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.