Accounts of Species

Sagebrush Scrub Association

Major Plants

Bromus sp.Artemisia tridentataChrysothamnus nauseosusPurshia glandulosa

This association is found on only the crest and desert slope of the range between 5000 and 8000 feet elevation. There it characteristically occupies flats and clearings in the yellow pine forest and pinyon-juniper woodland. The dominant plant of the association is basin sagebrush, and in many places this plant forms mixed growths with snowbrush andHaplopappus. The low brush of this association is formed by closely spaced bushes with grasses growing between.

Because of its limited occurrence in the San Gabriel Mountains, this association there has relatively little effect on mammalian distribution. Locally, nevertheless, the presence of this association governs the distribution of certain mammals. For example, on Blue Ridge, islands of sagebrush amid the conifers provide suitable habitat forDipodomys agilis perplexusandPerognathus californicus bernardinus; and in Swarthout ValleyD. a. perplexus,Reithrodontomys megalotis longicaudus, andLepus californicus deserticolaare seemingly restricted to the sagebrush flats.

Joshua Tree Woodland Association

Major Plants

Yucca brevifoliaLycium AndersoniiEriogonum fasciculatumTetradymia spinosaEphedra sp.Larrea divaricata

This association is on the piedmont that dips toward the Mojave Desert from the interior base of the San Gabriels. The widely spaced Joshua trees with low bushes between, and the dry washes breaking the level terrain below the mouths of canyons are typical of this area. Field work was extended no farther down into the desert than about the 3500 foot level, where this association was still dominant.

Although the vegetation of this area is scattered and sparse, presenting a barren and sterile aspect, the area supports a rather high population of rodents. The soil at the bases of many large box-thorn- and creosote-bushes is perforated by burrow systems ofDipodomys panamintinusorDipodomys merriami, and those burrows abandoned by kangaroo rats are used as retreats byOnychomys torridusandPeromyscus maniculatus. The mammals of this association are all characteristic of the fauna of the Mojave Desert, with the ranges of such species as the coyote and jack rabbit extending well up the desert slope of the mountains.

The mammals listed below were taken in 1948 in roughly 400 trap nights in the Joshua belt, at an elevation of 3500 feet, one mile below the mouth of Graham Canyon.

Table 9.—Yield of 400 Trap-nights in the Joshua Tree Belt.

Populations ofDipodomys merriamiandD. panamintinusfluctuate widely, possibly in response to weather cycles. In November of 1948 trapping in the Joshua belt showed thatpanamintinusoutnumberedmerriamiapproximately three to one, whereas in December of 1951, after a succession of unusually dry years,merriamiwas the more numerous. Further,merriamioccurred in the lower parts of the juniper belt in 1951 where in 1948 it seemed to be absent.

Dipodomys merriami merriamiandOnychomys torridus pulcherare diagnostic of the Joshua tree woodland association in the San Gabriel Mountains area, since few individuals of either species occur outside of this association.

PLATE 1

Fig. 1.View of typical coastal sage scrub association, showing in foreground white sage, and coastal sagebrush. The adobe banks beyond are grown mainly to white sage. Small mammals are abundant in this association, withDipodomys agilis,Perognathus fallax, andSylvilagus auduboniibeing characteristic of the area. Photo March 25, 1952, at mouth of San Antonio Canyon, 1800 feet elevation.

Fig. 2.View of a main channel in San Antonio Wash on Pacific slope. The wash is a distinct habitat in the coastal sage scrub association, and is the preferred habitat ofPeromyscus eremicus fraterculusandNeotoma lepida intermedia. These rodents find shelter in the piles of boulders. Photo February 2, 1952, in San Antonio Wash, at 1700 feet elevation.

PLATE 2

Fig. 1.Southern oak woodland association. The open leaf-strewn floor of the woodland lacks shelter for ground-dwelling rodents and the population of rodents is small.Peromyscus boylii rowleyiis the commonest rodent. Photo March 10, 1952, in Evey Canyon, 2700 feet elevation.

Fig. 2.Yellow pine forest association, composed largely of yellow pines, white fir, and black oak. Photo April 27, 1952, at Big Pines, 6800 ft. elevation.

PLATE 3

Fig. 1.View of the sagebrush scrub association showing a nearly pure stand of basin sagebrush.Dipodomys agilis perplexusandReithrodontomys megalotis longicaudusoccur in this association, andPeromyscus truei montipinorisis present where this association merges with the pinyon-juniper association. Photo April 27, 1952, in Swarthout Valley, 6200 feet elevation.

Fig. 2.View of a pinyon pine woodland. This habitat constitutes the upper part of the pinyon-juniper association, and is the habitat ofNeotoma fuscipes simplex,Peromyscus truei montipinoris, andEutamias merriami merriami. Photo April 27, 1952, in Sheep Creek Canyon, 5500 feet elevation.

PLATE 4

Fig. 1.View of the juniper belt. This habitat forms the lower part of the pinyon-juniper association.Perognathus fallax pallidus,Dipodomys panamintinus mohavensis, andPeromyscus truei montipinorisare typical of this area. Photo April 27, 1952, at Desert Springs, 4300 feet elevation.

Fig. 2.Joshua tree woodland association. The characteristic mammals areDipodomys panamintinus mohavensis,D. merriami merriami, andOnychomys torridus pulcher. Photo January 4, 1952, 6 miles east and 2 miles south Llano, 3600 feet elevation.

Family DIDELPHIDAE

Didelphis marsupialis virginianaKerr

Virginia Opossum

The opossum is common in and near small towns and cultivated areas at the Pacific base of the mountain range and does not thrive away from human habitation; extensive trapping in the coastal sage and chaparral belts produced no specimens except immediately adjacent to citrus groves. Pequegnat (1951:47) mentions that opossums in the Santa Ana Mountains of southern California are in the lower parts of the larger canyons, especially near human habitation.

Specimens examined.—Los Angeles County: Claremont, 1600 ft., 2 (PC).

Family TALPIDAE

Scapanus latimanus occultusGrinnell and Swarth

California Mole

Workings of moles were found on the Pacific slope of the mountains from 1600 feet at Claremont up to 7500 feet on Blue Ridge, and on the Pacific slope beneath basin sagebrush in Cajon Canyon one mile from desert slope Joshua-tree flats, but not on the desert slope, although moles probably occur on that slope in some of the places where there is suitable habitat.

Near Camp Baldy in the sandy soil beneath groves of alders moles seemed to be especially abundant. Although common on the coastal face of the range, moles shunned compact, dry, or rocky soils. In the greasewood chaparral one-half mile west of the mouth of Palmer Canyon, where the soil was hard and rocky, mole tunnels were in soft soil that had accumulated at the edge of a fire road beneath a steep road cut. The assumption is that this accumulation contained insects attractive, as food, to the moles.

Specimens examined, 2: Los Angeles County: Camp Baldy, 4200 ft., 1(PC); Claremont, 1600 ft., 1(PC).

Family SORICIDAE

Sorex obscurus parvidensJackson

Dusky Shrew

Jackson (1928:124) recorded a specimen from Camp Baldy, 4200 feet, San Antonio Canyon.

Sorex ornatus ornatusMerriam

Ornate Shrew

Both of my specimens were taken amid riparian growth on the Pacific slope of the range.

Specimens examined, 2: Los Angeles County: San Antonio Canyon, 3500 ft., 1; Cobal Canyon, 5 mi. N Claremont, 1800 ft., 1 (PC).

Notiosorex crawfordi crawfordi(Coues)

Gray Shrew

One was taken in 1946 beneath a woodpile on the campus of Norton School, two miles northeast of Claremont, and examined by Dr. W. E. Pequegnat.

Family VESPERTILIONIDAE

Myotis yumanensis sociabilisH. W. Grinnell

Yuma Myotis

A female was taken in lower San Antonio Canyon, 2800 feet elevation, on September 27, 1951.

Myotis evotis evotis(J. A. Allen)

Long-eared Myotis

This species was observed and collected at several stations ranging from 2800 feet elevation in San Antonio Canyon, to Blue Ridge at 8200 feet, and down the desert slope to 6000 feet at Jackson Lake. This distribution encompasses most of the chaparral and yellow pine forest associations. Within these areas, however, this bat shows marked habitat preferences.

Woodland habitats seem to be preferred byevotis. At several ponds in lower San Antonio Canyon this bat was observed repeatedly as it foraged over the water and coursed low between rows of alders andBaccharis. At Blue Ridge in September, 1951, these bats foraged approximately six feet above the ground beneath the canopy of coniferous foliage and between the trunks of the trees.

Most of the bats were taken by stretching fine wires above the surface of a pond as outlined by Borell (1937:478). Collecting was generally carried on until at least 11:00 p. m., and the time at which each bat was taken at the pond was recorded, thereby making possible a rough estimate of the pre-midnight forage period of each bat commonly collected at the ponds. Usually bats taken at the start of their supposed forage period had empty or nearly empty stomachs, whereas those taken towards the end of their forage period had full or nearly full stomachs.M. evotisusually first appeared just at dark, well after the pipistrelles and California myotis had begun foraging. The forage period ofevotisseemed to begin approximately 30 minutes after sunset and to end approximately two and one-quarter hours later.

Individuals of this species were taken from May 4, to October 14, 1951. A female taken on May 19, 1951, in San Antonio Canyon, carried one minute embryo, and one taken in the same locality on June 8, had one embryo four millimeters in length.

Specimens examined.—Total, 12, distributed as follows: Los Angeles County: San Antonio Canyon, 2800 ft., 11; Claremont, 1100 ft., 1 (P.C.).

Myotis volans interiorMiller

Interior Long-legged Bat

Although seldom found to be plentiful, this bat was recorded from many points on both the coastal and desert slopes of the mountains. Specimens were taken in the chaparral association in San Antonio Canyon, near Jackson Lake among yellow pines, and in Mescal Canyon at the upper limit of the Joshua tree woodland. Bats, probablyvolans, were noted over sage flats at 8000 feet elevation on Blue Ridge. The only place where these bats appeared to be numerous was Jackson Lake on the interior slope; there, on September 19, 1951,volansappeared with the pipistrelles, and was the most common bat before dark.

An individual of this species taken on October 28, 1951, in a short mine-shaft in the pinyon belt at the head of Grandview Canyon was slow in its movements and felt as cold as the walls of the tunnel. It was late afternoon and the temperature outside the cave was below 40°F. The floor of the tunnel was covered with the hind wings of large moths of the genusCatocala;volansprobably hung in the cave while eating them.

The series ofvolansfrom the San Gabriels shows that the two color phases of this bat both occur in the area. Two specimens from Jackson Lake contrast sharply with the rest of the series in their dark coloration. Benson (1949:50) states that color variation in a series ofvolansfrom a given locality may be striking.

This bat was collected in San Antonio Canyon from 50 minutes after sundown to two hours and 40 minutes after sundown. In this area these bats did not visit the ponds in large numbers as they seemed to do on the desert slope.

A female taken on May 29, 1951, contained one embryo nearly at term.

Specimens examined.—Total, 9, distributed as follows: Los Angeles County: Mescal Canyon, 8 mi. E and 5 mi. S Llano, 4900 ft., 1; 3 mi. W Big Pines, Swarthout Valley, 6000 ft., 3; San Antonio Canyon, 2800 ft., 5.

Myotis californicus californicus(Audubon and Bachman)

California Myotis

On the Pacific face of the mountain range this bat was recorded commonly below approximately 5000 feet elevation, where it seemed to be most common in the oak woodland of canyons. On the desert slope it was collected at Jackson Lake in yellow pine woodland, in Mescal Canyon in the juniper belt, and bats presumably of thisspecies were observed at several points in the pinyon-juniper woodland.

Individuals of this species were often observed foraging from five to ten feet above the ground around the alders andBaccharisnear San Antonio Creek, but they did not fly so low or so near the vegetation as didMyotis evotis. Here they were taken from 18 minutes to 55 minutes after sunset; this indicates an early and short forage period.

This bat may be active even in winter. On February 8, 1952, in lower San Antonio Canyon, a bat, probably of this species, was noted foraging; and collecting in early November, 1951, yielded specimens.

On May 22, 1951, a female obtained in San Antonio Canyon had one five-millimeter embryo, and subsequently all the females examined had embryos until June 12, when collecting was discontinued.

Specimens examined.—Total, 16, distributed as follows: Los Angeles County: Mescal Canyon, 4800 ft., 2; Jackson Lake, 6000 ft., 1 (PC); San Antonio Canyon, 3900 ft., 1; San Antonio Canyon, 2800 ft., 12.

Pipistrellus hesperus merriami(Dobson)

Western Pipistrelle

This is the most obvious if not the most common bat of the lower coastal slopes of the San Gabriels. In the spring and fall of 1951 individuals were noted from 1700 feet in the coastal sage scrub association to the white fir forests on Blue Ridge at 8200 feet elevation and were commonest in the rocky canyons of the lower Pacific slope below 4000 feet, and usually foraged near the steep canyon sides high above the canyon bottoms.

Pipistrelles were generally the first bats to appear in the evening, although the times of their appearance were irregular. In April and May, in lower San Antonio Canyon, they appeared from 28 minutes before sunset to 30 minutes after sunset, with the average time of appearance eight and one-half minutes after sunset. LikeMyotis californicusthis pipistrelle seemed to have a short and early foraging period. No pipistrelles were recorded at ponds later than one hour and five minutes after sunset, and usually they were not seen later than 40 minutes after sunset. Most of the specimens taken later than one half hour after sunset had full stomachs. More than 50 pipistrelles were captured at the ponds in San Antonio Canyon; six were kept for specimens. This species is probably present in the area throughout the winter. Pipistrelles were activein early April in Evey Canyon, were observed in early November in San Antonio Canyon, and on January 26, 1952, an individual was noted foraging near the mouth of Palmer Canyon. They are probably not active in winter on the colder desert slope of the mountains.

Pipistrelles often foraged in loose flocks of about half a dozen individuals. On many occasions these groups were first seen foraging high up above the canyon bottom, then, as it grew darker, they descended and foraged within 50 or 100 feet of the floor of the canyon. Immediately before dark these groups seemed to have forage beats; one minute several pipistrelles would be overhead, and the next minute none would be in sight.

A female taken in San Antonio Canyon on June 8, 1951, contained two five-millimeter embryos.

Specimens examined.—Total, 6, distributed as follows: Los Angeles County: San Antonio Canyon, 2800 ft., 5; Evey Canyon, 2400 ft., 1.

Pipistrellus hesperus hesperus(H. Allen)

Western Pipistrelle

This species was common in the spring and autumn of 1951 from the lower edge of the yellow pine forest down into the belt of Joshua trees. In early April on the desert slope at 4800 feet in Mescal Canyon, pipistrelles foraged on evenings when it was windy but not cold. On cold evenings (when the temperature was below roughly 45°F) none was seen. On windy nights the pipistrelles often forsook their usual high forage habits and foraged 15 feet or so above the ground where the vegetation and outcrops of rock broke the force of the wind. In 1951 no pipistrelles were noted on the desert slope later than October 15.

Specimens examined.—Los Angeles County: Mescal Canyon, 4800 ft., 4.

Eptesicus fuscus bernardinusRhoads

Big Brown Bat

This bat was on the coastal slope from the sage scrub association at 1100 feet, up to 8000 feet on Blue Ridge, and on the desert slope down to the upper edge of the Joshua tree belt at 4800 feet in Mescal Canyon. It was the most common bat at the ponds in San Antonio Canyon in May and June of 1951, but in September and October of the same year none was obtained there.

On the Pacific slope of the San Gabriels the big brown bats segregate according to sex in the spring, the males occupying the foothills and mountains and the females the level valley floor at the coastalbase of the range. Of 70 big brown bats captured in May and June of 1951, at the ponds in San Antonio Canyon, only one was a female. A large colony of more than 200 individuals in a barn near Covina, in the citrus belt, was composed of only females.

Times of capture of this bat at the ponds in San Antonio Canyon ranged from ten minutes after sunset to two hours and thirty minutes after sunset. Generally these bats came to the ponds in groups of several individuals, and often more than a dozen were captured in the course of an evening's collecting.

Specimens examined.—Total, 7, distributed as follows: Los Angeles County: Mescal Canyon, 4800 ft., 1; San Antonio Canyon, 2800 ft., 2; Covina, 1100 ft., 4 (2PC).

Lasiurus borealis teleotis(H. Allen)

Red Bat

One female was taken on September 30, 1951, in San Antonio Canyon, at 2800 feet elevation. The descriptions which the citrus growers of the Claremont and Glendora vicinity give of the bats they find occasionally hanging in their citrus trees accurately describe this species. Its seasonal occurrence there is unknown.

Lasiurus cinereus cinereus(Pasilot de Beauvois)

Hoary Bat

Specimens were collected in spring in 1951 at elevations of 2800 and 3200 feet in San Antonio Canyon, on the coastal slope, and in Mescal Canyon at 4900 feet, on the desert slope. Large, fast flying bats, probably of this species, were seen at Jackson Lake, 6000 feet elevation, on October 15, 1951.

Hoary bats are present in the San Gabriels in the fall, winter, and spring. In 1951 the last spring specimen was taken on June 11, in Mescal Canyon; then collecting was discontinued until late September when the first hoary bat was taken on the thirtieth of that month. From this date on into the winter hoary bats were recorded regularly. They seemed to be as common in early June as in most of April and May; possibly some remain in the San Gabriels throughout the summer.

In spring these bats seem to segregate by sex; of twelve kept as specimens and at least an equal number captured and released only one was a female. All were captured above 2800 feet.

Hoary bats seem to have a long pre-midnight forage period, having been captured at ponds from 21 minutes after sunset, to three hours and 26 minutes after sunset. Generally those taken early had emptystomachs and those taken later had full stomachs. On the night of May 24, 1951, a hoary bat captured two hours and five minutes after sunset had only a partially full stomach.

On May 25, 1951, an unusual concentration of hoary bats was observed at a pond at about 3200 feet elevation, in San Antonio Canyon (Vaughan, 1953). The day had been clear and warm, one of the first summerlike days of spring. Beginning at 30 minutes after sundown hoary bats were collected until two hours and 35 minutes after sundown; in this period 22 were caught and at least as many more observed. Many were released after being examined, whereupon they hung on the foliage of nearby alders to rest and dry themselves. This concentration of hoary bats may have been due to a sudden beginning of migration with a resultant concentration of bats at certain altitudinal belts. The warm weather might have set off the migration. On evenings that followed subsequent hot days no such concentration of hoary bats was seen. B. P. Bole (Hall 1946:156) observed a concentration of hoary bats on August 28, 1932, in Esmeralda County, Nevada.

Several captiveMyotis californicusin a jar next to a pond in San Antonio Canyon set up a squeaking which seemed to attract a hoary bat. Repeatedly the large bat swooped over the jar.

Specimens examined.—Total, 12, distributed as follows: Los Angeles County: Mescal Canyon, 4900 ft., 2; San Antonio Canyon, 3200 ft., 2; San Antonio Canyon, 2800 ft., 8.

Antrozous pallidus pacificusMerriam

Pallid Bat

The pallid bat is probably the most common and characteristic bat of the citrus belt at the Pacific base of the mountains. Only once, on May 4, 1951, was this bat taken in the mountains. On that night two individuals were collected at 2800 feet in San Antonio Canyon. All of the other specimens and observations were from colonies in old barns and outbuildings in the citrus belt where these bats are found in spring, summer, and fall.

The impression gained by examining many mixed colonies ofAntrozousandTadaridawas that the former greatly outnumbered the latter. For example, a small colony of bats in an old barn near San Dimas Wash consisted of about thirty pallid bats and five freetails.

Large numbers of wings of moths of the familySphingidae, and legs and parts of the heads of Jerusalem crickets (Stenopelmatus fuscus)were beneath anAntrozousnight-roosting place in a barn near Upland.

Pallid bats were collected in 1951, from April 16 to October 17 but probably were active in the area into November.

Each of two pregnant females taken two miles northeast of San Dimas on April 20, 1951, carried two embryos 4 millimeters long.

Specimens examined.—Total, 6, distributed as follows: Los Angeles County: 2 mi. NE San Dimas, 1200 ft., 2 (1PC); Ontario, 1100 ft., 4 (3PC).

Family MOLOSSIDAE

Tadarida mexicana(Saussure)

Mexican Free-tailed Bat

This bat, regularly met with in the citrus belt at the coastal base of the range, occurred in small numbers with colonies ofAntrozous, and was once found with a colony ofEptesicusnear Covina. None of the females taken in April 1951 was pregnant.

Specimens examined.—Los Angeles County: 2 mi. NE San Dimas, 1200 ft., 4.

Eumops perotis californicus(Merriam)

Mastiff Bat

H. W. Grinnell (1918:373) mentioned individuals collected at Sierra Madre (at the coastal base of the San Gabriels west of the study area), and Sanborn (1932:351) reported specimens from Covina and Azusa. Probably this bat occurs locally all along the coastal base of the range.

Family LEPORIDAE

Lepus californicus bennettiiGray

California Jack Rabbit

This species was found in the coastal sage belt from Cajon Wash west to San Gabriel Canyon and was most plentiful in thin stands of sagebrush, and in and around citrus groves. Because of their preference for semi-open country, jack rabbits are absent from much of the coastal belt of sagebrush where the brush is fairly continuous, and they never were observed in the chaparral association.

Coyotes catch many jack rabbits and regularly forage around the foothill borders of the citrus groves for cottontails and jack rabbits.

A female examined on February 19, 1951, was pregnant, and one taken on March 15, 1951, carried three small embryos.

Specimens examined.—San Bernardino County: 2 mi. NW Upland, 1600 ft., 3 (PC).

Lepus californicus deserticolaMearns

California Jack Rabbit

There was sign of jack rabbits along the desert slope of the San Gabriels up to about 6700 feet, one-half mile west of Big Pines. They were fairly common in the Joshua tree belt, occurred less commonly in the juniper belt, and were present locally in small numbers in the pinyon-juniper association.

The population seemed to be at a low ebb from 1948 to 1952, when field work was done on the desert slope. I often hiked for an hour or more on the desert or juniper-covered benches without seeing a jack rabbit. The species was commoner in washes where as many as eleven were noted in two hours' hiking.

In December, 1951, below Graham Canyon, the leaves on large areas of many nearly recumbent Joshua trees had been gnawed down to their bases, and jack rabbit feces covered the ground next to these gnawings. Probably the Joshua tree is an emergency food used by the rabbits only when other food is scarce.

In years when the population of jack rabbits is not low they serve as a major food for coyotes. In the Joshua tree belt below Mescal Canyon, jack rabbit remains were fairly common in coyote feces, and tracks repeatedly showed where some coyote had pursued a jack rabbit for a short distance. A large male bobcat trapped in the juniper belt in Graham Canyon had deer hair and jack rabbit remains in its stomach.

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 openterrain 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 commonlyabove 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 anthonyiMearns

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 CanyonSpermophiluswas 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 Hillsas 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 andHaplopappuswere 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 byEutamias 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.

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