BELDING GROUND SQUIRREL. Citellus beldingi (Merriam)

Field characters.—Body size about that of House Rat; tail sparsely haired at sides, and short, decidedly less than half length of head and body; ears small and round, not pointed or tufted. (See pl. 2.) Head and body 7 to 8-1/2 inches (180-215 mm.), tail 2-1/3 to 3 inches (60-74 mm.), hind foot about 1-3/4 inches (41-45 mm.), ear from crown 1/3 to 1/2 inch (8-13 mm); weight 7-1/4 to 10-1/4 ounces (207-294 grams). General coloration light yellowish brown, paler on under surface of body; a broad area of bright reddish brown down middle of back. Voice: General warning call of 5 to 8 shrill short whistles, seek, in quick succession; females with young utter a single note, e-chert', at intervals. Workings: Burrows in ground, surface openings about 2 inches in diameter.

Occurrence.—Common resident in higher and more easterly portions of Yosemite region, chiefly but not entirely in Hudsonian Zone. Recorded from near Porcupine Flat and from near Merced Lake eastward to Mono Lake Post Office and to Farrington ranch near Williams Butte. Ranges upward to 11,500 feet as on Parsons Peak, and higher yet on Conness Mountain. Inhabits chiefly grassland, occasionally rocky places, or floor of open forest. Diurnal.

The Belding Ground Squirrel is a hardy, ground-dwelling member of the squirrel family inhabiting the meadows and other grass-producing areas in the higher and more easterly portions of the Yosemite section. This species is often called 'picket-pin' because of the erect, stake-like posture which it assumes when on the lookout for danger (pl. 2). Some persons have referred to it as "spermophile" (seed eater). Both of these names have a measure of appropriateness not always to be found in vernacular names. This squirrel is named for Lyman Belding, the naturalist formerly resident in Stockton who collected the specimen from which the species was first scientifically described.

The range of the Belding Ground Squirrel begins on the west slope of the Sierras at about the lower margin of the Hudsonian Zone. The western most report of its occurrence is from the upper Yosemite Creek in a location west of Porcupine Flat and due north of the Yosemite village. The first specimens actually obtained by our party were collected about two miles east of Porcupine Flat. Merced Lake is the westernmost point of record for the southern part of the section, in the drainage of the upper Merced River. The maximum abundance of the species is to be found on the larger high mountain meadows, such as Tuolumne Meadows, in the heart of the Hudsonian Zone. (See pl. 18b). While one of us was traversing the meadows in Tioga Pass on July 13, 1915, fully 100 of these squirrels were observed; and an equal number was counted about two weeks later while we were going along the floor of Lyell Cañon. The range of the species extends upward on the Sierran crest to well above timber line, for example, on Conness Mountain, Parsons Peak, and Parker Pass. On the east slope this squirrel is found down through the Canadian Zone (Jeffrey pines) even to the Farrington ranch near Williams Butte and to near Mono Lake Post Office, close to the shore of Mono Lake.

Meadows constitute the preferred habitat of this species, and by far the greater percentage of the animals are to be found in the grassland. But this environment is not absolutely essential to their welfare; for some of them live in rather rocky places and some in areas which bear a moderate stand of trees. In the latter two situations there is usually bunch grass in the neighborhood of the places inhabited by the squirrels. The limited patches of grass about many of the small glacial lakes often support small populations of the Belding Ground Squirrel.

This species is as strictly terrestrial as any ground squirrel of which we know. We have never seen one climb a tree or even a bush. Once one was seen on the top of a boulder about 3 feet in height. The Belding Squirrel is less given to clambering over rocks than the 'copperhead' or any of the chipmunks. Yet the present species, despite its habit of remaining on the ground surface, spies out its enemies, real or supposed, at fairly long distances and communicates at once with others of its kind in a way that puts all the individuals in the neighborhood on their guard.

When the traveler approaches a meadow and is still a hundred yards or more from the nearest Belding Squirrel, his ear is assailed by the alarm call of the animal, a series of shrill piping whistles, loud enough to be heard by any living creature within a quarter-mile radius. Usually there are 5 to 8 (rarely even 12) notes in rapid sequence. Other squirrels take up and repeat this calling so that on some occasions the rocky walls enclosing a meadow resound with their notes. This warning call is responded to according to the circumstances wherein the various individuals find themselves when the call is heard. Those out in the meadows usually at once run toward their burrows; others closer by, within a few yards of their homes, rise straight up on their haunches, with forelimbs pressed against the body. When an individual squirrel has assumed this position, it, too, utters the shrill whistled call. If its curiosity remains unsatisfied, as when its view of the approaching person is imperfect, the squirrel rises still farther until it is standing bolt upright on the soles of its hind feet. The call given then is apt to be of an even more penetrating quality than at first. If the person continues to approach, the squirrel drops to all fours and runs to the entrance of its burrow where sometimes it again assumes the 'picket-pin' position; but it more often remains hunched up on all fours, with its hind feet well under its body, ready to dart down the hole at an instant's further warning. Even when in the upright position at the mouth of the burrow the rapidity with which a squirrel can drop into its retreat is surprising. Once scared into the ground it stays only a short time, then pokes its head out again, to just below the level of its eyes.

When sitting erect and observing its surroundings a squirrel can often be seen to twitch its nose as if sniffing and drawing in the air. Probably it uses the sense of smell to aid its powers of sight and hearing.

On flat open land where grass is at best very short, the usual mode of progression for this squirrel is a heavy run, with little up and down movement of the body, and with the tail down. In high grass, instead of parting the stalks and running between them, the squirrel progresses by a series of jumps; each hop carries the animal up so that it can look about for some distance and be able to spy an approaching enemy.

Once a Belding Squirrel was come upon in a rocky place; the animal ran over some rocks and jumped over a creek which was fully 2 feet wide, in its effort to escape. Another, on Mount Hoffmann, ran along the face of a pinnacle of rock, clinging to small cracks in the surface.

The Belding Ground Squirrel subsists chiefly upon grass and grass seeds, and depends less upon the larger seeds, nuts, and roots such as are eaten by the California Ground Squirrel and the chipmunks. When feeding, the animal sits in a hunched-up position, the hind legs in entire support of the body. The forefeet, when grass is being eaten, are used to draw the grass stalks or heads toward the mouth where they can be cut off. Larger items are held in the forepaws, while small pieces are nibbled off with the front (incisor) teeth and rapidly ground up by the cheek teeth (molars). In a few instances Belding Squirrels were captured in meat-baited traps set for carnivores. Certain other members of the squirrel family seek flesh bait when available, but the present species seems to be more restricted in its food preferences to vegetable material. At the mule corral on Tuolumne Meadows in 1915 the 'picket-pins' were foraging around barley sacks, gleaning scattered grain like rats. Several Belding Squirrels were caught in steel traps set in the entrances to Marmot burrows, and one was captured in a Macabee gopher trap which had been set in a gopher burrow.

Each 'picket-pin' evidently restricts itself closely to use of its own particular burrow and does not, in time of danger, dart into whatever retreat happens to be nearest at hand. On Lyell Meadows one was repeatedly seen to run from the meadowland, where there were numerous holes, to a particular burrow in the granite gravel above the trail. Near the same place, one of our party suddenly came upon one of these squirrels, posted at 'observation,' within one foot of an open burrow. The squirrel, instead of darting into this nearest hole, ran to one fully 30 feet farther away.

The burrows are usually constructed right in the meadows which furnish the animals their food; less frequently they are dug in the rocky soil at the margins of the meadows. Those squirrels which live in the bunch-grass areas at or above timber line make their burrows; of necessity, in the granite soil. A typical meadowland burrow at Snow Flat was opened and studied by the authors on June 28, 1915. This burrow was close to the bank of a small creek, which meandered through the meadow, and was near a large granite boulder. The ground was heavily matted with grass roots to a depth of 1-3/4 inches (45 mm.) and all the tunnels had been excavated below this mat. The whole tunnel system was remarkably level, unlike those of the California Ground Squirrel in the lowlands; but this may have been conditioned by the nearness of the creek and of the water table. Two short, deeper tunnels which were found may have been prospects toward a deeper system which would have been excavated later in the season. There was melting snow about the meadow and the ground was quite wet on the date of our study, especially below the level of the tunnels laid open. The presence of this extreme amount of moisture may have acted to deter the squirrel from going any deeper.

The total length of all the tunnels in this system was 53.3 feet (16.25 meters) and the average tunnel diameter 2 inches (52 mm.). The total amount of earth excavated was therefore 2010 cubic inches—8.7 gallons of earth, or nearly enough to fill two 5-gallon oil cans. Yet there were no mounds of earth at the entrances to the burrow. The soil had either been pushed into the creek or else washed away by the summer rains and melting snow water.

This burrow system contained no well constructed nest; but in one place there was some grassy material, either the remains of an old nest or, more likely, the beginning of a new one. The inhabitant of this burrow was a female which would have given birth to young, within two weeks probably.

One burrow of this species was noted at the base of a lodgepole pine. In this case there was a mound of earth at the entrance.

The young of the Belding Ground Squirrel are born about the first of July, there being, so far as all our evidence shows, but one brood per year. Yet a pair was seen in what looked like a mating pursuit as late as July 13. The number of young was ascertained definitely in only one case, that of the female containing 5 embryos, at Snow Flat, June 28. A female obtained July 2 east of Porcupine Flat had evidently just given birth to 6 young. In females taken on July 8 and 21, 1915, the mammary glands were functional. The young, when they first appear above ground, are scarcely more than one-third grown. The first young were noted in 1915 on July 25. But near Williams Butte three young only a third grown were seen on June 28 (1916). At the end of July (27-31) in 1915, in Lyell Cañon and on Tuolumne Meadows, young were out at the mouths of burrows in numbers, usually in groups of five and six. At Tenaya Lake on July 29 the young animals seen were larger than those at the higher stations. It is therefore probable that the young are born earlier at the lower altitudes than at the higher levels. The record at Williams Butte goes to substantiate this belief. Full size is not attained for some weeks; young weighing scarcely more than half as much as adults were taken at Merced Lake August 31 and in Tioga Pass September 25, 1915.

As early as July 26 small new burrows with mounds of earth at the entrances were beginning to appear on Tuolumne Meadows. These were evidently made by young which had been turned out of the parental burrows to shift for themselves.

When the young first go above ground they frisk about the entrance to the burrow under the watchful eye of the female parent. In Lyell Cañon on July 25, 1915, one of us came upon a single young animal running in and about some rock crevices adjacent to the burrow at the side of the meadow. The mother was standing guard, uttering her note, e-chert', every few seconds. The observer 'squeaked,' whereupon the parent squirrel at once rose upon her hind feet in the picket-pin position and uttered the shrill piping warning call of the species; the youngster promptly ran into the burrow. The adult remained standing on her hind feet for 48 seconds, then sank down on her haunches.

A day or two later, another family group consisting of a female and 2 half-grown young, on Tuolumne Meadows, was studied at close range for some time.¹⁴ At first the youngsters did not venture very far out of the hole; and when they did they remained on the far side of their mother. Later, they gained courage and came more into view, one being more venturesome than the other. The mother stood much of the time in the picket-pin position giving the e-chert' call. At each utterance her body was shrugged up, the head and shoulders thrown forward and the tail given an upward flip; much effort seemed to be put into the production of this note. In cases where families of 5 or 6 young were seen, they all sat close about the entrance of the burrow and when frightened all attempted to crowd into the hole at the same instant. One youngster, bewildered by some horses, ran directly at one of our party and then escaped into a shallow hole some distance from its home burrow.

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¹⁴This was done by the method of direct approach. The observer garbed in dull brown-colored outing clothes, started about 100 feet away and advanced slowly in a direct line toward the squirrels. As he came closer his movements were made slower and slower so as not to startle the animals. Sidewise movement was avoided in every possible way. The squirrel, using monocular vision, was thus less able to appreciate his approach. This method is very useful in getting close to birds or mammals in order to study or photograph them.

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The Belding Ground Squirrel escapes the rigors of the Sierran winter—when the temperature falls low and all the grasslands are blanketed in snow—by hibernating. The exact duration of the hibernation period is not known. At the Farrington ranch, near Williams Butte, one of these squirrels was obtained on April 29, 1916. In many localities individuals are out before all the snow has disappeared, and in places they have been seen to run over snow banks. At the end of September many of the animals were still abroad in Tioga Pass and on Tuolumne Meadows, even after a slight snowfall. Our latest record is of an individual out at Ten Lakes on October 6, 1915.

The only direct evidence of enemies is a note that at Tuolumne Meadows a Mountain Weasel was seen killing one of these squirrels. The weasel had the squirrel by the back of the neck. The larger high-mountain carnivores probably also levy toll on the Belding Ground Squirrel whenever opportunity offers.