population sometimes gets out of hand and disease has to eliminate the surplus.

In their relationship to man the squirrels are among the most remarkable of our native mammals. It is not ordinarily the purpose of this book to point out the economic importance of our mammals, but the beneficial work carried on the squirrels is too important to pass by. One of the most valuable natural resources that America has is forests. To the arid Southwest the mantles of living green that cover the mountains are invaluable. These are sweeping statements, but they are sober facts.