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