Part 14

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

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

Family CRICETIDAE

=Reithrodontomys megalotis longicaudus= (Baird)

Western Harvest Mouse

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

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

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

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

=Peromyscus eremicus eremicus= (Baird)

Cactus Mouse

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

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

=Peromyscus eremicus fraterculus= (Miller)

Cactus Mouse

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

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

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

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

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

=Peromyscus californicus insignis= Rhoads

California Mouse

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

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

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

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

=Peromyscus maniculatus gambeli= (Baird)

Deer Mouse