Cattle distribution, habitats, and diets in the Sierra Nevada of California.

Abstract

Cattle have been used to control shrubs following timber harvesting in the Sierra Nevada of California, although their effectiveness varies between sites. Although cattle home ranges, habitat use, and diets are known for many forested ecosystems, the coniferous forests of the Sierra Nevada are different because shrubs are the most common understory species, with fewer herbaceous species than elsewhere in the western United States. As a first step in evaluating factors that influence cattle distribution and their potential effectiveness in controlling competing vegetation in the Sierra Nevada, we used radio-telemetry collars on cows to determine their home ranges and habitat use patterns. Mean home range size was 162.80 ha in 1986 and 278.83 ha in 1987. When choosing home ranges, cattle showed the greatest affinity for riparian habitat, followed by clearcuts, second-growth forest, and burned areas. Distances from streams to cattle locations were significantly (p<0.01) less (mean 59.3 m in 1986, and (mean = 60.1 m in 1987) than were distances from streams to random points (mean= 130.4 m). Based on microhistological analysis of fecal fragments, cattle diets included seeded grasses and shrubs mostly from upland sites, but fortes primarily from riparian sites. We suggest the need for water and the relative lack of herbaceous forage in the understory of mixed-conifer forests in the Sierra Nevada resulted in the strong, summer-long preference for riparian habitats. The effectiveness of grazing in controlling competing vegetation following timber harvest may be related to the proximity of the clearcuts to riparian habitats but this specific hypothesis remains to be tested.