Chapter I: Part 1

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UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 7, No. 9, pp. 513-582, 4 pls., 1 fig. in text, 12 tables

November 15, 1954

Mammals of the San Gabriel Mountains of California

BY TERRY A. VAUGHAN

UNIVERSITY OF KANSAS LAWRENCE 1954

UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 7, No. 9, pp. 513-582, 4 pls., 1 fig. in text, 12 tables

November 15, 1954

Mammals of the San Gabriel Mountains of California

BY TERRY A. VAUGHAN

UNIVERSITY OF KANSAS LAWRENCE 1954

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Robert W. Wilson

Volume 7, No. 9, pp. 513-582, 4 pls., 1 fig. in text, 12 tables Published November 15, 1954

UNIVERSITY OF KANSAS LAWRENCE, KANSAS

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1954

25-5184

MAMMALS OF THE SAN GABRIEL MOUNTAINS OF CALIFORNIA

by

Terry A. Vaughan

CONTENTS

PAGE

INTRODUCTION 515

DESCRIPTION OF THE AREA 516

BIOTIC PROVINCES AND ECOLOGIC ASSOCIATIONS 518
Coastal Sage Scrub Association 521
Southern Oak Woodland Association 523
Chaparral Association 524
Yellow Pine Forest Association 526
Pinyon-juniper Woodland Association 527
Sagebrush Scrub Association 530
Joshua Tree Woodland Association 530

ACCOUNTS OF SPECIES 531

LITERATURE CITED 581

INTRODUCTION

This paper presents the results of a study of the mammals of the San Gabriel Mountains of southern California, and supplements the more extensive reports on the biota of the San Bernardino Mountains by Grinnell (1908), on the fauna of the San Jacinto Range by Grinnell and Swarth (1913), and on the biota of the Santa Ana Mountains by Pequegnat (1951).

The primary objectives of my study were to determine the present mammalian fauna of the San Gabriel Mountains, to ascertain the geographic and ecologic range of each species, and to determine the systematic status of the mammals. In addition, certain life history observations have been recorded.

Field work was done in the north-south cross section of the mountains from San Gabriel Canyon on the west, to Cajon Wash on the east; and from the gently sloping alluvium at the Pacific base of the mountains at roughly 1000 feet elevation on the south, over the crest of the range to the border of the Mojave Desert at an elevation of 3500 feet on the north. Camps were established at many points in the area with the object of collecting the mammals of each association and each habitat. Field work was begun in the San Gabriels in November 1948, and was carried on intermittently until March 1952. I was unable to carry on field work in any summer.

For advice and assistance in various ways I am grateful to Drs.
Willis E. Pequegnat, Walter P. Taylor, Henry S. Fitch, E.
Raymond Hall, Mr. Steven M. Jacobs and my wife, Hazel A.
Vaughan.

More than 350 mammals were prepared as study specimens; most of
these are in the University of Kansas Museum of Natural History.
Approximately a fifth of them are in the collection of the
Department of Zoology at Pomona College, and a few are in the
University of Illinois Museum of Natural History. No symbol is
used to designate specimens in the University of Kansas Museum
of Natural History. Specimens from the Department of Zoology of
Pomona College and the University of Illinois Museum of Natural
History are designated by PC and IM, respectively.

DESCRIPTION OF THE AREA

The San Gabriel Mountains are approximately sixty-six miles long, and average twenty miles wide. The main axis of the range trends nearly east and west, and extends from longitude 117 deg.25' to longitude 118 deg.30'. The widest part of the range is bounded by latitude 34 deg.7' and latitude 34 deg.30'.

The San Gabriel Mountains connect the Sierra Nevada with the Peninsular Ranges of southern California and Baja California. On the west the San Gabriels are bordered by the Tehachapi Mountains, which stretch northeastward to meet the southern Sierra Nevada; to the east, beyond Cajon Pass, the San Bernardino Mountains extend eastward and then curve southward to the broad San Gorgonio Pass, from which the San Jacinto Range stretches southeastward to merge with the Peninsular Ranges.

The rocks comprising the major part of the San Gabriel Mountains probably were intruded in Late Jurassic times, with severe metamorphic activity taking place concurrently. A long period of erosion followed after which deposition took place during much of the Tertiary. Deformation and uplift beginning in Middle Miocene times resulted in the formation of east-west-trending faults along both sides of the range. By repeated movements along these faults the Late Jurassic crystalline rocks were lifted above late Tertiary and Quaternary sediments and elevated above the surrounding terrain. Continued uplifts in post-Pleistocene time together with erosion in Recent times have shaped the San Gabriel Mountains (Oakeshott, 1937).

The alluvial slopes at the coastal base of the range give way to the foothills at roughly 1800 feet elevation; whereas the Mojave Desert merges with the interior foothills at elevations near 4000 feet. The crest or drainage-divide of the range varies from 6000 to 8000 feet in elevation, and many peaks are more than 8000 feet high. San Antonio Peak, the highest peak of the range, rises to an altitude of 10,080 feet. The mountains are characteristically steep and the slopes are deeply carved by canyons, the larger of which have permanent streams. The abruptness of the Pacific slope is in many places impressive. The horizontal distance from the top of Cucamonga Peak, at an elevation of 8911 feet, to the base of the coastal foothills directly to the south, at 2250 feet, an elevational difference of 6661 feet, is only 3.8 miles. From the base of Evey Canyon, at 2250 feet, to an unnamed peak to the northwest with an elevation of 5420 feet, the horizontal distance is 2.1 miles. Because of the steep, rocky nature of many of the slopes and the lack of soil on them, vegetation may be sparse even at high elevations. There are few meadows in the mountains.

Because the San Gabriels stand approximately thirty miles from the Pacific Ocean and are a partial barrier to Pacific air masses sweeping inland, the desert side and the coastal side of the range differ climatically. The coastal slope receives much heavier precipitation than the desert slope. The precipitation, for 1951, of 25.36 inches recorded at the mouth of San Antonio Canyon on the Pacific slope contrasts with 7.17 inches recorded at Valyermo at the desert base. Nearly all of the precipitation comes in winter. The higher parts of the range, above approximately 5000 feet, receive much of their mid-winter precipitation in the form of snow. Snow often extends down the desert slope well into the Joshua Tree belt. When there are heavy winter rains the channels of the usually dry washes are filled with rushing, turbid water. There are striking differences in temperature between the two sides of the range and between the lower elevations of the mountains and the higher parts. For example, in December 1951, the mean temperature at the base of San Antonio Canyon (2225 feet) at the coastal foot of the range was 55.4 deg.F, while at Llano (3764 feet) at the desert base it was 43.7 deg.F. In this same year the December mean for Table Mountain (7500 feet), on the desert slope, was 33.4 deg.F. The temperature means for July, 1951, at San Antonio Canyon, Llano, and Table Mountain, were 77.3 deg.F, 82.1 deg.F, and 69.2 deg.F respectively. The weather records for 1951 were used for illustration because average temperature and average precipitation for many other years are lacking for most of the weather stations in the area. There is an important difference in the humidity on the two sides of the range, but actual data are not available. At certain times, especially in spring, fog banks moving in from the Pacific Ocean frequently blanket the coastal base of the mountains and the foothills. On such days the fog generally "burns off" in the morning, but may persist into the afternoon or throughout the day. Never in my experience has fog spilled over the main part of the range far onto the desert slope, although the fog may push through the lower passes to be dissipated quickly in the dry desert atmosphere. The obvious differences in the biota on the two sides of the range are probably due to the contrasting climates.

BIOTIC PROVINCES AND ECOLOGIC ASSOCIATIONS

Because of the elevational extremes and attendant climatic contrasts in the San Gabriel Mountains, there is a rather wide range of environmental conditions. Four life-zones are represented: Lower Sonoran, Upper Sonoran, Transition, and Canadian. Within these zones certain ecologic communities can be recognized; these represent several biotic provinces. Table 1 shows the relationships between the environmental categories recognized by the writer in the San Gabriel Mountains. The biotic province and ecologic community system is that developed by Munz and Keck (1949), and the life-zone system is that of Merriam (1898).

TABLE 1.--RELATIONS OF THE MAJOR ENVIRONMENTAL CATEGORIES OF THE SAN GABRIEL MOUNTAINS.

======================================================================= Biotic province | Plant community | Life-zone | Slope ----------------+--------------------------+-----------------+--------- |1. Coastal sage scrub | Lower Sonoran | Pacific Californian |2. Southern oak woodland | Upper Sonoran | Pacific |3. Chaparral | Upper Sonoran | Pacific ----------------+--------------------------+-----------------+--------- Sierran |4. Yellow pine forest and | Transition | Pacific | limited areas of | Canadian | and | boreal flora | | Desert ----------------+--------------------------+-----------------+--------- Nevadan |5. Sagebrush scrub | Transition | Desert | | Upper Sonoran | ----------------+--------------------------+-----------------+--------- Southern Desert |6. Pinyon-juniper woodland| Upper Sonoran | Desert |7. Joshua tree woodland | Lower Sonoran | Desert ----------------+--------------------------+-----------------+---------

The Californian Biotic Province dominates the biotic aspect of the coastal slope of the range. Thirty-nine out of the seventy-two mammals recorded from the San Gabriels are typical of this Province. The coastal sage-flats at the Pacific base of the mountains and the vast tracts of chaparral of the coastal slope are included in this Province.

Forming a hiatus between the Pacific and the desert slope is the Sierran Biotic Province consisting of coniferous forests on the crest of the range. The chipmunk (_Eutamias speciosus speciosus_) and the introduced black bear (_Ursus americanus californiensis_) are the only two mammals which can be considered typical of this area. On the higher peaks of the range, such as Mount San Antonio and Mount Baden Powell, the Canadian Life-zone is represented by certain boreal plants.

At scattered points along the crest of the range and on the desert slope, the Nevadan Biotic Province is represented by the sagebrush scrub association. No mammals can be considered typical of this region.

The Southern Desert Biotic Province occurs below 6000 feet elevation on the interior slope of the range, and markedly influences the mammal fauna of this slope. Twenty-one species of mammals are typical of this Province.

SCIENTIFIC AND COMMON NAMES OF PLANTS MENTIONED IN THIS REPORT

_Pinus lambertiana_ Sugar Pine _P. monophylla_ One-leaf Pinyon _P. ponderosa_ Yellow Pine _P. contorta_ Lodge-pole Pine _Pseudotsuga macrocarpa_ Big-cone Spruce _Abies concolor_ White Fir _Libocedrus decurrens_ Incense-Cedar _Juniperus californica_ Juniper _Ephedra sp._ Desert-Tea _Bromus sp._ Brome Grass _Yucca Whipplei_ Spanish Bayonet _Y. brevifolia_ Joshua Tree _Salix sp._ Willow _Alnus rhombifolia_ Alder _Castanopsis sempervirens_ Chinquapin _Quercus Kelloggii_ California Black Oak _Q. agrifolia_ California Live Oak _Q. dumosa_ Scrub Oak _Eriogonum fasciculatum_ California Buckwheat _Umbellularia californica_ Bay, California-laurel _Ribes nevadense_ Gooseberry _R. indecorum_ Currant _R. Roezlii_ Currant _Plantanus racemosa_ Sycamore _Rubus vitifolius_ Western Blackberry _Cercocarpus ledifolius_ Mountain Mahogany _C. betuloides_ Mountain Mahogany _Adenostoma fasciculatum_ Greasewood _Purshia glandulosa_ Antelope-brush _Prunus virginiana_ Choke Cherry _P. ilicifolia_ Holly-leaved Cherry _Larrea divaricata_ Creosote Bush _Rhus diversiloba_ Poisonoak _R. trilobata_ Squaw Bush _R. laurina_ Laurel Sumac _R. integrifolia_ Lemonadeberry _R. ovata_ Sugarbush _Rhamnus crocea_ Buckthorn _Ceanothus sp._ Lilac _C. cordulatus_ Snow-brush _Fremontia californica_ California Slippery-elm _Opuntia occidentalis_ Prickly-pear _Arctostaphylos sp._ Manzanita _Salvia mellifera_ Black Sage _S. apiana_ White Sage _Lycium Andersonii_ Box-thorn _Haplopappus squarosus_ _Chrysothamnus nauseosus_ Rabbitbrush _Baccharis sp._ Mule Fat _Franseria dumosa_ Burroweed _Artemisia tridentata_ Basin Sagebrush _A. californica_ Coastal Sagebrush _Lepidospartum squamatum_ Scale-broom _L. latisquamatum_ Scale-broom _Tetradymia spinosa_ Cotton-thorn

Coastal Sage Scrub Association

MAJOR PLANTS

_Artemisia californica_ _Salvia apiana_ _Salvia mellifera_ _Eriogonum fasciculatum_ _Rhus integrifolia_ _Opuntia occidentalis_ _Haploppapus squarrosus_

This association is restricted to the Pacific base of the range, is typical on the alluvium at the bases of the coastal foothills, and usually grades into the chaparral at about 1800 feet elevation. When seen from above, the rather level terrain of the association is broken sharply at the mouths of canyons by dry washes, and is limited below, to the south, by cultivated land. The coastal sagebrush is the most characteristic plant of this association, occurring in all undisturbed parts of the area.

There are several habitats within the coastal sage scrub association. These differ from one another chiefly on the basis of soil type. The soil of the rather level sageland in most places is rocky or gravelly, or, as adjacent to washes, it is finely sandy in texture, and supports the major plants of the association. Most of the eroded adobe banks at the bases of the foothills support these same plants, with white sage being the dominant species. Locally, as in damp hollows or cleared areas, there is grassland. Jumbles of boulders, sand, gravel, and steep cutbanks, are characteristic of the channels of dry washes, these areas supporting sparse vegetation. The fauna and flora of the washes are distinct from those of surrounding sage flats. Because they are included within the geographic limits of the coastal sage belt, however, the washes are discussed along with this association.

The abruptness with which one habitat gives way to another in this association causes sharp dividing lines between the local ranges of certain mammals. For example, in trap lines transecting dry washes and level sageland two assemblages of rodents were found. That part of the line amid the boulders and cutbanks of the wash took mostly _Peromyscus eremicus fraterculus_ and _Neotoma lepida intermedia_, while _Perognathus fallax fallax_, _Dipodomys agilis agilis_, and _Peromyscus maniculatus gambeli_ were taken in the adjacent sage flats. The steep adobe slopes of the foothills, which constitute the upper part of the coastal sage scrub association, are commonly inhabited by _Peromyscus californicus insignis_, which rarely occurs in the level tracts of sage a few yards away. Thus, this association is not homogeneous with regard to its rodent population; many of these species have local and discontinuous distributions.

The following list gives the results of about 500 trap nights (a trap night equals one trap set out for one night) in typical coastal sage-scrub association one-half mile southwest of the mouth of San Antonio Canyon, at 1700 feet elevation.

TABLE 2.--YIELD OF 500 TRAP-NIGHTS IN THE COASTAL SAGE SCRUB ASSOCIATION.

====================================================================== | Number | Per cent | | of total --------------------------------------------------+--------+---------- Perognathus fallax fallax | 31 | 30.7 Dipodomys agilis agilis | 20 | 19.8 Reithrodontomys megalotis longicaudus | 4 | 4.0 Peromyscus californicus insignis | 4 | 4.0 P. eremicus fraterculus | 7 | 6.9 P. maniculatus gambeli | 20 | 19.8 Neotoma lepida intermedia | 9 | 8.8 N. fuscipes macrotis | 2 | 2.0 Microtus californicus sanctidiegi | 4 | 4.0 --------------------------------------------------+--------+----------

The list below indicates the catch in 200 trap nights in San Antonio Wash, at 1700 feet elevation and within the realm of the coastal sage; all of the traps were set in rocky and sandy main channels of the wash.

TABLE 3.--YIELD OF 200 TRAP-NIGHTS IN SAN ANTONIO WASH.

====================================================================== | Number | Per cent | | of total --------------------------------------------------+--------+---------- Perognathus fallax fallax | 2 | 5.1 Peromyscus californicus insignis | 2 | 5.1 P. eremicus fraterculus | 26 | 66.7 Neotoma lepida intermedia | 9 | 23.1 --------------------------------------------------+--------+----------

The prickly-pear cactus is of obvious importance to certain mammals of the coastal sage belt. This cactus is most common in disturbed areas such as sandy flats bordering washes, eroded adobe banks, and land once cleared by man. In these areas it is often the dominant plant with respect to area covered, usually growing in dense patches each covering approximately 150 square feet. It provides substitute nesting sites for _Neotoma lepida_ in areas devoid of rock piles, and is probably the major factor governing the distribution of this wood rat in the sageland. Cottontails and brush rabbits use prickly-pear cactus extensively as refuge. Their forms and short burrows can be seen beneath many of the clumps of cactus.

This cactus serves as food for many mammals at least in the fruiting period in the fall. Usually only the fruit is eaten, but some pads are chewed by rabbits. The fruit or seeds of this plant are eaten by striped skunks, gray foxes, coyotes, pocket mice, kangaroo rats, wood rats, and probably white-footed mice.

The coyote is the dominant carnivore of the coastal sage flats. Many individuals spend the day in the adjacent chaparral-covered foothills and travel down into the flats at night to forage.

Southern Oak Woodland Association

MAJOR PLANTS

_Alnus rhombifolia_ _Quercus agrifolia_ _Ribes indecorum_ _Rhus integrifolia_ _Rhus ovata_ _Rhus trilobata_

This association is limited to the Pacific slope of the mountain range, occurs in the mouths of canyons and on the floors of canyons, and extends up the larger canyons to 4000 feet elevation or higher. In a few areas on the flats at the coastal base of the range the oaks replace the coastal sage.

The large oaks forming an overhead canopy and the lack of much undergrowth give the oak woodland a shaded parklike appearance. Few brushy or herbaceous plants grow in the mull-laden soil beneath the oaks. Some grasses, however, are present locally.

Two habitats are found in the oak woodland: the pure oak woodland and the riparian. Much of the oak woodland is in canyons and therefore near streams or seepages. The larger streams have bordering growths of alders, willows, and blackberries, inhabited by meadow mice and shrews that are normally absent from the adjacent oak woodland. NEOTOMA FUSCIPES MACROTIS and PEROMYSCUS CALIFORNICUS INSIGNIS are commonly found in the riparian habitat, and _Peromyscus boylii_ probably reaches peak abundance in the stream-side thickets and tangles of plant debris.

The rather open floor of the oak woodland is relatively devoid of mammal life. _Peromyscus californicus_ and _Peromyscus boylii_, the only ground-dwelling rodents commonly found here, usually are taken near the limited areas of brushy growth, or the shelter afforded by logs and fallen branches. The paucity of shelter for small mammals seems to be an important factor limiting rodent populations in the oak woodland.

In the foothills of the San Gabriels the gray squirrel is restricted to the oak woodland, even though this association may be represented by only a narrow strip of canyon bottom oak trees. The presence or absence of "bridges" of oak woodland between mountains which are centers of gray squirrel populations and nearby ranges has probably been a major factor influencing the present geographic distribution of this animal.

The raccoon is the most abundant carnivore of the oak woodland, being especially common in the riparian habitat.

Chaparral Association

MAJOR PLANTS

_Adenostoma fasciculatum_ _Rhamnus crocea_ _Quercus dumosa_ _Cercocarpus betuloides_ _Yucca Whipplei_ _Prunus ilicifolia_ _Ceanothus sp._ _Arctostaphylos sp._ _Umbellularia californica_

This association is characteristic of the Pacific slope of the San Gabriels and extends from roughly 2000 feet elevation to 5000 or 6000 feet elevation. The ecotone between the chaparral and yellow pine forest associations covers a broad elevational belt, with chaparral following dry slopes up into coniferous forests, and conifers extending down north slopes surrounded by chaparral.

The chaparral association is characterized by tracts of dense brushy plants. These plants are from three to ten feet tall, their interlacing branches often forming nearly impenetrable thickets. Typically little herbaceous growth is present beneath the chaparral, the ground being covered with varying amounts of mull.

The effects of fire, slope, exposure, and elevation, make the chaparral association extremely varied with regard to habitats or plant formations. There are nearly pure stands of greasewood on the lower arid slopes; scrub oak, sumac, and lilac clothe less dry exposures; scrub oak and bay trees occur commonly amid granite talus; and locally groves of bigcone-spruce are found. Because of the many habitats present, and the difficulty of collecting in the chaparral, less was learned of the ecology of the mammals in this association than of those occurring elsewhere. The distribution of several chaparral-inhabiting mammals seems to be influenced by the distribution of locally characteristic plants, for example oak and bay woodland, or greasewood chaparral.

Several habitats within the chaparral community support few species of mammals and few individuals. Possibly the compact, rocky nature of the soil limits burrowing rodents, and the lack of herbaceous growth limits the food supply. Steep rocky slopes in San Antonio Canyon grown to mountain-mahogany and scrub oak were sparsely populated by _Peromyscus boylii rowleyi_, _Peromyscus californicus insignis_, and _Neotoma fuscipes macrotis_. Fifty traps set on such a slope for one night caught only three _Peromyscus_. Traps set in tracts of greasewood brush on dry south slopes at the head of Cow Canyon produced only California mice, _Peromyscus californicus insignis_ Rhoads.

Following is a list of the mammals taken in the course of approximately 600 trap nights in the lower parts of the chaparral belt. All of the traps were set on slopes in San Antonio Canyon below 4000 feet elevation. The list gives a general indication of the relative numbers of rodents inhabiting one chaparral habitat: the arid greasewood-covered south slopes of the lower chaparral belt.

TABLE 4.--YIELD OF 600 TRAP-NIGHTS IN GREASEWOOD CHAPARRAL.

====================================================================== | Number | Per cent | | of total --------------------------------------------------+--------+---------- Perognathus californicus dispar | 4 | 10.0 Dipodomys agilis agilis | 4 | 10.0 Peromyscus californicus insignis | 25 | 62.5 Neotoma fuscipes macrotis | 7 | 17.5 --------------------------------------------------+--------+----------

Heteromyids are evidently absent from the upper parts of the chaparral association, but cricetid rodents are common there beneath heavy clumps of lilac and in the talus beneath oaks and bay trees. The following list gives the mammals taken in the course of about 200 trap nights in the granite talus one half mile northwest of the mouth of Icehouse Canyon, at 5200 feet elevation.

TABLE 5.--YIELD OF 200 TRAP-NIGHTS IN THE UPPER PART OF THE CHAPARRAL ASSOCIATION.

====================================================================== | Number | Per cent | | of total --------------------------------------------------+--------+---------- Eutamias merriami merriami | 3 | 6.3 Peromyscus boylii rowleyi | 38 | 79.2 Neotoma lepida intermedia | 2 | 4.2 Neotoma fuscipes macrotis | 5 | 10.4 --------------------------------------------------+--------+----------

The gray fox is the dominant carnivore of the chaparral association and forages widely in all habitats.

Yellow Pine Forest Association

MAJOR PLANTS

_Pinus ponderosa_ _P. lambertiana_ _Libocedrus decurrens_ _Abies concolor_ _Quercus Kelloggii_ _Ribes nevadense_ _Ribes Roezlii_ _Arctostaphylos sp._ _Ceanothus cordulatus_

The crest of the range, from the upper limit of the chaparral association at roughly 6000 feet to the limited areas of boreal flora above 8500 feet elevation, is covered by yellow pine forests. On the desert slope of the range the coniferous forests which extend down to about 6000 feet represent the best development of this association, while the coniferous forests on the coastal side of the drainage divide are often more or less diluted by chaparral elements. For example, yellow pines on the Pacific face of Blue Ridge at 7000 feet elevation often grow in association with scrub oak and mountain-mahogany.

Few mammals are resident in the typical yellow pine forest as characterized by dense coniferous timber and little herbaceous or brushy growth. Here most of the species recorded actually find optimal conditions in an adjacent habitat. The forest probably harbors surplus individuals from adjacent preferred habitats, or, as in the case of chipmunks and ground squirrels, the forest often serves as forage ground while nearby brushy areas are utilized for breeding and shelter. The abundance of birds in the timber contrasts strikingly with the paucity of mammals there. The lack of a seed-producing understory, and the open duff-covered stretches of ground on which rodents would be extremely vulnerable to predation, probably in part account for the scarcity of rodents.

Within the general area encompassed by the yellow pine forest there are two major habitats, namely coniferous forest and chaparral. The species of plants comprising the chaparral of the Transition Life-zone are different from those comprising the chaparral of the Upper Sonoran Life-zone on the Pacific slope. In the chaparral of the Transition Life-zone, basin sagebrush and snowbrush grow in extensive patches in clearings in the timber. Dense thickets of choke cherry cover many damp hollows, and these thickets harbor the houses of _Neotoma fuscipes_. The food and shelter afforded by these chaparral areas importantly influence the local distribution of rodents: for example, _Dipodomys agilis_ and _Perognathus californicus_ in the yellow pine area are found only in association with chaparral, being completely absent from wooded areas.

The severe winter weather in this association must force many of the mammals into periods of inactivity. Probably during the long periods in the winter when snow covers the ground the heteromyids and sciurids remain below ground.

Pinyon-Juniper Woodland Association

MAJOR PLANTS

_Pinus monophylla_ _Juniperus californica_ _Quercus dumosa var. turbinella_ _Purshia glandulosa_ _Fremontia californica_ _Cercocarpus ledifolius_ _Yucca Whipplei_

In the San Gabriel Mountains this association is limited to the desert slope and reaches its lower limit at the bases of the foothills and extends up to the lower edge of the yellow pine forests. The altitudinal extent of the pinyon-juniper association is from roughly 4000 to 6000 feet elevation.

Several habitats are evident within the pinyon-juniper belt. On north slopes in the upper part of this association, scattered stands of pinyon pines are found with dense patches of scrub oak intervening, while on other such slopes a dense chaparral is present, consisting primarily of scrub oak, mountain-mahogany, and California slippery-elm. In this type of chaparral several hundred trap nights yielded only two rodent species: _Neotoma fuscipes simplex_ and _Peromyscus truei montipinoris_. There are few pinyons on the south slopes, especially in the lower parts of the association; many of these slopes are clothed with an open growth of manzanita and yucca, while northern exposures there support mostly scrub oak. Many of the flats of the pinyon belt are grown to basin sagebrush.

Following is a list of the mammals taken in about 400 trap nights at one locality in the pinyon-juniper association. The area supported a mixed growth of pinyon, scrub oak, mountain-mahogany, and antelope-brush, together with smaller brushy plants, and was at the head of Grandview Canyon, at an altitude of roughly 5000 feet.

TABLE 6.--YIELD OF 400 TRAP-NIGHTS IN THE PINYON-JUNIPER ASSOCIATION.

===================================================================== | Number | Per cent | | of total -------------------------------------------------+--------+---------- Perognathus fallax pallidus | 3 | 11.5 Dipodomys agilis fuscus | 9 | 34.6 Peromyscus truei montipinoris | 10 | 38.5 Neotoma fuscipes simplex | 4 | 15.4 -------------------------------------------------+--------+----------

Although Munz and Keck (1949:101) considered the pinyon-juniper belt as one association, on the desert slope of the San Gabriels pinyons and junipers do not generally grow on common ground; but rather the juniper belt represents a well defined habitat occurring between the pinyon covered slopes and the flats that support Joshua trees. Because the mammalian populations of the pinyon belt and the juniper belt are somewhat different, the mammals of these areas are most conveniently taken up separately.

In the juniper belt the juniper tree is of marked ecologic significance; the distribution of _Peromyscus truei_ and _Neotoma fuscipes_ is determined here by the presence of junipers. At certain times of year the fruit of this plant is eaten by coyotes, kangaroo rats, and wood rats.

The list below indicates the results of approximately 500 trap nights in the juniper belt near Mescal Canyon, between 4000 and 5000 feet elevation.

TABLE 7.--YIELD OF 500 TRAP-NIGHTS IN THE JUNIPER BELT.

====================================================================== | Number | Per cent | | of total --------------------------------------------------+--------+---------- Perognathus fallax pallidus | 16 | 16.7 Dipodomys merriami merriami | 3 | 3.1 Dipodomys panamintinus mohavensis | 36 | 37.5 Peromyscus truei montipinoris | 22 | 22.9 Peromyscus maniculatus sonoriensis | 12 | 12.5 Neotoma lepida lepida | 2 | 2.1 Neotoma fuscipes simplex | 2 | 2.1 Onychomys torridus pulcher | 3 | 3.1 --------------------------------------------------+--------+----------

PLATE 1

PLATE 2

PLATE 3

PLATE 4

The biota of the washes that cut through the juniper belt in and below many of the larger canyons differs from that of the surrounding juniper-clad benches. Because the washes are in the same geographic area as the juniper belt they are discussed together. These washes on desert slopes are densely populated by rodents derived from adjacent areas, and support vegetation typical of higher floral belts in association with xerophytic, typically desert, species. In a sense, the washes serve to mix up the mammals of adjacent areas. For example, _Onychomys torridus pulcher_ and _Peromyscus eremicus eremicus_, which are mammals typical of the desert, were found in Mescal Wash above their usual desert range; and _Peromyscus californicus insignis_ and _Peromyscus boylii rowleyi_, which are chaparral inhabiting mammals, were found in the wash far removed from their chaparral environment. Washes are evidently effective agents in facilitating the dispersal of certain species of mammals. It is easy to envision a species crossing hostile habitats _via_ dry washes to invade suitable niches in an area which is geographically and ecologically isolated from the original home of the species. Approximately 500 trap nights in Mescal Wash, at 4100 feet elevation, in the lower edge of the juniper belt, yielded the following mammals:

TABLE 8.--YIELD OF 500 TRAP-NIGHTS IN MESCAL WASH (DESERT SLOPE).

========================================================== | Number | Per cent | | of total --------------------------------------+--------+---------- Perognathus fallax pallidus | 5 | 4.5 Dipodomys panamintinus mohavensis | 43 | 38.7 Peromyscus californicus insignis | 3 | 2.7 Peromyscus truei montipinoris | 1 | .9 Peromyscus boylii rowleyi | 2 | 1.8 Peromyscus eremicus eremicus | 28 | 25.0 Peromyscus maniculatus sonoriensis | 23 | 20.5 Onychomys torridus pulcher | 4 | 3.5 Neotoma lepida lepida | 3 | 2.7 --------------------------------------+--------+----------

_Dipodomys panamintinus mohavensis_, _Neotoma fuscipes simplex_, and _Peromyscus truei montipinoris_ are probably the most characteristic mammals of the pinyon-juniper association.

Sagebrush Scrub Association

MAJOR PLANTS

_Bromus sp._ _Artemisia tridentata_ _Chrysothamnus nauseosus_ _Purshia 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 and _Haplopappus_. 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 for _Dipodomys agilis perplexus_ and _Perognathus californicus bernardinus_; and in Swarthout Valley _D. a. perplexus_, _Reithrodontomys megalotis longicaudus_, and _Lepus californicus deserticola_ are seemingly restricted to the sagebrush flats.

Joshua Tree Woodland Association

MAJOR PLANTS

_Yucca brevifolia_ _Lycium Andersonii_ _Eriogonum fasciculatum_ _Tetradymia spinosa_ _Ephedra 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 of _Dipodomys panamintinus_ or _Dipodomys merriami_, and those burrows abandoned by kangaroo rats are used as retreats by _Onychomys torridus_ and _Peromyscus 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.

====================================================== | Number | Per cent | | of total -----------------------------------+--------+--------- Dipodomys panamintinus mohavensis | 36 | 59.0 Dipodomys merriami merriami | 15 | 24.6 Onychomys torridus pulcher | 4 | 6.6 Peromyscus maniculatus gambeli | 6 | 9.8 -----------------------------------+--------+---------

Populations of _Dipodomys merriami_ and _D. panamintinus_ fluctuate widely, possibly in response to weather cycles. In November of 1948 trapping in the Joshua belt showed that _panamintinus_ outnumbered _merriami_ approximately three to one, whereas in December of 1951, after a succession of unusually dry years, _merriami_ was the more numerous. Further, _merriami_ occurred in the lower parts of the juniper belt in 1951 where in 1948 it seemed to be absent.

_Dipodomys merriami merriami_ and _Onychomys torridus pulcher_ are diagnostic of the Joshua tree woodland association in the San Gabriel Mountains area, since few individuals of either species occur outside of this association.

ACCOUNTS OF SPECIES

Family DIDELPHIDAE

=Didelphis marsupialis virginiana= Kerr

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 occultus= Grinnell 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 parvidens= Jackson

Dusky Shrew

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

=Sorex ornatus ornatus= Merriam

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 sociabilis= H. 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 by _evotis_. 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 and _Baccharis_. 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. evotis_ usually first appeared just at dark, well after the pipistrelles and California myotis had begun foraging. The forage period of _evotis_ seemed 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 interior= Miller

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, probably _volans_, 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, _volans_ appeared 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 deg.F. The floor of the tunnel was covered with the hind wings of large moths of the genus _Catocala_; _volans_ probably hung in the cave while eating them.

The series of _volans_ from 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 of _volans_ from 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 this species 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 and _Baccharis_ near San Antonio Creek, but they did not fly so low or so near the vegetation as did _Myotis 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. Like _Myotis californicus_ this 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 active in 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 deg.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 bernardinus= Rhoads

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 coastal base 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 empty stomachs 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 captive _Myotis californicus_ in 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 pacificus= Merriam

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 of _Antrozous_ and _Tadarida_ was 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 family _Sphingidae_, and legs and parts of the heads of Jerusalem crickets (_Stenopelmatus fuscus_) were beneath an _Antrozous_ night-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 of _Antrozous_, and was once found with a colony of _Eptesicus_ near 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 bennettii= Gray

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 deserticola= Mearns

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.