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Mammals of Yosemite National Park (1952) by Harry C. Parker


RODENTS OR GNAWING MAMMALS — Rodentia

MOUNTAIN BEAVER

From “Mammals of Lake Tahoe” by Robert T. Orr, California Academy of Sciences.

MOUNTAIN BEAVER

The Sierra mountain beaver bears no close resemblance to the true beaver. It looks much like a tailless muskrat or a gigantic meadow mouse, blackish brown in color. It will seldom be seen by the park visitor, for it utilizes extensive tunnels safely to reach food above ground and is chiefly nocturnal. The burrowings, six or seven inches in diameter, running parallel to the surface, roofless in spots, may be found on bottom land near streams in widely scattered locations at elevations ranging from less than 4,000 feet to more than 10,000 feet.

The food consists of almost any “greenery,” but bark is also eaten. Mountain beavers are known to stack and cure vegetation near the mouths of their runways. This is now believed to be done in order to have a supply of dry bedding, rather than in preparation for the season when green food will not be available.

California gray squirrel

Photo by Anderson

California gray squirrel

The California gray squirrel should be identified easily by any visitor to Yosemite Valley. Some two feet long, with a beautiful, bushy gray tail, it is adequately described by its name. The Sierra ground squirrel, which sometimes climbs trees, might be confused with this species, but the ground squirrel may be distinguished by its two white or grayish shoulder patches and the much narrower tail. The upper limit of the range here seems to correspond with that of the oaks, although gray squirrels also feed freely on pine seeds. It is thought that in the higher forests, competition from the Sierra chickaree prevents the gray from flourishing.

The California gray squirrel sometimes builds large nests of twigs, needles, grass and similar materials, in trees, or, soft linings may be made in cavities of trees. The California black oaks in Yosemite Valley are so old that plenty of holes seem to be available, for outside nests are not too common there. I have reason to believe that some individuals make an outside nest in summer, then move to a cavity with the approach of autumn. However, this cannot be positively stated to be a universal practice.

The preferred food here appears to be acorns and pine seeds. Acorns are cached individually in the ground in autumn, some of which are dug up later, especially in winter. I have seen a gray squirrel dig down through several inches of snow and successfully locate an acorn buried in the ground beneath. Perhaps this food storing habit helps explain why gray squirrels do not hibernate, but are active all the year.

Gray squirrels were virtually wiped out in Yosemite by an epidemic of scabies in the early 1920’s. They were extremely rare here for a number of years; an all-day census of the Valley in the summer of 1935 revealed but two individuals. By the early 1940’s the species had made its way back to such an extent that a. considerable number were killed by motor cars. They are now abundant throughout their proper range in the park.

Sierra chickaree

From Kodachrome by Parratt

Sierra chickaree

The Sierra chickaree is the favorite mammal of many rangers. I think they like the little fellow because he is so active and vociferous, contributing a touch of life to the still reaches of our coniferous forests. When an intruder comes quietly into the chickaree’s territory, he will hear the bird-like note of interrogation, variously described as quer-o, quir-o or whee-o. If the intruder is noisy, or startles the chickaree, the animal’s extensive vocabulary is brought into play and one is readily convinced that this animal can swear!

Visitors from the Northeast will recognize our chickaree as a species of red squirrel; those from the Northwest will realize that it is a race of their Douglas squirrel; those from the Rockies will call it a pine squirrel. About one-third the size of the gray squirrel, dark, reddish brown above with white eye-ring, whitish beneath, it is, indeed, closely related to all of those. While the lower limits of its range are at the elevation of Yosemite Valley, its chief bailiwick is the higher coniferous forests, extending up to the limit of trees.

The home of the chickaree is usually in an old rotten stub or other tree cavity. This is lined with shredded bark, pine twigs and similar materials. Chickarees are not sociable animals and have a strong sense of territory, defending it against invasion by another of their kind, in fact resisting, if only vocally, intrusion by any other creature.

Seeds in cones provide the chief source of food, although the tender buds of pine, mushrooms, nuts and even meat are not scorned. Cones are cut down while yet green. The seeds are either eaten immediately, or the cones are stored along old logs or similar crannies near the squirrel’s home. These shaded, often moist spots, provide conditions that tend to inhibit the cones from opening up so the seeds are retained until needed in the winter. Winter food is a matter of concern to the chickaree, for it is active the year around, even when snow covers the ground.

Sierra chickaree’s kitchen midden

Sierra chickaree’s kitchen midden

The harvest by one individual can reach prodigious proportions. The chickaree usually works in the tree, cutting off a number of cones, then going down to the ground and caring for them. In the Mariposa Grove of Giant Sequoias, a single chickaree is known to have harvested and stored in hollow logs, in 12 days, enough sequoia cones to fill 38 barley sacks. When it is realized that a sequoia cone is about the size of a hen’s egg, the magnitude of this feat is even more impressive.

Since the seeds are what interest the squirrel, obviously the scales and stems of cones make quite a pile of debris after its meals. A spot is usually chosen for the shucking process which provides a good lookout, such as a rock, log or old stump. Consequently the waste from many meals adds up to quite a pile of scales and sterns. These piles are known as “kitchen middens” and are readily found throughout the forested country above the rim. Gray squirrels may make similar middens, but with a greater variety of food available, such workings are not found so commonly in Yosemite.

MARMOT

From “Mammals of Lake Tahoe” by Robert T. Orr, California Academy of Sciences.

MARMOT

Daytime travelers on the Tioga Road are very likely to make the acquaintance of the southern Sierra marmot. Near or within the patches of meadowland, marmots are fond of lying flattened out on the tops of large rocks, basking in the sunshine. About the size of a cat, with its glossy, grizzled, light-brown upperparts and contrasting orange-yellow chest and feet, they make a strikingly pretty sight in this position. Easterners will note a strong resemblance to a woodchuck, for the two are closely related.

Marmot tracks. Hind foot on left, front on right. Six-inch pencil.

From cast by M. V. Hood

Marmot tracks. Hind foot on left, front on right.
Six-inch pencil.

It must have plenty of green plants to eat and rocks or trees or logs under which to burrow. Tunneling under such a place means that a predator is not able to dig them out. At the first real threat of danger, it is toward the burrow that the marmot gallops. Some of them take up residence in barren rock slides so that in case of alarm, all they have to do is tumble down into the intricate rock maze to be safe. The basking points have a great many droppings on them—elongate, dark and about one-half inch in diameter.

Heavy as it is, this gigantic ground squirrel can sit up straight on its hind legs if that is necessary to obtain a better field of vision against the possible approach of enemies. The call is a short whistle, though not as man-like as that of the hoary marmot in Olympic, Mt. Rainier and Glacier National Parks.

Our marmots tend to live in groups, but not large colonies. Like a true woodchuck, they are not active at night and they hibernate in the winter.

Belding ground squirrel

From Kodachrome by Anderson

Belding ground squirrel

The Belding ground squirrel can scarcely escape notice by the summer visitor to Tuolumne Meadows. Their piping, whistle-like calls resound on every hand and they are quite in evidence as they sit up very straight, like a stake driven into the ground, in the effort to maintain a more effective lookout for danger. This last habit has earned for them the popular name, “picket-pin gopher.” They are about the size of a house rat, but have a short, hairy tail. The upper parts are yellowish gray with a wide, reddish-brown streak down the back.

Belding ground squirrel tracks. Six-inch pencil.

From cast by M. V. Hood

Belding ground squirrel tracks. Six-inch pencil.

Belding ground squirrels are most common in our higher meadows, though meadow land is not absolutely necessary for them, so long as a good supply of grasses, herbs and their seeds is available for food.

Home and shelter are in the ground. Since winters are very long in the high country, and these animals hibernate, it can be seen that a great proportion of their lives must be spent underground. Badgers are very assiduous in digging them out. Besides predatory birds, other enemies are known to include weasels and the mountain coyote.

The antics of Beldings are interesting to watch, for they are very active. When the young first appear above ground, they remain in the vicinity of the hole, while the mother mounts guard to give the alarm in case of danger. As the season progresses, the youngsters go forth on their own and dig individual burrows for themselves.

Sierra ground squirrel. Albino in rear.

Photo by Anderson

Sierra ground squirrel. Albino in rear.

Most Californians coming into the park will have no difficulty in recognizing the Sierra ground squirrel. More than likely they will have some race of Citellus beechcyi near their homes, for the species is widely represented in the State. The Yosemite form has been set apart from the California ground squirrel of the coastal region because of the more grayish appearance of the former and for other technical differences. The whitish shoulder patches, upper parts speckled with grayish white and the fairly bushy tail serve to separate the Sierra ground squirrel from any other Yosemite digger. The distinctions between it and the California gray squirrel have been mentioned (p. 64).

This animal dwells in a system of underground tunnels made in open situations. When alarmed fully, the ground squirrel will literally fall into the nearest entrance it can reach. It sometimes sits very erect, presumably to widen the field of vision. It is active only in the daytime.

The food consists of seeds, grasses, fruits, plants, roots, bulbs, acorns, and some meat. It has internal cheek pouches which are filled when it is gathering and carrying food. It may climb into certain trees and low shrubs in connection with the search for food.

The Sierra ground squirrel is a hibernating animal. However, the hibernation must not be too profound, for I have often seen them abroad in Yosemite Valley during prolonged warm spells in January. After the weather again became severe, they were never seen about until the next warm spell.

Young golden-mantled ground squirrel. Note absence of facial stripes.

Photo by R. G. Beidleman

Young golden-mantled ground squirrel.
Note absence of facial stripes.

The Sierra golden-mantled ground squirrel is the most beautiful of the Yosemite ground squirrels. The head, neck and shoulders are a reddish or coppery yellow, forming the “mantle,” while two white stripes run along the sides of the blue-gray back. These stripes lead some people to confuse them with the chipmunks. However, the golden-mantle is larger than any chipmunk, about two-thirds the size of the Belding, and does not have stripes running through the face.

Golden-mantled ground squirrels are common in the open forests of the middle elevations, such as are found along the Tioga and Glacier Point Roads and the trails along the rims of the Valley. They make short burrows under ground, with the entrance near a log, stump or rock which provides a lookout point.

The food consists of nuts, fruits, and other vegetable matter, varied with meat. There is some evidence of food storage, though this must be for early spring use, since the Sierra golden-mantled ground squirrel hibernates.

Visitors to Glacier Point once came to know this species well. The golden-mantles there were unafraid of humans and permitted close approach, especially when food was offered. Sometimes they even crawled over a person’s clothing and searched the pockets for food to stuff in their capacious cheek pouches.

However, a few cases of relapsing fever were traced to Glacier Point several years ago, and since golden-mantled ground squirrels are hosts to the tick that carries the fever, it has been necessary to reduce the population at that place and proscribe the sale of peanuts and other delicacies relished by ground squirrels.

It should be remembered that it is never advisable to come in close contact with any ground squirrel in the West, because some of them do have certain parasites which may carry diseases to which humans are susceptible. This does not mean that every ground squirrel needs to be exterminated. Public health authorities are well equipped to determine when a territory is dangerous and to prescribe measures to be taken in such an area. We have been assured by them that there is no cause for alarm at Glacier Point under the present precautionary program.

Long-eared chipmunk. Note the prominent eye-stripes found in true chipmunks in the West.

Photo by R. G. Beidleman

Long-eared chipmunk. Note the prominent
eye-stripes found in true chipmunks in the West.

Chipmunks are captivating mammals to watch. Their bright pattern, lively habits, and bird-like calls can afford hours of pleasure to the visitor who remains very still while in their haunts. There should be no trouble recognizing them as chipmunks by the fact that the stripes include the face and there is a narrow, dark stripe down the center of the back. The sharp, pointed nose and dainty configuration are not to be noted in any ground squirrel or chickaree.

To distinguish, in the field, the differences between the five kinds recorded for the park is quite another matter. This requires some study and an appreciation for finer distinctions. Their ranges include the territory from the western boundary to the highest peaks, but, with one exception, they do not overlap.

The Tahoe chipmunk is found in the areas occupied by three other kinds. This is probably because it has a much greater tendency to take refuge in trees and hunt food in bushes. Consequently, it does not seriously compete with the others, which are largely ground dwellers.

For some reason, all chipmunks are scarce in Yosemite Valley, but they may easily be seen in the Mariposa Grove of Giant Sequoias, or near Glacier Point, as well as in the high country.

There is one species in Yosemite National Park that may be rather easily identified. The alpine chipmunk is very small, less than eight inches over-all, and quite pale in coloration. It extends its range into the rocky shoulders of our highest mountains. I have seen it at least 13,000 feet in elevation, very near the summit of Mt. Lyell, scampering among the polemoniums.

Our chipmunks are mainly seed eaters, utilizing the membranous cheek pouches for transporting their harvest. Their slender forefeet are better suited for handling and shelling small seeds than for digging, so extensive burrows in the ground are seldom made.

They prefer shelter obtained by tunneling in soft, decayed wood, or seek it among crevices in the rock. Apparently some of our chipmunks hibernate and others do not, but available information regarding their winter habits is very incomplete.

Captive Sierra flying squirrel, eating apple.

Photo by Joe Grater

Captive Sierra flying squirrel, eating apple.

Flying squirrel landing on tree trunk.

Sequoia Natl. Park Photo

Flying squirrel landing on tree trunk.

The Sierra flying squirrel, while quite common, is not likely to be seen by many Yosemite visitors. It is abroad only at night, spending the daylight hours curled up, with its tail over its face, in an old woodpecker hole or rotten snag. In winter, while skating at Camp Curry rink, I have seen these little gliders, zipping like tiny shadows across the lighted area as they leaped from the tall trees along the side of the rink. In summer, Valley campers find that their bacon and butter have been nibbled during the night by “some creature larger than a mouse.”

Probably the most adept of the squirrels at traveling through the branches from tree to tree, it has the added ability to volplane across openings between trees where the branches are not close enough to be spanned by a simple jump. These glides are as near flying as the squirrel ever achieves. It leaps from a height, extends the web of furred skin that connects wrists and ankles, straightens out the flat tail and glides downward at an angle, sometimes covering as much as 150 feet at a single glide and usually landing near the base of the trunk of another tree. It has the power to change course while in flight, and can check its speed for landing by manipulation of the web and tail. Always it must have a height from which to start. It cannot fly by its own power, as does the bat.

The trail camper in the coniferous forest belt is most likely to encounter flying squirrels, especially if he sleeps without a tent and keeps a flashlight handy. If the bed is near a large tree, possibly a shower of bark will rattle down when a flying squirrel starts racing up the trunk after completing a jump. Perhaps the disturbance created as one (or more) of them investigates the larder will awaken the sleeper so he can use his flashlight for observation. “Bob” McIntyre, now of Mt. Rainier National Park, once had a whole family of flying squirrels try to get the trout from the creel hanging above his sleeping bag while he was camped in the Ten Lakes Basin.* [* See Yosemite Nature Notes, (27)9: 113, September 1948. See also (29)4 36-41, April 1950, for an interesting account of a captive Sierra flying squirrel.]

FLYING SQUIRREL

From “Mammals of Lake Tahoe” by Robert T. Orr, California Academy of Sciences.

FLYING SQUIRREL

Seen at close range, the Sierra flying squirrel is a lovely creature. The fur, brownish-gray above, whitish below, is soft, silky, dense and warm. The flat tail looks more like a large feather from a bird. Besides serving as a “balance rod” as in the case of the other tree squirrels, it is believed to be used as a rudder during “flights.” The eye, large, dark and lustrous, is a beauteous thing. It is believed that the large size of the eye assists the flying squirrel to see better at night.

The diet includes more meat than is generally true of squirrels. Insects are taken, bird nests sometimes robbed, and other flesh relished when obtainable. The usual squirrel foods such as nuts, fruits, berries, fungi, seeds and buds are eaten. It is these that are stored by Sierra flying squirrels against the season of scarcity, for they are active the year around.

POCKET GOPHER

From Kodachrome by M. V. Hood

POCKET GOPHER

Pocket gophers, of which three kinds are found in the park, spend most of their lives underground. Yosemite forms are from light to dark brown in color, with head and body some six inches long, plus a tail of about the proportions of a match stick, bare at the end. With this bare tip the gopher can feel any obstruction that may be in the way when he needs to back up in a tunnel. The “pockets” are fur-lined pouches in the cheeks. The prominent chisel-teeth always show; the lips do not cover them. The gopher is able to close its lips behind them and thus keep the dirt out of its mouth when it uses the teeth to aid in digging.

The gopher has a heavy head and broad face, not pointed and streamlined as in the mole. The gopher’s eyes and ears are small but they are easily visible and much larger than those of the mole. The forefeet of the gopher are equipped with strong digging claws but are not modified into “paddles” as in the mole. The gopher’s fur is short and smooth, but not plush-like (reversible) as in the mole.

There may be confusion as to the identity of the workings of the two. When mole runways are just at the surface, the earth is always cracked. In winter, pocket gophers tunnel in the snow and pack some of these with earth from the deeper burrows so that a solid core is formed. When the snow melts, these “cores” are lowered to the surface of the ground and remain like giant “earthworms.” These are often mistaken for the work of the mole. The mole builds a symmetrical mound of earth from below by pushing it up through the hole, never leaving it open or showing himself in the process (p. 58). The gopher pushes the earth up to the hole, then dumps it outside so that a lopsided hill is built. He finally plugs up the entrance.

Pencil indicates cheek pouch of pocket gopher.

From Kodachrome by Anderson

Pencil indicates cheek pouch of pocket gopher.

Forefoot of pocket gopher is fine for digging.

From Kodachrome by Anderson

Forefoot of pocket gopher is fine for digging.

Pocket gopher hole showing eccentric dirt pile.

Photo by Author

Pocket gopher hole showing eccentric dirt pile.

Pocket gopher mound. Note that it is lopsided.

Photo by Author

Pocket gopher mound. Note that it is lopsided.

Pocket gophers make long series of tunnels about half a foot below the surface, with dirt piles thrown up at different spots above them. These are mainly exploratory tunnels, thrown out in search of food which consists of almost any vegetable material, roots, stems and all. Occasionally a side vent will be put up to the surface so the animal may forage near by, but never far from the safety of his subway. Often a lower level of tunnels contains nesting and storage chambers.

“Cores” of winter pocket gopher runs.

From Kodachrome by Anderson

“Cores” of winter pocket gopher runs.

In wilderness country like Yosemite National Park, pocket gophers have long played an important part in the development of the soil. They bring up a very respectable amount of earth from below —in one area, 1.64 pounds per square yard, according to Grinnell and Storer. Thus the weathering of the subsoil is hastened by its being deposited on the surface. The extensive tunnels permit aeration and the introduction of water to hasten the weathering of more subsoil. These tunnels also, in time of rains or melting snow, take up water, retard the run-off and conserve water.

Pocket gophers are prone to store far more greenstuff underground than they eat. The result is that more humus is mixed with the soil. The population of pocket gophers and other burrowing animals in Yosemite appears heavy enough so that the above factors are of real consequence in the development of soils under natural conditions and are a contribution to the well-being of the natural wild vegetation.

The Allen pocket mouse was added to the park list on July 9, 1950, by Ranger O. L. Wallis. He found a specimen that had been killed by a car one-half mile above South Entrance on the road to the Mariposa Grove.

This subspecies is about 8 1/2 inches long. More than half this length is tail. The upper parts are a shiny, grizzled, brownish tan, with spiny hairs on the hips. The feet and underparts, including the underside of the tail, are white. Along the sides, between upper and lower parts, is a streak of beautiful, reddish tan. It has external cheek pockets, hence its name.

Golden beaver. Photographed immediately after release in Los Padres National Forest.

Courtesy Calif. Division of Fish and Game.

Golden beaver. Photographed immediately after release in Los Padres National Forest.

The golden beaver attains a length of nearly four feet and a weight of around forty pounds. The overall color is a golden brown, although this may not be readily apparent when the animal is seen at twilight, the fur wet from swimming.

A cautious observer may watch beavers at work in early evening or morning. The hours of greatest activity are from dusk to dawn. The loud splash of the flat tail, which may throw considerable water in the air when a beaver sounds the alarm, is a thrilling experience to see and hear.

Beaver dam on Big Creek. Height of dam ranges from 5-7 feet.

Photo by Anderson

Beaver dam on Big Creek. Height of dam ranges from 5-7 feet.

The tail is also used for a rudder when swimming, or a prop when sitting up, and may assist by pushing when the animal is in full flight on land. However, there is no evidence to indicate that it is ever used as a trowel, despite traditional accounts to the contrary.

Beaver tree on Big Creek.

Photo by Anderson

Beaver tree on Big Creek.

So far as the records show, this was never a species native to the park. At any rate, we know that our present colonies are the result of introductions made by the California Division of Fish and Game at sites very near our southern boundary. Properly, golden beavers are denizens of the lower drainages of the Sacramento and San Joaquin Valleys, at elevations of not more than 1,000 feet.

Hind footprint of golden beaver. Six-inch pencil.

From cast by M. V. Hood

Hind footprint of golden beaver. Six-inch pencil.

In 1944, the above-mentioned agency made two “plants” of golden beaver in Big Creek, near Fish Camp. Dams and other signs of activity may be seen from the road just below South Entrance, and have been noted well inside the park boundary. Another site of activity is in the stream by the golf course along the Wawona Road.* [* See Yosemite Nature Notes (27) 4:69-74, April 1948 and (30) 1.5-9, January 1951, for interesting accounts of beavers.]


The long-tailed, or California harvest mouse has been recorded in Yosemite but once, in 1936, near Cascades. It is very common at lower elevations outside the park, in grassy or shrubby situations. This form is easily mistaken for the common house mouse, but the tail is not nearly so scaly and the dark color of the upper surface of the tail is clearly differentiated from the dull white of the under surface. Further, the upper incisors of harvest mice have deep longitudinal grooves which are absent in the house mouse.

Gambel white-footed mouse.

Photo by R. G. Beidleman

Gambel white-footed mouse.

White-footed mice are probably the commonest type of mammal to be found in Yosemite National Park. They live in all suitable habitats from the lowest elevations on the western boundary up to at least 10,800 feet. The adults are quite striking, with brownish-tan upperparts, bright fawn flanks, white feet and underparts and large lustrous eyes. The fact that they keep themselves well-groomed enhances their clean and attractive appearance. They do not warrant the traditional aversion generated by the term “mice.”

The young are marked much like the adults, but the upperparts are a bluish gray. In “adolescence” the color resembles that of adults, but is paler in tone. These variations, due to differences in age, often confuse the uninitiated into believing that they represent different species.

Gilbert white-footed mouse. Note big ears.

From Kodachrome by Turner

Gilbert white-footed mouse. Note big ears.

Actually, three kinds of white-footed mice are known from Yosemite, but identification of a single individual would be extremely difficult without technical knowledge or the comparative material available in a museum study collection, having the specimen in hand. A possible exception is the Gilbert white-footed mouse. It is found only at the lower elevations of the park and has comparatively huge ears, three-fourths of an inch long. Records are rare in the park for this subspecies.

Rather than the well-known house mouse, it is usually some form of this group that enters the haunts of man in Yosemite. Sometimes it is in search of food that whitefoots come into the house. However, many times they seem not to bother the larder, but rather seek to find shelter and to store food brought in from the outside.

In the autumn of a “good acorn year” in Yosemite Valley, residents may hear these mice drop acorns while in the space above the ceiling. The rolling nut resounds, comparatively, as though it were a billiard ball. These seem tiny creatures to lug acorns so far above the ground level, but they accomplish it, oftentimes making the cache in a spot such as the toe of a coot hanging upside down, where it would appear impossible for them to climb while carrying such a load. In addition to acorns, their natural food consists mainly of dried seeds, fruits, nuts and insects. The chief period of activity is at night.

Nesting places near the caches in buildings are not spurned. Overshoes, hats, dresser drawers, upholstery (even in cars) and, of course, the spaces between walls or under rafters are among spots chosen for a cozy home made of shredded paper, cotton, kapok or similar materials, fluffed up by the teeth and nails. Aside from these artificial situations, the nest may be made in brush, hollow stumps, under the ground, beneath rocks, in fact almost any sheltered spot, depending on the habitat of the species. The softest of materials available, such as grass and milkweed silk, will be used. The winter nest must be especially warm, for they do not hibernate.

Young white-footed mouse. Probably Gambel.

Photo by R. G. Beidleman

Young white-footed mouse. Probably Gambel.

Certain studies in the Sierra indicate that there may be from five to ten whitefoots per acre. They are undeniably prolific, breeding when from five to eight weeks old, and having up to four litters a year. In such numbers, being mainly seed eaters, they must have an important impact on the plant life of the area. Natural checks, such as disease and seasons of poor food supply, have prevented them from becoming a plague here. As food for other interesting animals, from shrews to mountain lion, they make a significant contribution to the wildlife picture in the park.

The patient observer of white-footed mice in his camp or home may encounter two interesting types of behavior— “drumming” and “singing.” The drumming is done by the rapid vibration of the forefoot or forefeet. It can easily be heard if the mouse is among dry leaves, or on a piece of paper, so that the sound is amplified. The singing is so high-pitched that not all ears may catch the sound. I have never heard it, but it has been described as being something like the trill of a bird, though much weaker; or, again, as a shrill buzzing. Certainly the white-footed mice will bear acquaintance, beautiful, attractive little animals that they are.

Two kinds of wood rats are in our area, both of which are found at one time or another in Yosemite Valley. Westerners may be accustomed to referring to these animals as pack rats, trade rats or miner’s rats, varying with the locality. It is true that wood rats seem interested in collecting strange objects, and adding them to their nests. Sometimes other things may be brought back in place of those taken, but there is no evidence that this was done to replace them on an exchange basis. Nevertheless, many an interesting experience has arisen through the collecting habits of wood rats, especially the bushy-tail of the higher elevations.

Superficially, wood rats resemble the species of Old World rats which infest the haunts of man in “civilized” areas. Our native rats, however, keep themselves cleaner and present a more attractive appearance—soft fur, white feet and underparts, large, lucent eyes, and tail fully clothed with hair.

The Streator wood rat is grizzled brown above, with the short, brown hairs on the top of the tail contrasting with its white under surface. It ranges from the lowest elevations on the western boundary up to the level of Yosemite Valley, where it meets the range of the bushy-tailed wood rat. In the lower country this form makes conspicuous nests, on the ground or in trees. It may assemble nesting material in the crevices between the boulders of the talus slopes. These nests are constructed of almost anything that is available, but sticks play a large part in their makeup.

Bushy-tailed wood rat.

Bushy-tailed wood rat.

The bushy-tailed wood rat ranges from the Valley up to our highest mountain. It is larger than the other form, sandy tan above, with a flat, brush-like tail. The latter character is not so pronounced in the young. Rock slides at or above timberline are one locale for this species, where it nests back among the stones. It is reputed that the bushy-tail has a more highly developed “collecting instinct” than does the Streator.

Yosemite wood rats are chiefly nocturnal. Usually one is not aware of their presence unless attention is forcibly brought to them, as in a building or when they are the cause of some untoward event in the trailside camp. Their food consists mainly of vegetation — leaves, fruits, seeds, nuts, roots, bark, fungi and the like.

The Sierra lemming mouse is quite similar in appearance to the meadow mice (see illustration of latter), but has much softer fur, a shorter tail, and is sandy gray in color. It is sparsely distributed in the Sierra and not too much is known about its habits.

It is known generally as an inhabitant of the high meadows near patches of heather. However, a companion and I once captured one for the Yosemite Museum on a nearly barren ledge, two-thirds the way up Ragged Peak. On two occasions in the fall of 1949, I was present when Naturalist Robert N. McIntyre saw what must have been this species on the shoulder’s of Mt. Lyell, well above any meadows or heather. These were startled where weathered cracks in the granite supported a limited growth of grass and sedge in otherwise barren country. On both occasions the animal sought shelter under some rocks near at hand.

MEADOW MOUSE

From “Mammals of Lake Tahoe” by Robert T. Orr, California Academy of Sciences.

MEADOW MOUSE

Among the commonest of wild mammals in North America are the meadow mice, often called “field mice” by the farmer. The species in our area are chunky, short-tailed, with ears nearly hidden in the dark brown, dense, fluffy fur. The eyes are placed to afford a wide range of vision, particularly overhead. This must be very useful, since vigilance is the price of life. No predator scorns the meadow mouse as an item of food.

Tough little animals, they can endure severe extremes in living conditions. The fur is water resistant and they can even live where the runways are more than half submerged. They are found from the lowest level of the park nearly up to timberline.

Mouse runs in parted grass, Yosemite Valley.

Photo by Author

Mouse runs in parted grass, Yosemite Valley.

These are the path-cutters. Part the lush grass in the drier portions of the meadows, and a maze of runways will usually be revealed. The covered passageways reduce detection of the mice from above by predators. A system of underground tunnels may also be employed and, if the site is dry, the nesting chamber placed below ground. Often, the nest is made in a clump of grass or sedge, above the water level. Many other creatures, such as shrews and weasels, find the runs convenient highways and use them frequently.

Activity is carried on through all seasons. In winter, tunnels are made in the snow and nests are often built beneath the surface, which insulates them from the colder ground below. In 1942, an individual was seen traveling on the surface of the snow, then 32 inches deep, near the Rangers’ Club.

Meadow mice are among the most fecund of mammals. They start breeding when less than two months old and produce several broods, of half a dozen each, a year.

Green food, grass in the main, is preferred. Vegetable matter may provide 99 per cent of the diet. These prolific little creatures are part of the common currency which provides the carnivores with energy—energy which the grass gets from the sun, which the mouse gets from the grass, and which flesh-eaters cannot get in sufficient quantities directly from the plants because they are flesh eaters.

Three kinds have been recorded in the park, but they will be undistinguishable to the layman. Two are found in meadows and grasslands, not far from water. The Sierra meadow mouse is freer running, often using the ground under bushes and in thicket s. Generally, it makes no runways, though poorly defined paths may be found. Unlike the others, which are active any time, this form is not abroad so much in the daytime.

At the time of the Grinnell and Storer survey (1914-20), the house mouse was found about barns and dwellings in Yosemite Valley. The Yosemite Museum has a specimen of the Alexandrine or roof rat, taken in the valley in 1936. At this writing, I am unable to determine that Old World rats and mice, such as infest more “civilized” areas, are present in the park to a conspicuous degree. Mention has already been made of the differences between certain native forms and these species that were introduced from the Old World (see pp. 75-77).

Allen jumping mouse.

From Kodachrome by M. V. Hood

Allen jumping mouse.

An Allen jumping mouse is a pretty thing. The bright tan sides and pure white underparts, contrasting strongly with the reddish dark brown area on the head and back, give a clean, attractive appearance. The long hind legs indicate the source of the bounding gait responsible for the name. The exceptionally long tail serves as a “balance rod” to the animal when it makes leaps.

Jumping mice inhabit the cool, wet meadows and stream banks in the middle elevations of the park. They swim readily. Being generally nocturnal, they are seen usually only by accident. Unlike most mice, they hibernate.

The food consists of seeds, mainly those of grasses, though stems and leaves enter into their diet also.

Yellow-haired porcupine.

Yellow-haired porcupine.

There is a fair chance of seeing the yellow-haired porcupine anywhere in Yosemite from the lowest reaches up to timberline. If you find one, there is no need for apprehension, provided you keep out of reach. The “porky” is not aggressive. Porcupines cannot shoot their quills. The black, barbed outer tips of the yellow quills fasten themselves very easily into an “enemy” on contact or may be driven in firmly by the action of the thick, muscular tail.

“Stickers” are not the only body covering. They replace part of the underfur, but may be kept so flat as not to show through the overhairs, except on the tail, unless the animal is excited or on the defensive. The fur is brownish black, with a coat cf yellow-tipped guard hairs. The underparts lack quills.

Some predators take advantage of this last fact and manage to kill porcupines by flipping them over and attacking the under side. There are, however, plenty of cases on record where coyotes, wildcats and others have been seen with a “faceful.” The young possess hair and some spines at birth.

While the yellow-haired porcupine is particularly fond of the inner bark of trees, it feeds on other types of vegetation, including fruits. In winter, an individual may climb up a tree and remain there for days without coming down, dining on bark or buds when necessary. Much has been made of the damage to trees by porcupines, but, here in Yosemite, they do not seriously affect the scenic values of the forest. They do, however, give the Park Engineer a headache with their gnawing of the boards in certain structures, such as pit privies!

Remains of porcupine eaten by coyote.

Photo by W. B. Clum

Remains of porcupine eaten by coyote.

Tracks of yellow-haired porcupine. Hind food on left, front on right. Six-inch pencil.

From cast by M. V. Hood

Tracks of yellow-haired porcupine. Hind food
on left, front on right. Six-inch pencil.



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