SIERRA CHICKAREE. Sciurus douglasii albolimbatus Allen

Field characters.—Body size a third that of Gray Squirrel, about equal to that of House Rat; tail about 2/3 length of head and body, brush-like, with long hairs at sides; ears tall, slightly tufted (fig. 29). Head and body 7-3/8 to 8-1/4 inches (188-209 mm.), tail 4-3/8 to 5-1/2 inches (111-139 mm.), hind foot about 2 inches (48-54 mm.), ear (from crown) 4/5 to 1-1/5 inches (21-30 mm.); weight 7-3/4 to 10-1/2 ounces (218-299 grams). General coloration above dark brown; a reddish tinge along back; a black line along each side sharply marking off the white or buffy color of under surface; feet light reddish brown; tail blackish with silvery white hair-tippings. Voice: A short explosive note, quer-o, often repeated; also a prolonged whickering or whinneying, of high-pitched notes uttered 4 or 5 a second and continued for several seconds. Workings: Pine and fir cones cut green and cached on ground about logs; kitchen middens consisting of remains of comes which have been dissected, on the ground (fig. 31), on tops of logs (pl. 36b), or on large rocks; freshly cut foliage scattered on ground beneath trees (pl. 35b).

Occurrence.—Common resident throughout Canadian and Hudsonian zones to extreme upper limit of forest on both slopes of Sierra Nevada; sparingly represented in upper part of Transition Zone on west slope. Recorded from Sequoia, Hazel Green, and Chinquapin eastward across mountains to Leevining Creek and Walker Lake. Also on Mono Craters. Found at times in Yosemite Valley. Altitudinal range 4000 to 11,000 feet. Inhabits coniferous trees. Diurnal. Solitary.

From the lower border of the fir woods to the extreme upper limit of tree growth, the most conspicuous day-moving mammal is the Sierra Chickaree or Red Squirrel. This species is not found in the company of its relative, the Gray Squirrel, save where the ranges of the two overlap slightly on the west slope and in the exceptional instances when the chickarees in numbers move down into the Transition Zone. Near Sequoia, at Hazel Green, and at Chinquapin the two have been found together. Occasional individuals are to be seen in Yosemite Valley; in the winter of 1918 large numbers of Red Squirrels moved down into the Valley from the surrounding high country, and some of them were still present at the beginning of summer in 1919. Individuals were seen in May of that year near Stoneman Bridge and opposite the base of Rocky Point. Locally the chickaree is known as pine squirrel, Douglas squirrel, and "bummer" squirrel.

The Sierra Chickaree is characteristically arboreal, and comes to the ground less often even than the California Gray Squirrel. Ordinarily it comes down only when attending to the disposition of cones which it has cut down, when going to drink, and when crossing open spaces between widely separated trees. Whenever possible it travels aloft, through the trees, jumping from one to another across gaps between their adjacent branches. The following account of the behavior of one of these squirrels at Glen Aulin, October 4, 1915, will indicate something of the strong desire of the animal to keep aboveground in the presence of danger. This squirrel, when come upon by one of our party, was on the ground. It ran quickly to the nearest lodgepole pine, ascended about 25 feet, ran out on a branch and jumped to a second tree. There it ascended about 5 feet higher and jumped to a third tree. This tree was separated from other neighboring trees by a distance too great for the animal to negotiate in a jump from branch to branch. The squirrel recognized this fact very quickly after running out on a limb, for almost immediately it returned to the trunk, descended rapidly to the ground, and ran to a fourth tree. This tree, too, was isolated from its neighbors, and the squirrel after climbing a few feet dropped down and ran to a fifth tree from which it was able to make off through the dense forest without having again to come to the ground. These squirrels will climb to the uppermost branches of forest trees, well out of shotgun range. In jumping, the animals can cover 3 or 4 feet at a single leap.

The Sierra Chickaree is remarkably endowed with 'vocabulary,' and in this respect is far better off than any of the other local squirrels. If the curiosity of a chickaree is piqued by a person's 'squeaking,' or from other cause, the animal will often come within a few feet of the observer and while clinging to the side of a tree by means of its sharp claws will utter a sharp interrogative-sounding note, quer-o or quir-o, every few seconds, accompanying each utterance by a spasmodic jump and a quick jerk of the tail. Not infrequently, if a person sits down under the tree in which one of these squirrels is performing, the animal will keep up this behavior for many minutes, occasionally retiring and then coming back for another look at the intruder and another series of vocal expressions. If the observer happens to jump up suddenly, the startled squirrel usually makes off up the tree, uttering a series of high-pitched squealing notes and 'galloping' so vigorously and rapidly up the trunk that a shower of bark slivers is dislodged as it goes. When undisturbed, off in the depths of the forest, the chickaree from time to time utters a prolonged series of whickering or whinneying notes of somewhat the same character as the single note, but in rapid succession, 4 or 5 a second, and this is kept up for several seconds. Such a series is sometimes answered by other squirrels in the neighborhood. When come upon suddenly a squirrel may give a single, startled, high-pitched squeal as it bounds toward safety. The young, during the fall months, can often be distinguished from the adults by their softer, less penetrating voices.

Fig. 29. Sierra Chickaree or "Red Squirrel." Photographed from fresh specimen taken near Yosemite Point, June 4, 1915; slightly over 1/3 natural size.

The chickaree, like the Gray Squirrel, is admirably adapted for life in the trees. The body is lithe yet muscular; the claws on all of the feet are curved and sharp so as to catch readily on the bark. (See fig. 29.) In going up a tree, the animal gallops, using the fore and hind feet in pairs; but in descending, it goes head downward moving the feet individually. On the ground the gait is also a gallop with the hind feet spread widely apart, carried forward at each bound, and planted ahead of the forefeet.

Despite the agility of the chickaree, occasionally an individual loses its foothold in a tree and falls to the ground. A young badly frightened animal at Gentrys in October, 1915, lost its footing and fell a distance of about 20 feet. Yet it immediately picked itself up and scampered up another tree. A tree squirrel seems able to distribute the shock of impact with the ground by spreading out all of its feet widely, thus saving itself from serious injury.

Tree squirrels, generally, are abroad all the winter. They are able to find food in greater or less abundance, even when the ground is covered with snow. Furthermore, the chickaree goes to great pains to provide a winter store of food, to be used to supplement whatever the animal can find by random foraging. In the late summer and early autumn, when the cones of many of the evergreen trees have attained full or nearly full size but are still green, the chickarees begin their annual harvest. The busy animals gnaw off the cones, and as a person walks through the forest where the squirrels are operating, cones may be seen or heard falling at frequent intervals. In fact there is some danger in being under the trees, especially when the heavy green cones of the Jeffrey pine, weighing several pounds apiece, come down from a height of a hundred feet or so. The cutting is more or less indiscriminate, as cones in all stages of development are cut—those in which seeds are well advanced as well as others in which the seeds are but partly formed. (See figs. 30, 31.)

Fig. 30. Sugar pine cones, (a) as cut down green by the Sierra Chickaree, (b) as matured and dropped naturally by the tree, and (c) the green cone core left after a squirrel has cut off the scales and eaten the seeds.

After cutting for a while a squirrel will descend to the ground and proceed to dispose of the cones which it has detached. Such cones as are not wanted for immediate use are cached on the ground under the sides of downed tree trunks and in other nooks and crannies in the vicinity of the animal's home. Cones so sheltered do not dry out so rapidly as they would if left out in the open. This is particularly important in the case of the cones of the white and red firs, as these, upon drying, go to pieces quickly and the seeds are scattered. In winter, when snow is on the ground, or in early spring, when other forage material is scarce, these cones which have been in cold storage are dug out and the seeds eaten.

An idea of the amount of work done by the chickarees in the Yosemite region may be gained from the following counts and estimates. At Aspen Valley, in October, 1915, a chickaree was found to have its headquarters close to our camp. The animal inhabited a group of seven white firs beneath which was a prostrate trunk. Within an area 50 by 50 feet in extent the junior author gathered 484 cones which had been cut down, evidently by this one squirrel (pl. 35a). Most of these had been carried to the side of the log where some had been partially buried in the ground. Others had been put into crevices in nearby trees. In one case a hole in a log about 18 inches deep had been crammed full of the green cones. Above Yosemite Point, that same month, the senior author found the headquarters of another chickaree which had been similarly engaged. This animal had cut down about 180 cones and these were cached at the two sides of a log within an area about 20 by 60 feet. If we assume that there is 1 chickaree to every 4 acres of territory in the Canadian Zone of our Yosemite section, then the 250 or more square miles of this zone harbor approximately 40,000 squirrels. If each squirrel on the average cuts but 250 cones a season, the annual harvest of fir cones in the Canadian Zone on the west slope of the Yosemite region would be about 10 million. In addition there are many Red Squirrels in the Hudsonian Zone, and some in the Canadian Zone of the Mono region, all cutting down cones of the various species of coniferous trees present in those areas.

Fig. 31. Kitchen middens of Sierra Chickaree: shelled-out green cones of Jeffrey pine; Merced Lake, August 28, 1915.

One morning in mid-October at Aspen Valley, the same squirrel that had garnered the great number of white fir cones referred to above was seen to run down the home tree, grasp a cone in its mouth, and ascend the trunk to a short horizontal stub about 30 feet above the ground. Here it sat up on its haunches, grasped the two ends of the cone by its forefeet, and proceeded to rapidly strip off the scales. After a few scales had been removed there would ensue a few moments of rapid chewing of the exposed seeds and then more scales would be cut off and come fluttering to the ground. Most frequently the squirrel begins at the stem end and, gradually rotating the cone, strips the scales off in the order in which they are attached to the core, from base to tip. But sometimes work is begun at the tip of the cone and occasionally in the middle.

Among the great number of cones lying on the ground there are many which have been only partially dissected, and this is true also of the cones comprising the caches. These may have been sampled and then put away for future use, or perhaps an animal has been frightened and forced to drop the cone before finishing it.

At Porcupine Flat on July 1, 1915, a typical kitchen midden of a chickaree was found by the authors on top of a prostrate tree trunk (pl. 36b). The material comprised remains of red fir cones, namely cone-cores, scales, and seed wings. Several other logs in the vicinity were littered with similar debris, with accumulations on the ground beside them. Evidently there had been a fruiting fir tree near by from which the squirrel had gathered a large stock of cones the previous autumn. From time to time during the winter, as needed, the squirrel had retrieved the cones from their places of concealment, and had repaired to these logs to shell out the seeds. In early spring such logs, projecting above the snow, would also afford good lookouts whence a squirrel while at work could watch for possible danger for the approach of a red fox, a pine marten, or a hawk.

Practically all the cone-bearing trees within the range of the chickaree are levied upon for food. We saw work upon the cones of the red and white firs, the alpine hemlock, and the lodgepole, Jeffrey, and mountain pines. The white-bark pine fruits only at long intervals, so it does not play any very important part in supplying food for the chickaree.

As might be expected, the faces of the squirrels, especially during the autumn, get somewhat smeared with pitch, and from time to time individuals may be seen engaged in vigorously cleaning their faces with their forepaws. But on the whole, the animals keep remarkably clean. If a person tries to get at the seeds in a green cone he will soon come to have respect for the skill of the squirrels in handling such material without becoming hopelessly pitchy.

It might be expected that such wholesale consumption of fir seeds by the chickaree would be detrimental to the forest. But in those protected areas of the Yosemite region where man has interfered slightly or not at all with the natural balance and where tree squirrels have lived for untold generations, the forest appears to be of maximum density and the young growth coming along is sufficient to effect full replacement of natural loss among the mature trees. Despite the heavy inroads which the squirrels make, a certain percentage of cones always escapes their attention, and remains on the trees; these cones mature and scatter their seed in usual fashion. Indeed the cutting off of a considerable percentage of the fruits (cones with seeds) by the squirrels may even be of benefit to the trees. It is analogous to the operations of an orchardist who thins out the fruit on his trees in order to obtain a moderate number of full-sized, vigorous fruits rather than many small or average ones. Examination of the ground beneath pine trees patronized by chickarees shows, during the spring and summer, considerable numbers of cones in which the seed has matured naturally and has fallen before the cones themselves have dropped. It would appear that the squirrels merely harvest a surplus. At Aspen Valley, in the autumn of 1915, where tree squirrels were present in as goodly numbers as in any place which we have studied, there were in addition to mature trees many close stands of healthy young firs and pines.

Like the California Gray Squirrel the present species is thought at times to raid birds' nests, though the extent to which this is practiced is not known with any degree of accuracy. At Merced Lake on August 23, 1915, a Wood Pewee was seen vigorously pursuing a chickaree. The pewee was scolding furiously and the squirrel was retreating rapidly. At Chinquapin, on May 20, 1919, a robin was seen flying at a chickaree, snapping her beak within a short distance of the latter. The squirrel was in full retreat down a tree. Instances of this sort have been taken to mean that the squirrels prey upon eggs or young; but much direct observation is needed to prove the actual extent of the squirrel's operations in this regard.

We have, on one occasion, seen a chickaree eating the small pollen-bearing (staminate) cones of a yellow pine. This was on May 18, 1919, in the neighborhood of Nevada Falls. In late summer the tender 'needle-buds' of coniferous trees are eaten. A squirrel in Lyell Cañon on July 24, 1915, had its stomach filled with chewed-up buds of the lodgepole pine.

Red Squirrels are often attracted by meat bait placed about steel traps for the larger animals, and a considerable number of these squirrels was obtained in our efforts to trap coyotes, badgers, martens, and similar carnivores. At Merced Lake a chickaree was taken in a trip baited with fish entrails and set for mink. We also captured chickarees in unbaited traps set in burrows of Aplodontia and out of sight from aboveground. Some, at least, of the squirrels taken under the latter circumstances were probably en route to drinking places.

The autumn of 1915 witnessed great activity on the part of the chickarees in the Yosemite region. The animals were very busy harvesting their food for winter use. Old-timers in the mountains remarked to us upon this activity by the squirrels, saying that it was sign of a heavy winter coming. There was a big crop of cones that fall; and the winter of 1915-1916 did prove to be marked by heavy snowfall. But that there is any ability on the part of the native animals to predict the nature of the whole season is exceedingly doubtful.

A nest of the Sierra Chickaree was found at Merced Lake on August 27, 1915, the identity being established by seeing the squirrel itself visit the place. The nest was located in an old, much rotted and burned out Jeffrey pine stub about 15 feet high and between 5 and 6 feet in diameter. The entrance to the nest was about 12 feet above the ground, on the north side of the stub, and measured about 2 inches in vertical diameter and 2-1/2 inches transversely. This entrance hole led into an old woodpecker excavation some 6 inches in diameter and 12 or 13 inches high. In the bottom of this cavity was about a pint of fine dry material, small chips remaining from the woodpecker tenancy, and twigs, dry grass, cone scales, and squirrel faeces. From this old cavity a passageway or hollow place in the wood (of which there were many) led down into a larger cavity 18 inches in transverse diameter and nearly 36 inches in the vertical dimension. The chickaree's nest was in this place and to judge from the condition of some of the material the location had been occupied for several seasons or at least for more than one. The total bulk of material which had been carried in by the squirrel was estimated at about 12 quarts. Included were the following items: leaves and twigs of the aspen which had evidently been brought in fresh during the current and previous season; shredded bark of the aspen; moss, both green and dry; staminate cones of lodgepole pine; cores and scales of dissected pistillate cones of both lodgepole pine and Jeffrey pine; mistletoe from coniferous trees; and on top of the whole, as 'bedding,' many freshly cut twig ends of lodgepole pine, with green needles still adhering. These latter varied in length from 1-1/2 to 6 inches, averaging about 3 inches. Droppings were found in but one place in the main nest.

The outer surface of this Jeffrey pine stub was quite smooth; yet it offered no particular difficulties to the squirrel, which was seen to run down from the top past the hole, then turn around and enter the cavity. Adjacent to the stub was a thicket of aspens and lodgepole pines. The nearest live Jeffrey pine was about 50 feet away.

On June 29, 1915, we found a place on the Tioga Road a short distance east of Porcupine Flat where a chickaree had been getting material for a nest. From a slender lodgepole pine about 90 feet high and 12 inches in diameter the squirrel had cut off numerous terminal branchlets with their adhering needles, and left them strewn about on the ground beneath the tree (pl. 35b). In an area about 15 feet square we counted more than 350 twigs, and it was estimated that there were more than 500 altogether. The pieces varied from 2 to 12 inches in length, averaging about 6 inches. None of the twigs, save one or two from which apparently the young cones had been removed, showed any indication that they had been worked upon after being cut off. Comparison with other trees in the vicinity showed that one-half or more of the terminal foliage of this particular tree had been removed.

Other cuttings of similar sort were seen in the head of Lyell Cañon in mid-July. On July 24, 1915, in the same locality, a chickaree was shot while running over a rock slide. The animal was found to have a bundle of bark in its mouth. This was probably intended for nest lining.

Most of the young chickarees in the Yosemite region are born in June and July, though our data leading to this statement are rather meager. An adult female taken July 19, 1915, in Lyell Cañon contained 5 embryos. This is probably an average litter. A female taken as late as October 3 (1915) was found to have the mammary glands functional; hence, to be the mother of a late litter. The young are cared for by the parent until late September or early October, when they are half or two-thirds grown; at this time the visible chickaree population is considerably augmented by the appearance of the young, whose softer voices are then to be heard on every hand.