Mammals of the San Gabriel Mountains of California Part 6

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 compet.i.tion offered there by _Eutamias merriami_, or because the rocky nature of the soil there rendered burrowing difficult.

Although observed less often in winter than in summer, this species is active all year. On February 6, 1949, in Mescal Wash, an antelope ground squirrel was foraging over the snow which was at least six inches deep.

These squirrels were attracted to the carca.s.ses 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 th.o.r.n.y bushes. This habit of regularly using observation posts is well developed in each species of ground squirrel found in the San Gabriels.

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

=Eutamias speciosus speciosus= (Merriam)

Lodgepole Chipmunk

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

On Blue Ridge these chipmunks used the uppermost stems of s...o...b..ush as vantage points, and when disturbed ran nimbly over th.o.r.n.y surfaces of the brush in seeking refuge in the tangled growth.

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

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

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

Merriam Chipmunk

The lower limit of the range of this species, on the coastal face of the range, is roughly coincident with that of manzanita--that is to say, it begins in the main belt of chaparral above the lower foothills. _E.

merriami_ seems to reach maximum abundance amid the granite talus, and scrub oak and _Pseudotsuga_ growth at the upper edge of the chaparral a.s.sociation. It was absent, however, from all but the lower fringe of the yellow pine forest a.s.sociation.

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

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

=Glaucomys sabrinus californicus= (Rhoads)

Northern Flying Squirrel

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

Family GEOMYIDAE

=Th.o.m.omys bottae pallescens= Rhoads

Valley Pocket Gopher

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

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

=Th.o.m.omys bottae neglectus= Bailey

Valley Pocket Gopher

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

On the desert slope they occur locally down into the pinyon-juniper belt.

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

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

=Th.o.m.omys bottae mohavensis= Grinnell

Valley Pocket Gopher

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

Family HETEROMYIDAE

=Perognathus fallax fallax= Merriam

San Diego Pocket Mouse

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

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

Individuals have been taken on nights of intermittent rain, yet none has been trapped on freezing nights.

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

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

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

=Perognathus fallax pallidus= Mearns

San Diego Pocket Mouse

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

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