Chapter II: Part 2

_Specimens examined._--Total, 7, distributed as follows: Los
Angeles County: 6 mi. E and 1 mi. S Llano, 3500 ft., 4; Mescal
Canyon, 4800 ft., 3.

=Sylvilagus audubonii sanctidiegi= (Miller)

Audubon Cottontail

Cottontails are common in the coastal sage scrub association and in and around citrus groves, but generally penetrate the mountains no farther than the lower limit of the chaparral association. They are everywhere on coastal alluvial slopes, except in the barren washes, and prefer patches of prickly-pear and often are loathe to leave its protection. After completely destroying a large patch of prickly-pear in the course of examining a wood rat house in the center of the cactus, I found hiding, in the main nest chamber of the house, a cottontail that dashed from its hiding place only when poked forceably with the handle of a hoe.

Cottontails are seldom above the sage belt in the chaparral associations, although along firebreaks and roads they occasionally occur there. Habitually cottontails escape predators in partly open terrain offering retreats such as low, thick brush, rock piles, and cactus patches; but on open ground beneath dense chaparral, cottontails may be vulnerable to predation.

Examinations of feces and stomach contents of the coyote reveals that it preys more heavily on cottontails than on any other wild species. Remains of several cottontails eaten by raptors were found in the sage belt.

In April, 1951, many young cottontails were found dead on roads in the sage belt, and a newly born cottontail was in the stomach of a coyote trapped four miles north of Claremont, on February 7, 1952.

_Specimens examined._--Total, 3, distributed as follows: Los
Angeles County: mouth of San Antonio Canyon, 2000 ft., 1 (PC).
San Bernardino County: 2 mi. NW Upland, 1600 ft., 2 (PC).

=Sylvilagus audubonii arizonae= (J. A. Allen)

Audubon Cottontail

This subspecies was recorded on the interior slope from 5200 feet elevation, as at the head of Grandview Canyon, down into the desert, and was common in the sagebrush flats of the upper pinyon-juniper association. Piles of feces under thick oak and mountain-mahogany chaparral indicated that the rabbits often sought shelter there. Adequate cover is a requirement for this rabbit on the desert slope of the San Gabriels; in the juniper and Joshua tree belts the species occurs in washes where there is fairly heavy brush, and only occasionally elsewhere. In the foothills, when frightened from cover in one small wash cottontails often run up over an adjacent low ridge and seek cover in the brush of the next wash. In the wash below Graham Canyon tracks and observations showed that cottontails were taking refuge in deserted burrows of kit foxes.

In the pinyon-juniper association cottontails and jack rabbits probably occur in roughly equal numbers, but in the Joshua tree belt cottontails seem far less numerous than jack rabbits. In the course of a two hour hike in lower Mescal Wash, at about 3500 feet, eleven jack rabbits and two cottontails were noted.

_Specimens examined._--Total, 2, distributed as follows: Los
Angeles County: 6 mi. E and 1 mi. S Llano, 3500 ft., 1; Mescal
Canyon, 4800 ft., 1.

=Sylvilagus bachmani cinerascens= (J. A. Allen)

Brush Rabbit

Brush rabbits inhabit the Pacific slope of the mountains from about 1200 feet in the coastal sagebrush belt up to at least 4500 feet in the chaparral, and are the only lagomorphs found commonly above the lower edge of the chaparral association. Here they were often on steep slopes beneath extensive and nearly impenetrable tracts of chaparral.

The ecologic niche of the brush rabbit is in brush where the plants form continuous thickets with little open ground. In the coastal sagebrush flats, areas supporting only scattered bushes are uninhabited by brush rabbits, while areas grown to extensive tracts of brush harbor them. When the brush rabbit's mode of escape from its enemies is considered, the reason for their habitat preference becomes more clear. Almost invariably these rabbits seek escape by running through the densest portions of the brush, never appearing in the open; in this way they travel quickly away from the source of danger without being observed. Because they avoid being seen in the open, and do not seek safety largely through running ability, they need continuous stretches of brush for escape. While hunting in the coastal sagebrush belt I have repeatedly seen frightened brush rabbits turn and dart beneath the bushes a few feet from a human being rather than be driven into the open.

A great horned owl shot in March, 1951, in the sage belt, had in its stomach the remains of a freshly killed adult brush rabbit. Although coyotes and brush rabbits often occur in the same general sections of the sage flats, remains of these rabbits have been notably scarce in coyote feces from these areas. This is probably because the coyote hunts along clearings and in open brushland, precisely the type of habitat avoided by brush rabbits.

Family SCIURIDAE

=Sciurus griseus anthonyi= Mearns

Western Gray Squirrel

Gray squirrels were on both slopes of the San Gabriels in oak woodland. A gray squirrel was observed in April of 1948, as it climbed a telephone pole adjacent to an orange grove near Cucamonga. This, and one noted bounding up a slope of greasewood chaparral near Cattle Canyon, were the only gray squirrels seen in areas which were not grown to oaks or adjacent to oak woodland. In the lower foothills gray squirrels were invariably found in association with valley oak, this plant forming limited woodland areas in canyon bottoms. In the upper chaparral association the squirrels frequented the large scrub oaks growing on talus slopes and canyon sides. In the yellow pine woodland, gray squirrels are restricted to black oaks, often where they formed mixed stands with the conifers. On the interior slope these squirrels were found only at the lower edge of the yellow pine woodland where black oaks are common. There, in the vicinity of Big Pines, they were present between roughly 5800 and 7000 feet, while on the Pacific slope they inhabited oak woodland from 1600 feet to about 7000 feet elevation.

In Live Oak Canyon in December of 1950, tracks indicated that a bobcat had killed a gray squirrel in a small draw beneath the oaks. In Evey Canyon on March 6, 1951, while watching for bats at late twilight, I observed a gray squirrel traveling through the branches of a nearby oak. A great horned owl glided into the oak in an attempt to catch the squirrel, which leaped quickly into a dense mass of foliage and escaped. For roughly ten minutes the owl perched in the oak watching its intended prey, then flew off down the canyon amid frantic scolding by the squirrel.

On March 17, 1951, a female gray squirrel taken at about 3500 feet elevation in San Antonio Canyon contained two embryos, each roughly 40 millimeters long.

=Spermophilus beecheyi beecheyi= (Richardson)

Beechey Ground Squirrel

From the coastal sage belt, into the yellow pine forest of the Pacific slope, this species is common on land cleared by man or disturbed in the course of construction, or on severely eroded slopes where the original climax vegetation is partly or completely absent. Thus in the sage belt, ground squirrels live along dirt roads through the brush, on the heavily eroded banks often found in the foothills, on land grazed closely by sheep, and in those parts of major washes such as San Antonio and Cucamonga washes where scatterings of huge boulders offer prominent vantage points. In San Antonio Canyon _Spermophilus_ was restricted to the vicinity of roads and firebreaks, and an especially large colony of at least forty individuals lived at a dump one mile southwest of Camp Baldy at about 4500 feet elevation. Ground squirrels used burned stems of large laurel sumac as observation posts. Because of a preference for open areas offering unobstructed outlooks, ground squirrels originally probably did not penetrate the main belt of heavy chaparral on the Pacific slope of the range except in some of the large washes.

In the spring of 1951 and the preceding summer there was a marked increase in the ground squirrel population near Padua Hills as a result of sheep grazing on approximately one-half square mile of sage land. Grasses and smaller shrubs were eaten down to the ground, and in some places coastal sagebrush and _Haplopappus_ were killed by browsing and trampling. The area formerly had a sparse growth of bushes with intervening growths of tall grasses and one colony of perhaps 20 ground squirrels; but after the sheep grazing the area was open brushland with large clear spaces on which the herbage was trimmed to the ground, and had at least four colonies of ground squirrels as large as the first. Also there were other ground squirrels established in various parts of the area. Probably the dry weather in the winter of 1950-51 with consequent retardation of the vegetation aided the spread of the squirrels in this area.

In the sage belt, most ground squirrels are dormant by December. In 1951, after a mild winter, squirrels were noted on January 25 near Padua Hills. On February 8, 1951, males in breeding condition were collected, and on March 16, a female taken near San Antonio Wash carried three small embryos. In early March of 1951, ground squirrels were active at 4500 feet elevation in San Antonio Canyon.

_Specimen examined._--Los Angeles County: 1 mi. S and 2 mi. E
Big Pines, 8000 ft., 1.

=Spermophilus beecheyi fisheri= (Merriam)

California Ground Squirrel

This ground squirrel inhabited the desert slope of the mountains up to 5000 feet elevation, and was most common in the juniper belt; burrows often were made under large junipers. In May, 1949, ground squirrels were common in the rocks adjacent to Mescal Wash at an elevation of 4500 feet. In an apple orchard near Valyermo, squirrels fed on the fallen fruit in early November of 1951.

No squirrel was seen in December, January, and February, indicating that all were below ground in winter.

_Specimen examined._--San Bernardino County: Desert Springs,
4000 ft., 1 (PC).

=Ammospermophilus leucurus leucurus= (Merriam)

Antelope Ground Squirrel

Antelope ground squirrels were common in the Joshua tree woodland where they were noted up to 4500 feet elevation in Graham Canyon. None was found on the pinyon slopes, possibly because of the competition offered there by _Eutamias merriami_, or because the rocky nature of the soil there rendered burrowing difficult.

Although observed less often in winter than in summer, this species is active all year. On February 6, 1949, in Mescal Wash, an antelope ground squirrel was foraging over the snow which was at least six inches deep. These squirrels were attracted to the carcasses of rodents used as bait for carnivore sets, and caused a good deal of trouble by disturbing the traps.

Antelope ground squirrels used the topmost twigs of box-thorn bushes extensively as lookout posts, and many of their burrows were at the bases of these thorny bushes. This habit of regularly using observation posts is well developed in each species of ground squirrel found in the San Gabriels.

_Specimens examined._--Los Angeles County: 6 mi. E and 1 mi. S
Llano, 3500 ft., 2.

=Eutamias speciosus speciosus= (Merriam)

Lodgepole Chipmunk

This chipmunk was characteristic of the most boreal parts of the San Gabriel Mountains. It was recorded from 6800 feet elevation at Big Pines, to an altitude of approximately 9800 feet near Mt. San Antonio, and was common where coniferous timber was interspersed with snowbrush chaparral. In upper Icehouse Canyon and near Telegraph Peak these chipmunks were associated with lodgepole pines and chinquapin, and one mile east of Mt. San Antonio individuals were often observed in thickets of manzanita. This chipmunk usually shunned pure stands of coniferous timber except as temporary forage ground.

On Blue Ridge these chipmunks used the uppermost stems of snowbrush as vantage points, and when disturbed ran nimbly over thorny surfaces of the brush in seeking refuge in the tangled growth.

In early November of 1951, these animals were not yet in hibernation on Blue Ridge. They were noted on November 6, after the season's first snows had melted; on November 13, however, a cold wind with drifting fog kept most of them under cover, and only two were noted in the course of the day.

_Specimen examined._--Los Angeles County: 1 mi. S and 2 mi. E
Big Pines, 8100 ft., 1.

=Eutamias merriami merriami= (J. A. Allen)

Merriam Chipmunk

The lower limit of the range of this species, on the coastal face of the range, is roughly coincident with that of manzanita--that is to say, it begins in the main belt of chaparral above the lower foothills. _E. merriami_ seems to reach maximum abundance amid the granite talus, and scrub oak and _Pseudotsuga_ growth at the upper edge of the chaparral association. It was absent, however, from all but the lower fringe of the yellow pine forest association.

On the desert slope _merriami_ was partial to rocky areas in the pinyon-juniper association but was also in the black oak woods on the Ball Flat fire road near Jackson Lake. Nowhere was _Eutamias merriami_ and _E. speciosus_ observed on common ground.

_Specimens examined._--Los Angeles County: San Antonio Canyon,
5500 ft., 2 (1 PC).

=Glaucomys sabrinus californicus= (Rhoads)

Northern Flying Squirrel

No specimens of this species were taken in the field work in the San Gabriels, nor did I find any rangers or residents of the mountains who had seen flying squirrels in the area. Nevertheless sign found in the white fir forests in the Big Pines area indicated that flying squirrels may occur there. On a number of occasions dissected pine cones were noted on the horizontal limbs and bent trunks of white firs. These cones were too large to have been carried there by chipmunks, and gray squirrels were often completely absent from the areas. I suspect that extensive trapping in the coniferous forests of the higher parts of the mountains would produce specimens of flying squirrels. Willett (1944:19) mentions that flying squirrels probably occur in the San Gabriel Mountains.

Family GEOMYIDAE

=Thomomys bottae pallescens= Rhoads

Valley Pocket Gopher

This gopher was found below about 5000 feet elevation in disturbed or open areas from Cajon Wash at Devore westward all along the coastal base of the San Gabriel Range. In the lower part of the chaparral belt the gopher evidently was absent from the chaparral-covered slopes, but was common along roads and on fire trails.

Burt (1932) and von Bloeker (1932) discuss the distribution of the three subspecies of this species, _pallescens_, _neglecta_, and _mohavensis_, which are in the San Gabriel Mountains area, and Burt indicates that _pallescens_ grades toward _mohavensis_ in the southern part of Antelope Valley.

=Thomomys bottae neglectus= Bailey

Valley Pocket Gopher

In the forests of yellow pine and white fir of the higher parts of the San Gabriel Mountains the workings of this gopher were common, and sign of its presence was found above 4500 feet on both slopes of the mountain range. The rocky character of the coastal slope seems to limit the occurrence of gophers, for they are not continuously distributed there. On the desert slope they occur locally down into the pinyon-juniper belt.

In the vicinity of Big Pines, on the interior slope, these gophers preferred broken forest where snow brush or other brush occurred; their workings, however, were also found beneath groves of conifers and black oaks. The abundance of earth cores resting on the duff indicated that this species is active in the snow in winter.

_Specimens examined._--Total, 5, distributed as follows: Los
Angeles County: 2 mi. E Valyermo, 4600 ft., 2; 3 mi. W Big
Pines, 6000 ft., 1; 1 mi. S and 2 mi. E Big Pines, 8000 ft., 2.

=Thomomys bottae mohavensis= Grinnell

Valley Pocket Gopher

One specimen of this subspecies was taken on December 31, 1951, in the Joshua tree belt, eight miles east of Llano, 3700 feet elevation.

Family HETEROMYIDAE

=Perognathus fallax fallax= Merriam

San Diego Pocket Mouse

This pocket mouse is restricted to the coastal sage scrub association, and was recorded from Cajon Wash west to Live Oak Canyon. The mouse does not inhabit even the lower edge of the chaparral belt, but in the coastal sage flats is usually the most abundant rodent. In disturbed parts of the coastal sage belt _fallax_ is less common, and was never trapped in channels of rocky washes. Trap lines in the eroded adobe banks of the foothills, where white sage and coastal sagebrush are the dominant plants, took mostly these pocket mice. Although the soil of such slopes is compact and seemingly is unsuitable for burrowing by heteromyids, _fallax_ is the most common rodent. Because few burrows of pocket mice were noted there, it is possible that the many old unused burrows of _Spermophilus_ and _Dipodomys_ which honeycomb certain parts of adobe banks are used also by _fallax_; some of these burrows shelter _Peromyscus eremicus_ and _Peromyscus californicus_.

These mice are inactive above ground in cold weather. In the sage belt near Thompson Canyon, where this subspecies had been found to be the most common rodent, none was trapped on the sub-freezing night of December 3, 1948, although other rodents were found in usual numbers. Individuals have been taken on nights of intermittent rain, yet none has been trapped on freezing nights.

This species is characteristically heavily infested by a large species of mite. Usually these mites congregate around the base of the tail.

On October 11, 1949, one lactating female and two carrying embryos were taken.

_Specimens examined._--Total, 11, distributed as follows: Los
Angeles County: 4 mi. N and 1 mi. E Claremont, 1900 ft., 5; 3
mi. N Claremont, 1600 ft., 6 (5 PC).

=Perognathus fallax pallidus= Mearns

San Diego Pocket Mouse

On the desert slope of the mountains this species is found in the part of the pinyon-juniper association that is between elevations of 4000 and 5200 feet. The mouse is absent from the higher chaparral and pinyon-covered slopes, but is present on south slopes in the pinyon belt where more open growths of pinyons and scrub oaks are interspersed with yucca. I recorded this pocket mouse from the vicinity of Cajon Pass west to Valyermo.

The local distribution of _pallidus_ is striking because of its close positive correlation with the distribution of yucca. On benches around 5000 feet, where yuccas are scattered in their occurrence, _pallidus_ is nearly always taken near (often right at the base of) this plant. Lower in the juniper belt the dry rocky south slopes supporting yucca plants are well populated by _pallidus_, while adjacent flats, and north slopes grown to antelope brush and scrub oak, are completely uninhabited. Near the mouth of Grandview Canyon, on steep rocky southern exposures grown sparsely to burro weed and yucca, one hundred traps produced in one night eight _pallidus_ and no other rodents. Here many of these pocket mice were trapped on large fractured rock outcroppings, where most or all of the mice probably lived in the daytime in the deep cracks; in any event no burrows were noted near these rocks.

This species prefers barren slopes supporting yucca plants. These plants produce large seeds which are staple food items for _P. f. pallidus_ and other rodents during the lean part of the year, that is to say, late summer and autumn. Many of the dry capsules of the yucca plants were examined in October, 1951, and these generally still contained a few seeds. Pocket mice taken in October usually carried in their cheek pouches seeds of yucca together with some other material, and often they carried only the seeds of yucca. Probably the wind shakes only a few seeds out of the capsules at a time, thus tending to drop the seeds over a fairly long period.

Trapping in winter in the juniper belt revealed that these pocket mice were not active above ground on nights colder than about 40 deg. F. On nights when the temperature was about 36 deg. F. none was taken, but on the one night in late December, 1948, when the minimum was 44 deg. F., several specimens were taken. In this same area in May 1949, pocket mice were the most numerous rodents. Because of their evident sensitivity to cold weather, these mice must remain below ground for weeks at a time during the cold weather of December and January.

Specimens of _pallidus_ from the desert slope of the San Gabriels are grayer (less brown) than specimens taken farther southeast in the Mojave and Colorado deserts. Further sampling of populations of _Perognathus fallax_ from areas adjacent to the San Gabriels might demonstrate differences of sufficient magnitude to warrant subspecific distinction of the San Gabriel population. Possibly, however, the San Gabriel series manifests only local variation in the race _pallidus_. Grinnell (1933:54) characterizes the ecological niche of the race _pallidus_ as being "open, sandy ground, often ... surrounded by rocky slopes," whereas these pocket mice in the San Gabriels inhabited gravelly or rocky juniper-dotted benches.

_Specimens examined._--Total, 11, distributed as follows: Los
Angeles County: 5 mi. E and 4 mi. S Llano, 4500 ft., 7; 2 mi. E
Valyermo, 4500 ft., 3; 4 mi. E Valyermo, 5000 ft., 1.

=Perognathus californicus dispar= Osgood

California Pocket Mouse

Mice of this subspecies were recorded from the lower chaparral association below about 4000 feet elevation along the coastal face of the San Gabriel Range. They were trapped on greasewood-covered slopes, in mixed growths of white sage and buckwheat, and beneath scrub oak and lilac chaparral; however none was taken in the heavy chaparral of the upper parts of the chaparral association.

One small juvenile in gray pelage was taken in San Antonio Canyon on October 1, 1951.

_Specimens examined._--Total, 5, distributed as follows: San
Bernardino County: Lytle Canyon, 4000 ft., 2 (PC). Los Angeles
County: San Antonio Canyon, 3000 ft., 3.

=Perognathus californicus bernardinus= Benson

California Pocket Mouse

On Blue Ridge these mice were recorded between 7100 and 8000 feet elevation. Here they were restricted to dense tracts of snowbrush and sagebrush, often where these tracts were interspersed with, or beneath, open groves of conifers. These mice seemed to favor areas where this thick brush was broken by patches of open, grass-covered ground. Benson (1930:450) records this subspecies from Swarthout Valley, near Big Pines, at 6860 feet elevation.

While setting traps for pocket gophers one mile southwest of Big Pines, in September of 1951, I frightened a pocket mouse from its burrow. The animal jumped into the tangle of interlacing twigs of a nearby clump of snowbrush, and with great dexterity climbed into the center of the bush, where it was lost to view. I was surprised at the facility with which this saltatorial rodent traveled through the network of small branches.

In winter, in areas inhabited by this mouse, snow covers the ground for long periods during which these mice are probably forced to remain below ground.

_Specimens examined._--Los Angeles County: 1 mi. S and 2 mi. W
Big Pines, 7400 ft., 2.

=Dipodomys panamintinus mohavensis= (Grinnell)

Panamint Kangaroo Rat

This rat is common in the Joshua tree and juniper belts, and locally penetrates the pinyon belt at about 5000 feet elevation. It occurs regularly along the entire desert slope of the San Gabriel Mountains.

The upper limit of the range of this species roughly coincides with the upper limit of the juniper belt, and within this range it was found to inhabit areas having widely different soil types. It occurred on the sandy ground of desert washes, the gravelly soil of the juniper-clad benches, and the mixed sandy and rocky ground of washes in canyons. A preference is shown by _panamintinus_ for fairly level ground. Rough terrain or steep slopes are generally avoided, whereas rather large colonies of these kangaroo rats are found in small flats of the desert foothills.

Below about 4500 elevation on the interior slope this species was the most numerous rodent, and seemed to reach maximum abundance in the Joshua tree association. About 500 trap-nights in the juniper belt near Graham Canyon yielded 31 specimens, whereas about 300 trap-nights in Joshua tree flats took 34 individuals.

The cheek pouches of many specimens taken in early winter contained green shoots of grass and little dry material. On many occasions rat traps set next to wood rat nests beneath large junipers produced _panamintinus_, and many of these animals had their cheek pouches crammed full of juniper berries.

In December, 1948, _panamintinus_ was trapped consistently on nights when the temperature dropped to below 20 deg. F. On December 27, 1948, after a three inch snowfall, tracks of this species were noted in the snow at the mouth of Mescal Canyon.

Parts of the skulls of this species were found in many coyote feces from the desert slope.

_Specimens examined._--Total, 11, distributed as follows: Los
Angeles County: Mescal Wash, 4000 ft., 8 (6 PC); 2 mi. E
Valyermo, 4600 ft., 3.

=Dipodomys merriami merriami= Mearns

Merriam Kangaroo Rat

This kangaroo rat barely enters the area under consideration and is almost restricted to the Joshua tree association, for only a few individuals were taken at the lower edge of the juniper benches. This species inhabits the Joshua tree belt all along the desert base of the San Gabriels.

As mentioned in the description of the Joshua tree association, the relative numbers of _Dipodomys merriami_ and _D. panamintinus_ shifted from 1948 to 1951, possibly concurrent with the seasons of low rainfall in this period. Whereas in 1948 _merriami_ was decidedly less abundant than _panamintinus_ in the Joshua tree belt, in 1951 the numbers were reversed.

In December, 1951, it was found by tending the traps in the early evening that _merriami_ foraged fairly early before the ground had frozen solidly.

_Specimens examined._--Los Angeles County: 2 mi. NW mouth of
Graham Canyon, 3500 ft., 5 (PC).

=Dipodomys merriami parvus= Rhoads

San Bernardino Kangaroo Rat

One specimen of this subspecies was trapped on November 26, 1951, in a sandy channel of Cajon Wash near Devore beneath a clump of scale-broom.

=Dipodomys agilis agilis= Gambel

Pacific Kangaroo Rat

This species was found below about 4000 feet elevation all along the coastal face of the range and reached maximum abundance in the level tracts of coastal sage. It was one of the most abundant rodents there, usually being second to _Perognathus fallax_ in point of numbers. Large colonies of kangaroo rats occurred locally on sandy ground adjacent to large washes. The rats were found sparingly on the foothill adobe banks and in the greasewood chaparral of the lower foothills, but in heavy chaparral where a layer of plant debris covered the ground, such as on north slopes grown to scrub oak and lilac, kangaroo rats were completely absent. Thus, in the lower chaparral belt, this rodent had a discontinuous distribution.

The coyote probably is one of the major predators of these kangaroo rats; remains of this rodent were often found in coyote feces, and coyotes excavated many burrow systems in large kangaroo rat colonies in the sandy ground near San Antonio Wash. The soil there is so soft that coyotes probably were often successful in digging out their prey. The shed skin of a large Pacific rattlesnake (_Crotalus viridis helleri_) was found four feet inside the mouth of a kangaroo rat burrow; probably this reptile preys on _agilis_. Great horned owls (_Bubo virginianus pacificus_) come down nightly from the chaparral to hunt in the sage flats. Beneath the perches of these owls I have found pellets containing bones of _agilis_.

_Specimens examined._--Total, 13, distributed as follows: Los
Angeles County: San Antonio Wash, 1900 ft., 11 (10 PC); 4 mi. NE
Claremont, 1600 ft., 2.

=Dipodomys agilis perplexus= (Merriam)

Pacific Kangaroo Rat

All the specimens of this species from the desert slope of the San Gabriel Range are referred to the subspecies _perplexus_. They were taken in brushy habitats between the elevations of 4500 and 7400 feet. Throughout much of this area _perplexus_ was found only in certain restricted areas more or less surrounded by inhospitable ground. For example, at 7400 feet on Blue Ridge, they were found occasionally in the strips of sagebrush and lilac brush which locally capped this ridge. Often these patches of chaparral on Blue Ridge were surrounded by areas unsuitable for kangaroo rats: on the Pacific slope, talus, oaks, and yellow pines prevailed; on the ridge scattered yellow pine groves were present; and on the steep desert slope there were yellow pines and white firs. In Swarthout Valley _perplexus_ was found in flats that supported basin sagebrush and _Haploppus_, while the coniferous forests to the south, and pinyon-covered slopes to the north were uninhabited. On flats supporting antelope brush and juniper, _perplexus_ was often common, but it did not penetrate the chaparral of adjacent slopes grown to scrub oak and mountain-mahogany. In general then, _perplexus_ was found in fairly open brushy flats or slopes, even where these were surrounded by unsuitable habitats.

Specimens of _D. agilis_ from the desert slope two miles east of Valyermo are referrable to the subspecies _perplexus_. A series taken in Cajon Wash at Devore, on the Pacific slope, is intermediate between _agilis_, of the coastal slope of the San Gabriels, and _perplexus_ of the desert slope, but approaches more nearly the later subspecies. Thus, different subspecies of _D. agilis_ occur on opposite slopes of the San Gabriel Mountains, with intergradation taking place in the Cajon Pass area and probably also at the west end of the Mountains.

Both scrub oak acorns and juniper berries were found in the cheek pouches of this subspecies, and one immature individual taken in Swarthout Valley had its cheek pouches stuffed with approximately 550 seeds of brome grass.

On November 13, 1951, at 7500 feet on Blue Ridge, a small juvenile was taken; it must have been born not earlier than September.

_Specimens examined._--Total, 17, distributed as follows: Los
Angeles County: 2 mi. E Valyermo, 4600 ft., 3; 5 mi. E Valyermo,
1; 1 mi. E Big Pines, 6600 ft., 6; 1 mi. S and 2 mi. W Big
Pines, 7400 ft., 2. San Bernardino County: Cajon Wash, 1/2 mi.
SW Devore, 2200 ft., 5.

Family CRICETIDAE

=Reithrodontomys megalotis longicaudus= (Baird)

Western Harvest Mouse

This species inhabited grassy areas of the coastal sage belt, and reached maximum abundance on cleared land grown thickly to weeds and scattered brush. The mouse was only locally abundant--being scarce throughout much of the sage belt--but was found under contrasting conditions. In San Antonio Wash the species was taken among rocks and sparse weeds, at Palmer Canyon specimens were trapped on a barren ridge sparsely clothed with greasewood and white sage, and also one mile E of Big Pines in flats supporting basin sagebrush and a fairly dense growth of grasses. The western harvest mouse was recorded from 1500 feet elevation to 3200 feet on the Pacific slope, and at 6600 feet near Big Pines on the desert slope.

Those specimens of harvest mice from near Big Pines may be grading toward the desert race _megalotis_; my series of specimens from this locality, however, is too small for clear indications on this point.

Individuals in juvenal pelage were taken on November 26, 1951, near Devore.

_Specimens examined._--Total, 6, distributed as follows: Los
Angeles County: 1 mi. E Big Pines, 6600 ft., 2; Palmer Canyon,
2000 ft., 1; 4 mi. N Claremont, 1700 ft., 3 (PC).

=Peromyscus eremicus eremicus= (Baird)

Cactus Mouse

In Mescal Wash on the desert slope of the San Gabriels, this mouse was one of the most abundant mammals and was the only rodent other than _Peromyscus maniculatus_ regularly trapped in the barren channels of washes. In Mescal Wash, at an altitude of 4000 feet, _eremicus_ occurred along with the chaparral-inhabiting _Peromyscus boylii_ and _Peromyscus californicus_. The two species last mentioned were associated with the occasional large patches of manzanita, antelope brush, and other brush of the wash, whereas _eremicus_ was trapped in the rocky and sandy channels among scattered bushes of scale-broom. No specimens of _eremicus_ were taken on the juniper-clad benches adjacent to the wash.

_Specimens examined._--Los Angeles County: Mescal Wash, 4000
ft., 10 (4 PC).

=Peromyscus eremicus fraterculus= (Miller)

Cactus Mouse

This mouse was recorded from 1900 feet elevation, one mile south of the mouth of San Antonio Canyon, to 3200 feet elevation in Cajon Canyon. This subspecies is characteristic of the sage belt and shows a strong preference for the rough rocky areas found in dry washes. Although in many areas the channels of the washes are immediately adjacent to sandy sagebrush-covered flats, _eremicus_ is not common in the latter areas. Rocks seem to be essential to _eremicus_, for sandy areas in the sageland which were devoid of rocks yielded only an occasional specimen. For example, 100 trap-nights in the main channel of San Antonio Wash yielded 23 _eremicus_ and only six other rodents; while in the sandy sage areas nearby 200 trap-nights yielded only one _eremicus_ and 32 other rodents.

In lower San Antonio Canyon _eremicus_ seemed restricted to the rocky canyon bottom, none having been trapped on the steep slopes nearby. This subspecies occurs commonly, however, on the adobe banks grown to white sage at the base of the foothills. There _eremicus_ occurred on common ground with _Perognathus fallax fallax_, and was often the only _Peromyscus_ taken.

This species may be restricted by temperature; washes above 4000 feet elevation, which seemed suitable were uninhabited by these mice.

On December 1, 1949, two females taken at the mouth of Palmer Canyon had well advanced embryos. A female trapped in San Antonio Canyon on September 19, 1951, was lactating. Juveniles were caught in the sage belt in October, 1951.

_Specimens examined._--Total, 6, distributed as follows: Los
Angeles County: San Antonio Canyon, 2500 ft., 1; San Antonio
Wash, 1800 ft., 5 (PC).

=Peromyscus californicus insignis= Rhoads

California Mouse

This mouse inhabits areas supporting chaparral on the coastal slope of the San Gabriels below 5000 feet. In the chaparral it is usually the most plentiful rodent, being dominant on slopes which have been burned over and on which greasewood chaparral has taken over. On one such slope at the head of Cow Canyon, at 4500 feet, this was the only rodent trapped, although an occasional wood rat house was noted. Trapping records gave the impression that this form was the most ubiquitous rodent in the entire chaparral belt. Nearly every trap line, even in such non-productive areas as oak woodland, took the California mouse; and in many areas, as in thick lilac brush, this mouse was by far the most abundant rodent. Specimens were taken on the damp ground next to San Antonio Creek, and in the riparian growth. In San Antonio Wash the California mouse was found in thickets of laurel sumac and lemonade berry, or other large shrubs, but were absent from most of the adjacent sageland. The one place where they were found away from heavy brush was on a series of barren adobe banks, near Palmer Canyon, clothed mostly with white sage. Here they found shelter in the unused burrows of kangaroo rats and ground squirrels.

The only place on the desert slope where this species was taken was in Mescal Wash. There it was taken occasionally near the large clumps of antelope-brush and manzanita which grew in the main channels of the wash.

Lactating females of this species were taken in October, 1949, and February, 1950. Two pregnant females were trapped on February 25, 1950, at the mouth of Palmer Canyon.

_Specimens examined._--Total 16, distributed as follows: Los
Angeles County: Mescal Wash (4200 ft., 4; 4300 ft., 1; 4500 ft.,
1), 6(2IM); San Antonio Canyon, 4500 ft., 1; San Antonio Canyon,
3000 ft., 5; mouth of Palmer Canyon, 1900 ft., 4 (PC).

=Peromyscus maniculatus gambeli= (Baird)

Deer Mouse

This species occurs from 1000 feet elevation to above 9000 feet elevation on the Pacific slope of the Mountains, but although probably the most widespread rodent in the area it is absent from many habitats. This mouse reaches maximum abundance in the coastal sage scrub association, particularly where the soil is sandy with scattered vegetation--usually coastal sagebrush and black sage. On the foothill adobe slopes none was trapped, nor have any been taken in most of the chaparral habitats. A few _gambeli_ were trapped amid the talus beneath growths of scrub oak and bay trees in San Antonio Canyon, at 4300 feet elevation. On Blue Ridge, at elevations of from 7200 feet to 8300 feet, this mouse inhabited areas clothed with snowbush, basin sagebrush, currant, and scattered conifers, and was found sparingly in the coniferous forests. Thus this species lives on contrasting soil types in association with many different vegetational assemblages, from the coastal base to the crest of the range.

There is a rather wide variation in color in _gambeli_ from the San Gabriels. Certain individuals taken in open, sandy coastal sage areas are pale, some being indistinguishable from examples of _sonoriensis_ taken in the pinyon-juniper association on the desert slope. Specimens from San Antonio Canyon have somewhat darker pelage than those from the sage belt, and than individuals taken on Blue Ridge. Possibly a large series of _Peromyscus maniculatus_ from the San Gabriel Mountains would show definite local trends in color of pelage.

This species is active on sub-freezing and rainy nights as evidenced by trapping results, and at Big Pines there were tracks around the bases of conifers after a heavy snowfall in December, 1951. Several females taken in the sage belt in October, 1948, carried embryos, and a lactating female was recorded from Blue Ridge on November 13, 1951. Juveniles have been taken in September, October, November, and December.

_Specimens examined._--Total, 9, distributed as follows: Los
Angeles County: 1 mi. S and 2 mi. W Big Pines, 7400 ft., 3; 1
mi. S and 2 mi. E Big Pines, 8200 ft., 1; 4 mi. NE Claremont,
1900 ft., 2; San Antonio Wash, 1800 ft., 3 (PC).

=Peromyscus maniculatus sonoriensis= (Le Conte)

Deer Mouse

This subspecies is associated with contrasting types of soil and vegetation. It is seemingly absent from the upper pinyon-juniper sage flats and areas grown to chaparral, but is fairly common on the gravelly benches dotted with junipers, and in the washes issuing from the canyons on the desert slope. It is present in small numbers in the Joshua tree association.

In 1951 the numbers of _sonoriensis_ were noticeably less than in 1948; probably this was correlated with the series of dry winters in this period. In December, 1948, this animal was one of the most common rodents in Mescal Wash, 200 trap-nights yielding thirteen specimens; but in November, 1951, none was taken. In parts of the juniper belt, where an average of about six _sonoriensis_ was taken per 100 trap-nights in 1948, the average had dropped to one per 100 trap-nights in 1951.

Specimens of this species from the desert slope of the mountains have been assigned to the subspecies _sonoriensis_. Those from Blue Ridge tend toward _sonoriensis_ in color, and may be considered as intergrades between this subspecies and _gambeli_.

This species was active on nights when the temperature was as low as 10 deg. F., and individuals were trapped in the juniper belt in December, 1948, when four inches of snow lay on the ground.

Gray-pelaged juveniles were taken on the desert slope in December, 1948, and a female taken in Mescal Canyon on December 22 of this year carried four embryos near term.

_Specimens examined._--Total, 11, distributed as follows: Los
Angeles County: 8 mi. E and 4 mi. S Llano, 4000 ft., 6 (4 PC);
Mescal Canyon, 4800 ft., 5.

=Peromyscus boylii rowleyi= (J. A. Allen)

Brush Mouse

The main range of this mouse in the San Gabriel Mountains lies between 1600 and 6000 feet elevation on the Pacific slope of the Mountains, thus encompassing much of the chaparral and oak woodland associations. It was the most common mammal in the oak woodland association in the lower foothills and often was trapped there on leaf mold beneath the oaks. While trapping for shrews I regularly took this species in riparian growth right down to the edge of the water. In San Antonio Canyon many _boylii_ were trapped beneath logs and dense vegetation, and on wet seepage slopes adjacent to the creek.

This species shows a definite predilection for rocky habitats where these occur in the chaparral. In heavy lilac brush near Camp Baldy _Peromyscus boylii_ was outnumbered by _P. californicus_, yet where talus slopes or boulder piles occurred _boylii_ was more numerous. At the head of Cow Canyon amid boulders beneath scrub oak, bay, and big cone-spruce, this species was especially abundant and no other _Peromyscus_ was taken.

Of special interest is the occurrence of this mouse on the desert slope of the mountains; there it was taken beneath scrub oaks in the pinyon-juniper association at the mouth of Mescal Canyon, and amid boulder and debris piles in Mescal Wash at 4000 feet elevation. While manzanita and scrub oak grew in the wash at the points of capture, the animals were actually surrounded by the desert conditions of the Joshua woodland, and associated with such desert forms as _Onychomys torridus pulcher_ and _Peromyscus eremicus eremicus_.

Immature individuals were taken in October, November, February, and March, and a female with two large embryos was taken near Icehouse Canyon on November 8, 1951.

_Specimens examined._--Total, 8, distributed as follows: Los
Angeles County: Mescal Wash, 4000 ft., 1; Mescal Canyon, 4800
ft., 2; San Antonio Canyon, 5200 ft., 2; San Antonio Canyon,
4500 ft., 1; San Antonio Canyon, 2800 ft., 1; Thompson Canyon,
1800 ft., 1 (PC).

=Peromyscus truei montipinoris= Elliot

Pinon Mouse

Only once was this mouse found outside the pinyon-juniper association of the desert slope; in November, 1949, several were collected near Cajon in mixed manzanita, scrub oak, and greasewood chaparral. This was the only _Peromyscus_ of regular occurrence in the pinyon-juniper area, and was recorded from the upper limit of this association, near Jackson Lake, at 6000 feet, to the lower limit of the association at the mouth of Graham Canyon at roughly 4000 feet elevation.

Although in the juniper belt _truei_ often occurs on common ground with _Peromyscus maniculatus sonoriensis_, the habitat preferences of these animals are generally complementary. Where the mice occur together, traps set in a variety of locations caught _Peromyscus maniculatus_, but typically traps set amid the brush or on the open ground away from the junipers were productive. On the contrary _truei_ was invariably trapped quite near the junipers and often in association with the large nests of _Neotoma fuscipes simplex_. In fact traps set right on the beds of litter beneath the junipers were most likely to catch _truei_. Records kept of trapping localities show that _truei_ was without exception trapped within twenty feet of some treelike shelter such as junipers, pinyons, Joshua tree or scrub oaks. Thus _Peromyscus maniculatus_ occupies the open stretches between the trees, while _truei_ inhabits the ground beneath and immediately adjacent to the trees. In Nevada the pinon mouse prefers rocky areas (Hall, 1946:520). In the San Gabriel Mountains this mouse does not seem to have this predilection.

In the juniper belt _truei_ was second to _Dipodomys panamintinus_ in point of numbers. In the course of 500 trap-nights in the juniper belt twenty-two _truei_ were taken with thirty-six _Dipodomys_.

I consider my series of _Peromyscus truei_ from the desert slope of the San Gabriels to represent the subspecies _montipinoris_. The series is closely comparable to specimens of the subspecies _montipinoris_ in the California Museum of Vertebrate Zoology from the Mount Pinos area, but differs from specimens of the race _chlorus_ from the San Bernardino Mountains in certain diagnostic characteristics. In his recent paper on _Peromyscus truei_, Hoffmeister (1951) considered the populations of this species in the San Gabriels to be of the race _chlorus_. Hoffmeister had only one specimen available from the San Gabriel Mountains (Lytle Creek, on the Pacific slope) which was intermediate between _montipinoris_ and _chlorus_, but on the basis of cranial measurements it was referred to the race _chlorus_. Specimens of _Peromyscus truei_ from the eastern end of the desert slope of the San Gabriel Mountains and the Cajon Pass area would probably demonstrate that the race _montipinoris_, which occupies the desert slope of the San Gabriels, intergrades with the race _chlorus_, which occurs in the San Bernardino Range immediately to the east, in the Cajon Pass area. Although _montipinoris_ occurs on the desert slope of the San Gabriels, _chlorus_ may occur on the Pacific slope. I took no specimens of the pinon mouse on the Pacific slope of the San Gabriel Mountains.

In December, 1948, many small juveniles were taken in the juniper belt, and on October 15, 1951, two females trapped at the head of Grandview Canyon had embryos: one three and the other four. On November 13, 1951, a partially gray-pelaged subadult female was trapped which had recently suckled young.

_Specimens examined._--Total, 17, all in Illinois Museum of
Natural History, distributed as follows: Los Angeles County:
Mescal Canyon, 4500 ft., 8 mi. SE Llano, 11; Mescal Canyon, 4300
ft., 2; 6 mi. SE Valyermo, 5100 ft., 1; Grandview Canyon, 6 mi.
SE Valyermo, 5100 ft., 1. San Bernardino County: 1 mi. W Cajon,
3200 ft., 2.

=Onychomys torridus pulcher= Elliot

Southern Grasshopper Mouse

Grasshopper mice seemed to be partial to the more sandy parts of the Joshua tree flats where the mice were trapped regularly but not abundantly. This mouse inhabited the barren sandy channels of Mescal Wash but was rare on the adjacent juniper-clad benches. In the arid, sandy washes this typical desert rodent penetrated the high pinyon-juniper association.

Wherever grasshopper mice occurred they were outnumbered by most of the other rodent species. For example, on November 26, 1949, below Graham Canyon, 100 snap traps yielded 10 _Dipodomys panamintinus mohavensis_, 2 _Dipodomys merriami merriami_, 4 _Peromyscus maniculatus sonoriensis_, and 3 _Onychomys torridus pulcher_.

Where abandoned kangaroo rat burrows were common in the Joshua tree belt these burrows were used as retreats by _Onychomys_. Some traps set at the entrances to old burrows caught grasshopper mice.

_Specimens examined._--Total, 7, distributed as follows: Los
Angeles County: 8 mi. E and 3 mi. S Llano, 3500 ft., 1; Mescal
Wash, 4200 ft., 5 (3 PC); 2 mi. S Valyermo, 4600 ft., 1 (PC).

=Neotoma lepida intermedia= Rhoads

Desert Woodrat

This species was on the Pacific face of the Mountains from 1600 feet elevation in the coastal sage belt, to 4800 feet elevation in open groves of big cone-spruce and scrub oak of the chaparral association.

The local distribution of this woodrat is determined by suitable nesting sites. Although taken in different types of vegetation, _lepida_, without exception, was associated with rocky areas or areas supporting patches of prickly-pear cactus. In the channels of San Antonio Wash, _lepida_ was commonly associated with jumbles of boulders and boulder-dotted cut banks. There the vegetation is sparse, and the rats dwell among the rocks; only their droppings and faint trails indicate their presence. Among boulders _lepida_ builds only small houses of sticks and debris, and even these only occasionally. The effect of the prickly-pear cactus on the distribution of _lepida_ in the sageland is striking; trap lines there yielded no woodrats where extensive rock piles and patches of prickly-pear were absent, but many rats were taken where patches of prickly-pear are plentiful. On an acre supporting coastal sagebrush at the mouth of San Antonio Canyon, at 1800 feet elevation, there were fourteen patches of prickly-pear, each covering at least thirty square feet. In these patches there were thirteen occupied woodrat nests. Only one patch lacked an occupied nest, and this one contained the remains of an old nest. On this acre there were at least thirteen individuals. In the sagebrush belt only an occasional large patch of cactus lacks a woodrat house occupied by _lepida_. Seemingly _Neotoma fuscipes_ does not build houses in patches of prickly-pear.

Most of the houses built by _Neotoma lepida_ are small and simple as compared to those of _Neotoma fuscipes_, and often in rocky areas no nests are in evidence. The most elaborate nests are built among the pads and spines of the prickly-pear and under laurel sumac or other large shrubs growing near washes. One of three houses examined at the mouth of San Antonio Canyon was on sandy ground in a patch of _Opuntia_ measuring approximately 11 x 14 feet. The house was 14 inches high and 41 x 37 inches at the base. It was built around the main stem of the prickly-pear and a rock about 10 inches in diameter. The house was constructed of sticks of coastal sagebrush and buckwheat, and was dotted with dissected fruits and flowers of the prickly-pear. The main chamber was arched over by the main stem of the prickly-pear and was roughly 12 x 19 inches, inside dimensions, being reached through two three-inch openings, one on the east side of the chamber and one on the north side of the chamber. Two cup-shaped nests were inside the chamber, these being constructed mostly of grasses, and each resembling a well constructed bird nest 4 inches in diameter. The grass nests were free of feces, but feces were piled up against the west side of the chamber with many snail shells and dissected fruits and flowers of prickly-pear. Thirty-five inches from the main chamber was a third grass nest on the ground beneath a cluster of cactus pads. Next to this there was a blind burrow about eight inches long, and one and three-quarters inches in diameter. No burrow led to the main chamber, in this or in either of the other houses, but all had at least one short blind burrow beneath the house.

At many houses there were one to three grass nests outside the house on the ground, within four feet of the house. From each nest a well worn path lead to the house. Traps set in these nests invariably caught woodrats.

The many prickly-pear fruits and snail shells in and around the houses of _lepida_ probably were remnants of food. So many of the rodents caught in traps near woodrat nests were partly eaten--usually the brains were taken--that I suspect the woodrats of eating their relatives. The heads of many composite annuals were piled near woodrat nests.

Immature individuals were taken in September, October, and early November, and on September 26, 1951, a lactating female was trapped near Palmer Canyon.

An old female bobcat trapped in Thompson Canyon had masses of cactus thorns beneath her skin, especially about the forelegs. These thorns were probably received while she was foraging in growths of prickly-pear for woodrats. The other bobcats from San Antonio Wash also had accumulations of thorns under the skin of the forelegs. Fragments of the skulls of _Neotoma lepida_ were recovered from horned owl pellets and coyote feces.

_Specimens examined._--Total, 7, distributed as follows: Los
Angeles County: San Antonio Canyon, 4500 ft., 2; San Antonio
Wash, 1800 ft., 5 (2 PC).

=Neotoma lepida lepida= Thomas

Desert Woodrat

These woodrats were present in rocky situations along the desert slope from the lower edge of the juniper belt down into the desert. Specimens were taken in piles of boulders in Mescal Wash, and amid rock outcroppings on the steep, barren, south slopes at the base of Grandview Canyon, whereas none was found on the juniper-clad benches.

This woodrat built no nests in rocky areas; however, in the Joshua tree belt _N. l. lepida_ often built small nests at the bases of large standing or prostrate Joshua trees. There sticks from creosote bushes, along with cow dung and small stones were favorite building materials. Judging from the large number of unused woodrat nests in the Joshua tree flats it seemed that this rat was formerly far more common than it was in the period of this study.

_Specimens examined._--Total, 9, distributed as follows: Los
Angeles County: 6 mi. E and 1 mi. S Llano, 3500 ft., 4; Mescal
Wash, 4200 ft., 5 (3PC).

=Neotoma fuscipes macrotis= Thomas

Dusky-footed Woodrat

This subspecies was widely distributed along the coastal slope of the mountains from the coastal sage belt, at roughly 1600 feet, up to 6500 feet at the lower edge of the yellow pine forest and was most common in the chaparral association.

In the coastal sage belt these woodrats are restricted to wash areas where large chaparral plants such as lemonadeberry and laurel sumac are used as nesting sites. In San Antonio Wash the occasional large juniper trees almost invariably harbor the nests of _fuscipes_. The general absence of suitable nesting sites in the sage belt probably limits the spread of _fuscipes_ in this area.

In the upper part of the chaparral belt in talus these woodrats live beneath the angular boulders and build no visible houses. Several areas of talus occupied by woodrats were examined carefully and no sign of houses was noted.

Two juveniles were found in the stomach of a rattlesnake (_Crotalus viridis helleri_) killed in May, 1948, at the mouth of Evey Canyon. Remains of woodrats were found in feces of the coyote and gray fox.

Lactating females of this species were taken on March 16, and October 2, 1951.

_Specimens examined._--Total, 4, distributed as follows: San
Bernardino County: Icehouse Canyon, 5500 ft., 2. Los Angeles
County: San Antonio Canyon, 2800 ft., 2.

=Neotoma fuscipes simplex= True

Dusky-footed Woodrat

These rats were recorded from the yellow pine forests on Blue Ridge, at 8100 feet, down to the lower edge of the juniper belt, at 3800 feet. Their presence there as elsewhere was determined by the occurrence of adequate cover. On Blue Ridge they were taken in and near patches of snowbrush, currant, and choke cherry, and one was taken beneath a pile of logs where no nest was in evidence.