Yosemite > Library > Handbook > Mammals >

Some Mammals of Yosemite National Park

Handbook of Yosemite National Park (1921)
by Joseph Grinnell and Tracy Irwin Storer

Next: Reptiles and Amphibians of Yosemite • Contents • Previous: Birds of Yosemite

SOME MAMMALS OF YOSEMITE NATIONAL PARK

By Joseph Grinnell, Director, and Tracy Irwin
Storer, Field Naturalist, Museum of Vertebrate
Zoölogy, University of California

(Contribution of the Museum of Vertebrate Zoölogy of the
University of California)

The Yosemite region possesses an abundant population of mammals both as to species and individuals. A total of ninety-seven different kinds is definitely credited to the region. Subtracting three species known to be extinct, and eight varietal forms, we have record of eighty-six "full species" now to be found between Snelling and Mono Lake. The determination of the population as to individuals is more difficult with mammals than with birds, and has been attempted in only a few places. In so far as data have been assembled it is estimated that mammals exist throughout the country at large in the ratio to birds of ten to one.

The average visitor, nevertheless, sees much less of mammals than of birds. Squirrels and Chipmunks are out during the daylight hours, and occasionally a Bear or Coyote or a group of Deer is observed, but the presence of most other mammals must be ascertained by noting their "sign," tracks, and workings. Footprints of Badgers, Wolverines, and Mountain Lions may be seen in trails and roadways, or on snow; gnawed tree trunks give evidence of Porcupines; and earth mounds of different sorts indicate the presence of Moles and Gophers; but the host of small species of Mice and Shrews leave less evidence of their presence than any of the above, and only assiduous trapping (which can be done in the park only under special permit for scientific purposes) will reveal the abundance and variety of mammalian life which is active during the hours of darkness.

Among all this multitude of mammals there is not one species which need be feared by visitors on the ground of personal violence. Bears in search of food will sometimes raid camps at night, especially when the occupants are away, and Mice and Chipmunks will gnaw into stores of provisions, but these temporary inconveniences, if they are experienced at all, are certainly far more than offset by the pleasure to be gained in observing the ways in which these diverse types of animals carry out their several existences.

The California Gray Squirrel will be one of the first mammals to attract the attention of the visitor to Yosemite, for it is fairly well represented in the Transition Zone forests which are traversed by the several roadways leading into the mountains from the west, and it is common among the trees on the floor of Yosemite Valley. The Gray Squirrel is typical of the tree dwelling members of the squirrel family. Its lithe body, strong legs, and long, heavily bushed tail all enable it to jump readily from branch to branch, while the sharp curved claws enable it to cling securely to the bark of trunk or branches. The Gray Squirrel is active practically throughout the year, so that visitors at whatever season will see the species; however, more individuals are out in good

PLATE X Rocky Mountain Mule Deer, the only species of hoofed big game now to be found in Yosemite National Park. Photo from habitat group, California Academy of Sciences, San Francisco

At other times of the year the Gray Squirrel lives on a variety of vegetable materials, especially upon acorns, many of which are buried in the ground in the fall. In the spring it sometimes turns its attention to the eggs and nestlings of birds which nest in trees. The birds recognize the squirrel as a possible enemy and are quick to set up a disturbance whenever a Gray Squirrel appears in the near vicinity of their nesting precincts.

The Gray Squirrel population in Yosemite Valley seems somewhat larger than in like territory elsewhere. This may be due to the additional food available about houses and camps as well as to the abundance of oaks and yellow pines there. An estimate made in Yosemite Valley during October, 1914, placed the numbers of the Gray Squirrel at one per acre. The Valley, below the 4250-foot contour, and from "The Gateway" below Cascades eastward, contains about seven and a half square miles. This would give a total Gray Squirrel population, in the fall, of 4800, which is believed to be considerably in excess of the numbers to be found in any equal area in the open woods of the Transition Zone elsewhere.

In the forests of the Canadian and Hudsonian zones lives the Sierra Chickaree, a "red" squirrel similar in general habits to the Gray Squirrel but of smaller size and different coloration. The Chickaree is dark brown tinged with reddish on the upper surface, has a black line along each side of the body, and the lower surface of the body is white or buffy white. Its body is about eight inches long and the moderately bushy tail five or six inches. The mode of life of the Chickaree is similar to that of the Gray Squirrel. It is a dweller in the trees and comes to the ground only when necessary to retrieve a fallen cone or to cross an opening not bridged by overhead branches. Where trees are close together as in many parts of the lodgepole pine forest the Chickaree literally lives in the trees.

The food of this species is similar to that of the Gray Squirrel but not so varied; there are no large oaks and but few nut producing plants within the Chickaree’s domain. It must perforce live more extensively on the seeds of cone-bearing trees. The Chickarees which dwell in the Canadian Zone where firs are abundant may be seen in the fall assiduously gathering the thin-scaled cones of the red and white firs. These are "cachéd" by being buried along the sides of some large log near the squirrels’ home tree. When the snow comes the cones gain further protection, in cold storage as it were, whence they are drawn upon and used by the Chickaree, as need be throughout the winter. In the spring observant travelers will find the logs strewn with the scales and cone-cores discarded by the squirrels during their meals. The voice of the Chickaree is decidedly different from that of the Gray Squirrel and is also much more varied. One common call is a prolonged trill of high pitch; and there is a striking single note which is given from time to time with an insistent delivery.

There are seven species of small striped Chipmunks in the Yosemite section, and five of these occur within the Park boundaries. All agree in general pattern of markings, having the head and back marked with alternate stripes of dark and light color and with more or less bright brown along the sides, but there are decided differences in tone of coloration. There are also considerable differences in size, habits, and local distribution of the several species.

Chipmunks in general are nimble creatures, to be seen scurrying about in their eager search for food, at frequent intervals playing with one another or fleeing from supposed or real enemies. There is a distinctive sort of quick intermittent or "jerky" movement on the part of a chipmunk, in which the animal will move a few steps and then be absolutely still for several seconds, save perhaps for a sideward switching of the bushy tail. In these short intervals of quiet the streaked pattern fairly melts into the animal’s surroundings so that the eye may lose the creature for the moment altogether. Sudden changes of position are often each accompanied by a single exclamatory note. If a Chipmunk becomes thoroughly frightened it makes off pell-mell and in direct course toward its retreat, scarcely looking behind, and uttering a torrent of excited chippings as it goes.

The usual note with all of the species is a high pitched psst which is often repeated to form a sputtering series. The larger species have also a hollow low-toned pook which may be likened to the bark of a dog, as it is given with rather long rests between successive notes.

Each species of Chipmunk has a definite general range and a particular "niche" within this range; no two species are found in exactly the same surroundings. On the west slope of the mountains in portions of the Upper Sonoran and Transition zones containing mixed chaparral and trees there is the Mariposa Chipmunk (Eutamias merriami mariposae) a large dark grayish species. It is found in small numbers in thickets along the north and south walls of Yosemite Valley. The most widely distributed and commonest species of the Yosemite region is the Tahoe Chipmunk (Eutamias speciosus frater) which occurs throughout the Canadian and Hudsonian Zones. It may be known at once by its small size (total length about eight inches), bright highly contrasted pattern of coloration, extremely lively manner, and especially by

PLATE XI Mountain Lion or Cougar Photo from habitat group, California Academy of Sciences, San Francisco

The Canadian Zone possesses also a rather large species of predominantly grayish coloration, the Allen Chipmunk (Eutamias senex). This one lives about boulders, fallen logs, and brush patches. In the upper part of the Transition Zone and the lower portion of the Canadian there is a species of about the -same size and practically the same habits as the preceding, but with much taller ears and a conspicuous white spot at the hinder base of each ear. This is the Long-eared Chipmunk (Eutamias quadrimaculatus), almost as brightly colored as the Tahoe Chipmunk. The smallest and palest-colored species within the park is the Alpine Chipmunk (Eutamias alpinus) which dwells among rocks and fallen trees in the Hudsonian Zone. It is the timberline chipmunk, the last to be seen during an ascent of Mount Lyell or any of the other loftier summits.

All of the chipmunks living above the snow-line (about 3300 feet) in the Yosemite section hibernate for longer or shorter periods of time in winter, although their larger relatives, the Gray Squirrel and Chickaree, are active throughout this season, retiring only on very stormy days.

There is one member of the squirrel tribe which is observed by very few Yosemite visitors. This is the strictly nocturnal Sierra Nevada Flying Squirrel, the only local mammal except the bats which is able to travel through the air. The word "flying" is here used inaccurately, as this squirrel is only able to volplane from a high perch to a lower one. Its body is flattened, and between the fore and hind leg on each side there stretches a furred double layer of skin which adds to the animal’s spread and makes feasible its oblique passage through the air. Its dense silky hair seems to be an adaptation in this direction and also contributes to the quietness of its "flight." The Flying Squirrel lives in the Transition and Canadian Zones, being fairly common in the black oaks in Yosemite Valley and in the red firs above the Valley rim.

All of the members of the squirrel kind mentioned in the preceding paragraphs are species which live and find shelter chiefly or entirely in trees or logs; but there are also important members of the group which dwell upon and beneath the ground. These are the Ground Squirrels and the Marmot. The California Ground Squirrel, of brown tone of coloration with whitish shoulders, is in habits the western counterpart of the Prairie Dog and is found, in the Yosemite region, from the San Joaquin Valley up to an altitude of 8200 feet in the mountains. In the Canadian and Hudsonian zones is the Sierra Golden-mantled Ground Squirrel, locally called "copperhead." This species has the head and shoulders golden yellow while the body is marked along each side with two jet black stripes enclosing one of pure white. The "niche" of this species is in the open forest about bases of large trees and rocks. The Hudsonian Zone supports another burrowing species, the Belding Ground Squirrel or "picket-pin," a rather plainly garbed animal of yellowish brown coloration and with a reddish wash along the back. It lives altogether in the meadows where it finds abundant forage during the summer months and where it may often be seen sitting up in characteristically erect posture on the lookout for danger.

The Golden-mantled and Belding Ground Squirrels hibernate regularly and so do those representatives of the California Ground Squirrel which live in the Transition and Canadian zones where snow lies on the ground during the winter months. All of these rodents feed to repletion during the summer and by fall their bodies are heavily stocked with fat which then serves to warm and nourish them during the long winter sleep.

The Sierra Marmot (Marmota flaviventer sierra), often called "Woodchuck," is the largest local representative of the squirrel family in the Yosemite region. In bodily configuration the Marmot is stouter than the other members of the family, with proportionately shorter legs and tail. It is not infrequently mistaken for the badger, a totally different animal which, however, often lives in the same sort of country. Adult Marmots measure 15 to 18 inches (head and body), with the tail 5 to 8 inches long, while the weight ranges from 4 to 6 3/4 pounds with different individuals. Here in the Sierras the Marmot is a high mountain animal, dwelling chiefly in the Hudsonian Zone. The winter months (from about October until May) are spent in hibernation. Each Marmot has a burrow in the ground, usually beneath some huge granite bowlder at the edge of a meadow or at the base of a tree at the margin of the forest. On all pleasant days the Marmots are out during the warmer hours, either foraging in the grass of the meadows or resting near their burrows. During the summer months the Marmots must eat not only to supply their daily needs but also to take on fat to carry them through the long winter. It is not an uncommon experience during this season to come upon one of the animals out some distance from its burrow and busily engaged in cropping the new grasses. If frightened while so engaged the Marmot will make off with a lumbering gallop toward its burrow. When not feeding, the animals spend much time sunning themselves on the tops of bowlders or at the mouths of their burrows. In any situation, when alarmed, the Marmot utters a shrill bark or whistle. Sometimes it stands up on its hind legs to get a better view of the object which it is keeping under surveillance.

The Rocky Mountain Mule Deer (Odocoileus hemionus hemionus) is the large mammal most likely to be seen by the Yosemite visitor. In early days, when white pen first thronged the Sierran foothills in search of gold, no less than four species of homed or antlered big game animals inhabited the Yosemite region. The San Joaquin Valley marshes supported the Tule or Dwarf Elk; the plains both east and west of the Sierras were the ranges of the American Antelope; the high Sierran crest was the habitat of the Sierra Mountain Sheep, while on the intervening slopes of the mountains there lived the Mule Deer. The first three have vanished from the Yosemite section, probably never to return, but the Deer are still present in goodly numbers. Deer are present in the park throughout the year, though their local distribution changes with the season. In the summer time they are more common in the higher zones and many are to be seen at Chinquapin, above Yosemite Falls and in the vicinity of Merced Lake, and a few wander above timberline along the Sierran crest. With the

PLATE XII American Black Bear amid the yellow pines in Yosemite Valley Photo by J. T .Boysen

The Mule Deer gains its name from the large size of its ears, which are about eight inches long and four inches across. The tail lends further character to the suggested comparison, for this member is slender and nearly devoid of hairs . toward the base beneath. In the summer months the Deer wear a thin reddish colored coat, which is acquired in June and carried until October; then the thick gray pelage of winter is assumed.

The fawns of the Mule Deer are born about the first of July, but the does keep their charges hidden until a month or so later, after which time the young in the spotted reddish coats are seen rather commonly. The usual number at a birth is two, though single fawns are often seen and rarely there are three young. The young run with the mother until the following spring or until they are "yearlings." Then she deserts them to prepare for the new litter. The Deer in the park have responded favorably to protection from hunting, and large bands are seen there during the winter months. Some pass through Yosemite Valley but the larger migratory movements are along the ridges above.

Discussion of Deer leads logically to mention of their principal enemy, excepting man, the Mountain Lion or Cougar. Save for the Wild Cat or "Lynx Cat" (two names for one and the same species) there is no other member of the cat tribe here; there are no Canada Lynxes in the Sierra Nevada. The Mountain Lion when fully adult measures about 6 1/2 feet from tip to tip, of which about thirty inches is the tail. The body coloration is usually reddish brown, sometimes gray. The only difference between males and females is in size, the former being the larger. Mountain Lions are so wary that but few are seen under ordinary circumstances. Many persons have lived in the mountains for years without seeing one of the animals. Only when trailed and treed by dogs are they to be seen readily. However, evidences of their presence and activity are relatively common. Their tracks are seen in summer along dusty trails or crossing roads, and rather commonly after the snows of winter come. The footprints are catlike, and measure from three to four inches in each surface dimension. The depredations of the Mountain Lion among the Deer are most evident during the winter. In that season the deer are concentrated in the foothills at the margin of the heavy snow, and then the Cougars have a relatively easy time to obtain prey.

Another "predatory" mammal, common in the high Sierras and likely to be seen by visitors to the park, is the Mountain Coyote (Canis latrans lestes). Standing about 20 inches high at the shoulder with a body length of 30 to 33 inches, with ears about 4 inches tall, and weighing as much as 25 pounds, some particularly long-haired and gray colored individual Coyotes are designated as "gray wolves" by local trappers. All efforts, however, to obtain actual specimens of the real wolf have been unavailing. The Mountain Coyte is less restricted in diet than the Cougar. It feeds upon a variety of small game such as ground squirrels and gophers, and even at times captures insects; manzanita berries are also eaten in season. Coyotes sometimes feed upon deer, but their "venison" comes mostly from carcasses left by the Mountain Lion. The barking of the Coyote is often heard in the mountains and the combination of yelps, squeals, and howls in the voice of an individual often gives the impression that there are several rather than a single animal.

Bears there are in the Yosemite, even close about the floor of the Valley. Indeed, the word Yosemite, of Indian origin, means big bear or grizzly bear. If ever there were grizzlies in Yosemite Valley, as there were certainly at other points in the region such as Wawona, none are left to-day. The famous grizzly with its huge size, long front claws, and "silver-tipped" fur is extinct here now, but its smaller tree-climbing relative, the Black Bear, is still thriving in goodly numbers. These smaller bears exhibit two color phases, some individuals being black, others cinnamon; and litters of cubs have been seen in which one individual of the two was black and the other cinnamon colored. The name "brown bear" properly applies to a species not found here. The Black Bear is found throughout the Transition and Canadian zones of the park and is likely to be seen, from June until October, by visitors to the Yosemite Valley and adjacent points. The various garbage dumps which have been established in the Valley attract the bears regularly in the night time. Several bears have had their headquarters in the rock slides near El Capitan from where they can fare forth and hunt for food in the table and kitchen débris. Under native conditions they eat berries and seeds, beetles, ants, and other insects, and small mammals; the wide variety of their likes in the matter of food places much material within easy reach. In October or early November the Bears seek some secluded cavern or hollow tree and curl up there for a sleep which lasts until early the following spring. Persons camping out in the mountains are sometimes disturbed by having their provisions raided- by bears, but there are no instances known to us in which anyone has been injured by a bear when the start of the trouble did not lie with the person concerned.

There are numerous species of smaller carnivores in the Sierras of the Yosemite region. Many of these will be recognized at once as among the important "fur-bearing" species. About the rock slides of the Hudsonian Zone is the brownish colored Sierra Pine Marten (Martes caurina sierrae); in the forests of the Canadian and Hudsonian zones is found the Pacific Fisher (Martes pennand pacifica), a much larger animal of generally similar build with a long bushy tail and much black in its pelage. In the highest parts of the mountains there is the Sierra Nevada Wolverine (Gulo luscus luteus), a heavy-bodied animal of yellow and brown coloration, now rare. About the buildings in Yosemite Valley and around rock slides in the higher mountains the Mountain Weasel (Mustela arizonensis) occurs in considerable numbers. The Weasel has a slender body, scarcely two inches through but nine or ten inches in length. The body color is yellowish brown in summer, but this changes to white in the winter season. The end of the long and slender tail remains black at all seasons so that in winter pelage our Weasel is an "ermine" in general appearance.

PLATE XIII Three notable animals of Yosemite National Park The California Grey Squirrel (upper), Tahoe Chipmunk (middle), and Pacific Rattlesnake (lower) Photos of squirrel and snake by J. T. Boysen, Yosemite; Chipmunk by J. Dixon, California Museum of Vertebrate Zoölogy

The predacious mammals considered thus far are all of considerable size, but there are "hunters" of smaller bulk though no less daring or active in their pursuit of prey.

The rocky shores of the streams and crevices beneath logs and brush constitute the forage ground of several small species of animals called Shrews. These are related to the moles, and may be known as a group by their long slender noses, long tails, and their short smooth fur. These small predators, most of which are less than two inches in length of body, are voracious feeders, to judge from their habits in captivity; their presence in a region suffices to explain why bodies of small birds or mammals disappear so quickly When trapping in localities where Shrews abound it is not an- uncommon experience to have specimens caught during the early hours of the night, half devoured by morning.

Bats are present in most of the region, whence at least eight species are now known. Certain species are restricted to the warmer valleys and foothills, others occur over the floor of the Yosemite gorge, and one species, the High Sierra Bat, has been taken at 10,350 feet altitude near Vogelsang Lake, almost the highest altitudinal record for any species of bat in this country.

Many of the larger accomplishments in nature such as the felling of large trees by storms, the scouring of valleys by freshets, or the results of earthquakes, are spectacular in the extreme; but other highly important operations are carried on in such an unobtrusive manner that they excite no popular interest or comment. The actions of Gophers and Moles and other burrowing animals as agents of erosion and soil manufacture are examples in this latter category. In cultivated districts the Pocket Gophers are looked upon as unmitigated nuisances, but their rôle in the mountains is totally different. The numerous earth mounds and tunnels made by Gophers play an important part in pulverizing and aerating the granitic soil and permitting water to permeate below the surface. The fine surface material is washed down by the melting snows and the summer rains to add to the fertile plains of the great valleys. During the summer the Gophers push the loosened soil from below ground out on the surface; but in winter this material is packed into tunnels in the snow and these "earth cores" are to be seen everywhere in the higher mountains in early summer.

Moles likewise live most of their time beneath the surface of the ground, but their structure, and habits, and their mode of life, are quite different from those of Gophers. The Moles never appear above the surface and their earth mounds are erupted from beneath, being split with many cracks and having a rough and irregular outline. The Gopher comes to the surface with each lot of earth he has loosened and pushes it out so that eventually his mound has a crescentic rim with a low spot at one side indicating the site of the exit after closure. Moles often run along just an inch or two beneath the surface of the ground and the resulting "ridges" are plainly evident in places where the animals have been hunting actively for insects. The Mole is chiefly if not wholly dependent upon insects, worms, and other low forms of animal life, while the Gopher feeds entirely upon roots and other parts of plants.

As stated in the opening paragraph there is a surprisingly large population of small mammals, the presence of which can hardly be surmised by the casual observer. Intensive trapping shows that rock crevices, old logs, brush heaps, and the like are tenanted by large numbers of White-footed Mice of several species, all agile long-tailed rodents; the grassy meadows everywhere are the homes of chunkily built Meadow Mice with short legs and soft furry coats; and the higher meadows support many of the long-tailed long-legged Jumping Mice. In the rock slides of the higher mountains there lives the much larger Bushy-tailed Wood Rat. This animal, like its smooth-tailed house-building relative in the foothills, is commonly called "pack rat" or "trade rat" because of its habit of carrying away articles of camp equipment and often leaving in their places chips of wood, or other similar tokens. The Bushy-tail lives in the rock slides of the Hudsonian Zone, along with the Yosemite Cony and the Sierra Pine Marten. The Wood Rats exhibit some tendency toward house-building as is shown by the accumulations of twigs and sticks in some of the rock crevices, but the animals rarely do as much in this direction as the Streator Wood Rats in the Upper Sonoran and low Transition zones.

In the lodgepole pines of the Canadian Zone the work of the Yellow-haired Porcupine is to be seen in many places; more rarely the animal itself is discovered. The Porcupine scarcely needs description. It is a rodent, or gnawing mammal, of large size, weighing when adult fifteen pounds or more. The whole upper surface of the body is provided with long quills which grow out beyond the warmth-giving under-fur. These quills have very sharp points, provided with slight barbs which adhere readily to any rough or soft substance into which they are thrust, while the quills are readily released from their attachment to the skin. The Porcupine cannot "shoot" its quills as is supposed by some persons, but for defense it curls its body up so as to be surrounded by its spiny covering and its tail is lashed from side to side. Any person or carnivore incautious enough to come in contact with the quills speedily receives a number of these in its flesh. The Porcupine has one particular item of forage which it seeks at all times of year, namely the inner growing layers of the bark of the pine. A recently-fallen tree is likely to have all of its branches stripped of bark and graven with the paired markings left by the incisor teeth of the animal. But downed trees are not a necessity, for the Porcupine climbs well and often its forage is obtained well up in some large tree. The lodgepole pine with its thin outer bark seems to afford the animal the most suitable kind of forage, and where common it is eaten to the exclusion of other coniferous trees.

This brief account of the more noteworthy mammals of the Yosemite section may well close with mention of that interesting resident of the large heaps of slide rock in the Hudsonian Zone, the Yosemite Cony (Ochotona schisticeps muiri), variously called "pika," "little chief hare" and "rock rabbit." The latter two names have reference to the relationship of the Cony with the rabbits, a kinship evinced more by internal structure than external features. The Cony measures less than seven inches in length and has no obvious tail, both pairs of legs are short, and the ears are rounded. The covering of hair everywhere is dense. Its habits are unique; it runs on all fours with a hobbling gait, and does not sit up on its haunches like a rabbit. Instead of migrating to a milder climate, or else hibernating, during the winter season, the Cony keeps active even though its rock slide home is covered by many feet of snow. In summer it is busy with food-getting, and cuts, dries, and piles up in airy, yet protected places, large heaps of "hay." This includes stems and leaves from most of the common plants in the vicinity. The animals rarely forage beyond the margins of the rock slides, seeming to feel that within these heaps of tumbled granite they are afforded their only reliable protection. When not engaged in foraging the Cony is accustomed to perch on some one of its observation posts in the rock slide and there keep watch of the neighborhood. The nasal "bleating" notes are given at this time. Thus the Cony, unlike the rabbits, makes regular use of its voice.

REFERENCES

Grinnell, J., 1913. "A Distributional List of the Mammals of California." Proceedings California Academy of Sciences, 4th series, vol. iii., pp. 265-390, pls. 15, 16.

Nelson, E. W., 1918. Wild Animals of North America. (Washington, D. C., National Geographic Society: reprint with additions from National Geographic Magazine, vol. xxx., No. 5, Nov. 1916, and vol. xxxiii., No. 5, May 1918). Numerous illus.

Stephens, F., 1906. California Mammals. (San Diego, Calif., West Coast Publishing Co.), 351 pp., illustrated.

Next: Reptiles and Amphibians of Yosemite • Contents • Previous: Birds of Yosemite

http://www.yosemite.ca.us/library/handbook_of_yosemite_national_park/mammals.html