Natural History of the Ground Squirrels of California/Sierra Golden-mantled Ground Squirrel
SIERRA GOLDEN-MANTLED GROUND SQUIRREL.
Callospermophilus chrysodeirus chrysodeirus (Merriam).
Other names.—Gilded Squirrel; Gilded Ground Squirrel; Copper-headed Ground Squirrel; Copperhead; Yellow-headed Chipmunk, part; Golden Chipmunk; Side-stripe Ground Squirrel; Bummer; Trinity Ground Squirrel; Callospermophilus chrysodeirus trinitatis; Citellus chrysodeirus, part; Spermophilus chrysodeirus, part; Spermophilus lateralis; Callospermophilus lateralis chrysodeirus; Citellus chrysodeirus trinitatis; Tamias chrysodeirus; Tamias lateralis, part.
Field characters.—A medium-sized, ground-dwelling squirrel with conspicuous stripes along sides of body; whole head more or less deeply yellow or coppery red; build stout; length of body without tail about 7⅓ inches, with tail about 3½ inches more.
Description.—Adult in fresh late-summer pelage: Whole top of head and hind neck, orange-cinnamon; cheek and side of neck to shoulder, ochraceous-tawny; side of snout, area around eye, ear and spot behind ear, ochraceous-buff of varying intensity; whiskers black. Two black stripes and an intervening buffy white stripe on each side of body; the whitish stripe longest, extending from shoulder over side of rump nearly to base of tail; the lower black stripe next in length, the upper shortest and it and its fellow of opposite side separated by a median band of grizzled light cinnamon-brown; this band extends from between shoulders backwards to base of tail, and expands on rump to cover flanks; side of body below lower black stripe, light buff, obscured by dusky hair-tippings. Upper sides of feet light buff; claws blackish-brown, horn-color at tips; soles of hind feet naked nearly to heel. Chin and throat and insides of forelegs and thighs buffy white; belly with hairs extensively slaty brown at base, tipped with whitish; in other words, whitish with much slaty brown showing through. Tail well-haired, flat in form, broadest in middle portion, tapering somewhat toward end; in color, as viewed from above, chiefly black, with a margin of ochraceous-buff; there is considerable mixture with cinnamon-brown toward base, however, and separation of the hairs discloses the deeper-lying hazel color of their roots; lower surface of tail centrally solid hazel, paling to ochraceous-tawny at base of tail, then a zone of black, and then an outer fringe of bright ochraceous-buff. The body side-stripes are sharply defined along their edges, but at their ends fade out gradually; also the reddish of head blends by degrees with colors of body adjacent.
Color variations.—As far as we can see there is no difference in coloration between male and female, in spite of the extraordinarily bright pattern of coloration in this species. The young, even third-grown ones, are very similar to the adults in pattern, the difference consisting only in paler tones of color, especially about the head. There is, however, considerable change in the depth of coloration with season. In the spring and early summer the head region is much paler than in late summer and fall, and there is much other evidence of fading and wear to which the pelage has been subjected. In June specimens the head is pale cinnamon-buff.
As far as we can determine from the collection of specimens studied there is but one thorough-going molt each year and this takes place in June and July. The process is gradual. The exchange of old hair for new begins first on the head and progresses backwards; but specimens often show a patchy coat, with areas of dense new hair on the head or back surrounded by old worn hair.
We are unable to make out a distinguishable race from the Trinity Mountain region, trinitatis of Merriam, 1901, p. 126, type from "Trinity Mountains east of Hoopa Valley, California (altitude 5,700 feet)." The characters assigned, of color and size, are not borne out in our large series of specimens from the Trinity region as compared with series from the northern Sierra Nevada. There is, however, a slight tendency towards paling of colors in chrysodeirus at the southern end of the Sierra Nevada and along their east flank; for example, as shown by specimens from the east declivity of Kearsarge Pass, west of Independence. This modification is evidently in the direction of perpallidus.
Measurements.—Average and extreme measurements, in millimeters, of twenty full-grown specimens from the west slope of the high central Sierra Nevada are as follows: Ten males: total length, 272 (253–290); tail vertebræ, 89 (75–104); hind foot, 41 (38–43); ear from crown, 15.7 (11.0–19.0); greatest length of skull, 44.0 (42.2–46.2); zygomatic breadth, 26.6 (25.2–28.2); interorbital width, 10.4 (9.5–11.1). Ten females: total length, 266 (243–285); tail vertebræ, 83 (67–100); hind foot, 41 (39–44); ear from crown, 16.1 (13.0–21.0); greatest length of skull, 42.7 (41.0–44.1); zygomatic breadth, 25.9 (25.0–27.1); interorbital width, 10.3 (9.2–11.0).
It would appear from the above figures that in males the tail averages a little longer than in females. The skulls of old individuals, particularly males, relative age being estimated by degree of wear on the crowns of the molar teeth, show greatest size, particularly as regards zygomatic breadth and heaviness of rostrum. Old skulls also show wider brain-case, broader jugals, and stouter postorbital processes.
Weights.—Average and extreme weights, in grams, of twenty full-grown specimens from the west slope of the high central Sierra Nevada are as follows: Ten males, 181 (155–218); ten females, 199 (136–245). Averages, in ounces: males, about 6½; females, about 7.
The heaviest example (245 grams) was a pregnant female. Males average heavier in the fall, when they are fat, than in early summer.
Type locality.—Fort Klamath [mountains near], Klamath County, Oregon (Merriam, 1890, p. 10).
Distribution area.—Upper coniferous belt (Canadian and Hudsonian life-zones, less commonly down into Transition) along the Sierra Nevada, south as far as Cannell Meadows, in extreme southern Tulare County; north through the Mount Lassen country to Mount Shasta, and thence west through the Trinity, Scott and Salmon Mountains (Mus. Vert. Zool.) to extreme eastern Humboldt County (Merriam, 1901, p. 126); also on the Siskiyou Mountains, along the Oregon border of western Siskiyou County (Merriam, 1901, p. 126); on the mountain mass to the south of the Trinities, in the vicinity of Yolla Bolly Mountain, where Humboldt, Tehama and Mendocino counties adjoin; and on the Warner Mountains, in eastern Modoc County (Mus. Vert. Zool.). The range of the Golden-mantled Ground Squirrel in northern California is probably less continuous than indicated on the map (fig. 24), there being sequestered colonies on detached mountains along with similarly isolated representations of other boreal animals and plants.
Altitudinally, this squirrel extends regularly to above timber-line, where the mountains are high enough for this, and downwards to the lower edge of the chinquapin belt, that is, scarcely as far as the yellow pines or Douglas firs. At the farthest south, in the Mount Whitney region, it has been noted as high as 11,800 feet, while downwards it was not seen below 7,000 feet. In the latitude of Yosemite, the highest point at which it was observed was 10,700 feet, and the lowest, Merced Grove of Big Trees, 5,500 feet. In the Trinity region, the lowest occurrence noted was at 4,500 feet altitude. There is thus a notable lowering of altitudinal limits with increased latitude.
Specimens examined.—A total of 259, from the following localities in California: Modoc County: ten miles northwest of Canby, 1; Sugar Hill, 11; Parker Creek and North Fork Parker Creek, Warner Mts., 9; Warren Peak, Warner Mts., 7; Dry Creek, Warner Mts., 1. Siskiyou County: head of Little Shasta River, northeast base Goose Nest Mt., 2; Mount Shasta, 10; Kangaroo Creek, 1; Wildcat Peak, 3; Jackson Lake, 5; Saloon Creek Divide, 11; Castle Lake, 2; head of Rush Creek, 6; South Fork Salmon River, 8. Trinity County: Bear Creek, 11; North Fork Coffee Creek, 3; head of Grizzly Creek, 5; one-half mile south of South Yolla Bolly Mt., 3. Lassen County: Eagle Lake, 2; Horse Lake, 1. Tehama County: two to four miles south of South Yolla Bolly Mt., 19; Mount Lynn, 2. Plumas County: Mohawk, 1. Sierra County: near Sierraville, 1. Nevada County: Independence Lake, 5. Placer County: Tahoe Valley, 2; Cisco, 13; two miles west of Soda Springs Station, 1. El Dorado County: Mount Tallae, 1. Mono County: Leevining Creek, 1; Walker Lake, 1; Bloody Canyon, 1. Tuolumne County: Ten Lakes, 1; Glen Aulin, 1; Tuolumne Meadows, 4; head of Lyell Canyon, 2; Aspen Valley, 2. Mariposa County: Vogelsang Lake, 1; Porcupine Flat, 3; one mile east of Merced Lake, 1; near Mono Meadows, 2; Mount Clark, 1; Merced Big Trees, 5; East Fork Indian Canyon, 1; Chinquapin, 3. Inyo County: Little Onion Valley, 1; Onion Valley, 4; Hockett Trail (near Carroll Creek), 2; Little Cottonwood Creek, 4; Cottonwood Lakes, 6. Fresno County: Kearsarge Pass, 5; Bullfrog Lake, 8; Bubbs Creek, 1; Horse Corral Meadow, 2. Tulare County: Siberian Pass, 1; west slope Cirque Peak, 1; Whitney Creek, 3; Whitney Meadows, 13; west slope Olancha Peak, 1; Dry Meadows, 1; Monache Meadows, 7; Jackass Meadows, 14; Sirretta Meadows, 3; Cannell Meadows, 5.
Of all our ground squirrels the Golden-mantled is the most brilliantly colored. This rather bookish name for the animal is a translation of the scientific name of the species, chrysodeirus; the more commonplace appellations locally employed, "Copperhead" or "Yellow-headed Chipmunk," serve just as well to set forth the conspicuous feature of coloration. Because of the bright colors and especially the striping of the body (see fig. 20d), this ground squirrel is often called "chipmunk;" but the latter name applies to a quite different group of animals which are slenderly built, agile, with long tails, and more numerous body stripes which involve the head as well as the body.
Fig. 24. Map showing California distribution of the golden-mantled and antelope groups of ground squirrels. The spots represent localities from which actual specimens have been examined.
the animals are to be seen scurrying across open spaces to their burrows, just in front of the mouths of which they almost invariably stop a moment before plunging out of sight, displaying then to full advantage their color pattern. If the observer traverses their domain quietly, he may suddenly discover individual squirrels intensely observing him from perches on the tops of boulders or logs. There they sit in unostentatious, hunched-over postures, blending so well with the background that they are often passed by altogether unnoticed. The element protecting them from observation most, at such times, seems to be their faculty for keeping absolutely still.
Rarely do Golden-mantled Ground Squirrels assume the upright picket-pin pose so characteristic of some others of the species. They most often maintain crouching attitudes when at rest. When running, the gait is clumsy, as compared with the chipmunks usually to be seen close at hand. The tail is rather longer than in others of the smaller sized ground squirrels, and is more conspicuously displayed, often up over the back, or, when running, either held vertically or frisked violently fore and aft. This squirrel seems to be, as a rule, almost devoid of voice. As far as our own experience has gone, there is only a single chirp of alarm, not loud nor high-pitched, and even this is uttered but rarely. One observer (W. P. Taylor, MS) has been fortunate enough to run across a talkative individual. This animal was watched as it sat bolt upright on a log uttering a "sharp call note, to-chick, sometimes varying this to tachack, p'r'r'r'r." A "general squirrel-like quality" was ascribed to these notes. At each utterance a violent flirt of the tail was given.
Speaking of habitat again, the Golden-mantled Ground Squirrel shows decided preference for rocky slopes or forest floors littered with logs, but at the same time without heavy undergrowth. Open ground is preferred; yet it keeps out of large grassy meadows, save as visiting the margins of these where they adjoin the woods. Again we see adjustment so that each of the different kinds of rodents keeps to a separate forage area without undue waste of energy in competing with another. In the higher, rougher parts of the mountains we have often found the Copperheads inhabiting rock slides. Here, as in the other places, where there are logs or scattered rocks, the object appears to be to secure protection for their burrows, so that these can be located beneath heavy objects and thus prove difficult or impossible for badgers, coyotes or bears to dig out.
The mouths of the burrows vary in diameter from 2 to 2½ inches, and the direction taken is usually steeply down into the ground for a foot or more. Unfortunately, we have never availed ourselves of an opportunity to dig out the burrow system of a Golden-mantled Ground Squirrel. We infer it to be simple and relatively short, for two reasons: the mounds at the mouths of the burrows are usually small in quantity of earth composing them; and the big roots, logs or rocks beneath which the burrows in practically all cases lead, would seem to do away with the need of an extensive and deeply penetrating system so as to secure safety from enemies which pursue their prey by digging.
The Golden-mantled Ground Squirrel is a spermophile in the truest sense of the word; it is preëminently a gatherer and eater of seeds, and most of its time aboveground seems to be occupied in diligent search for this sort of food. The cheek-pouches in this squirrel are developed to a maximum degree, and it is no uncommon thing to see an individual returning to its burrow from a foraging expedition with its two pouches so distended with seeds that the head seems double its ordinary width. We have counted 636 seeds from the two pouches of one squirrel.
Some seeds identified in cheek-pouch contents saved are: Goose grass (Galium aparine), rice-root lily (Fritillaria sp.), pentstemon (Pentstemon azureus), and silver pine (Pinus monticola). In the late summer and autumn months great activity is shown in garnering chinquapins, and there seems good reason to believe that large stores of these and various seeds are then housed away in the ground for use the following spring when the animals come out of hibernation and food is difficult to find otherwise. One individual had its cheek-pouches crammed with fragments of a brown-colored fungus such as forms bracket-like outgrowths on the bark of dead trees and old logs. Our experience shows this article of diet to be much sought after by members of the squirrel tribe generally.
Then, too, the Golden-mantled Ground Squirrel eats meat, and even carrion, as we can testify from the persistency with which our meat-baited steel traps set for coyotes and other carnivores are sprung by the Copperheads. Indeed, it seems reasonable to infer that this ground squirrel would lose no opportunity to appropriate to its use the dead remains of any sort of animal. Around camp sites we have often received good evidence of the omnivorous nature of the Copperhead's diet from seeing them gathering the scattered barley from the ground where the horses had been fed and then gleaning the scraps of cooked meat as well as bread crumbs from our own table near by. In one case a "Callo" came again and again to gnaw at a bacon rind. The young, but a third grown, show almost as much industry in carrying away food as do the adults.
That not all the food gathered, over and above what is immediately eaten, is carried to some definitely located storehouse, is shown by an observation by W. P. Taylor (MS). On the summit of Cloud's Rest, Yosemite Park, a "Callo" was encountered which was so used to the almost daily visits of people as to have become remarkably tame. It would run up to within three feet of a person, take the dried fruit thrown down for it, stuffing its cheek-pouches to capacity, and then run off just a little ways. After digging out a little hollow in the ground with its front feet, it placed the fruit therein and proceeded to cover it up with earth, using its front feet again. Sitting over the spot, it reached out to gather in additional loose stones until the cache was effectually concealed. Such hiding places as these are probably used only temporarily, at times when an abundance of food is suddenly available, to be stowed safely from someone else's reach as soon as possible, and later reclaimed for more permanent salvage.
The young are born mostly in July, but as early as the last of June at the lowest altitudes of occurrence, and as late as the first week of August up near timber line. Young one-half grown were taken on Cannell Meadows, 7,500 feet altitude, Tulare County, on July 7, 1911; and young but a third grown were taken at Cottonwood Lakes, 11,000 feet, near Mount Whitney, August 31, 1911. These dates are the extremes in the considerable series we have for time of appearance of young. Young come above ground when they are as small as one-fourth adult size (as determined by weighing). There is but one litter each year. This probably averages close to five in number. Six females captured along the central Sierras, of dates June 12 to 28, contained 5, 2, 5, 6, 6 and 5 embryos, respectively. The number of mammæ (represented by nipples) is either four pairs or five pairs, but this number is not, as some persons think, any index to the number of young born.
The enemies of this squirrel probably include most of the carnivores of the higher mountains. Hair of a "Callo" was found in the feces of a Mountain Coyote (Canis latrans lestes) in the Yosemite National Park. Near Monache Meadows, in the Sierras of eastern Tulare County, one of the writers saw a Mountain Weasel (Mustela arkonensis) in full pursuit of a "Callo" across open ground in the full sunshine of the bright forenoon of August 4, 1911. The squirrel was overtaken by the weasel, and what happened transpired so swiftly that no details were observable. A gunshot terminated the episode, and the "Callo" was found already stone dead, with two tooth-punctures on each side of the nape of its neck.
The Golden-mantled Ground Squirrels hibernate regularly. They doubtless construct warm, dry nests underground, as individuals have been seen gathering soft materials and carrying these to their burrows. In one instance an individual was seen to pick up a piece of brown paper and after tearing it with its teeth and forepaws, stuff it into its cheeks and disappear into a burrow (C. L. Camp, MS). By the last of August these ground squirrels begin to acquire fat, and during September and October they are simply "rolling in butter," as the saying goes. This seems to be in preparation for their long period of dormancy, which extends from the last of October to the middle of April.
Exact dates of going into, and coming out of, their winter sleep are not available to us. But in the Yosemite region in 1915 individuals were seen abroad in the Canadian life-zone commonly up to October 18; on October 30, in the same zone, but two individuals were seen on the same ground where very many were noted a month previously; and none at all were seen on subsequent dates when they were looked for at suitable altitudes. The estimate of April 15 as near the time of reappearance in the spring is based on what we have been told by trappers and forest rangers, and their statements were only from memory.
Since the territory inhabited by the Golden-mantled Ground Squirrel is practically altogether above the altitudinal limit of cultivation by man, this species rarely figures as anything worse than a camp-robber or "bummer" (see fig. 20d). We have heard packers complain of its proclivities in the way of carrying off grain or provisions from summer camps in the higher mountains. But the total destruction of property thus wrought can hardly be formidable, and compensating for it to some degree must be counted the added animation lent to the mountain scene by the presence of these pleasing rodents.