干旱区生态环境知识资源中心

Habitat assessment models currently widely used by wildlife managers lack a quantitative descriptor of escape terrain used by desert bighorn sheep (Ovis canadensis). We examined habitat patch characteristics associated with 14 augmented, reintroduced, remnant, and extirpated desert bighorn sheep populations in Arizona using Geographic Information System (GIS) technology to determine relationships between escape terrain area and configuration and estimated population size, density, and production. Total bighorn, female, and lamb population sizes were positively correlated with measures of escape terrain area and configuration, including number and size of patches and percent of landscape, indicating that abundance was greater in more heterogeneous landscapes. Populations using smaller patches were more vulnerable to extirpation than those using larger patches. Populations with greater than or equal to10 animals per km(2) of escape terrain and patches with less than or equal to10 km(2) Of escape terrain were more variable, suggesting the likelihood of wider population fluctuations compared to populations tending to occupy larger patches at lower densities. Consistent with theory, density and relative productivity were independent of habitat patch and population size, except that variability of lamb density was negatively correlated with escape terrain patch size. Variability of total, female, and lamb population density increased directly with density. We hypothesized that area and configuration of escape terrain are primary correlates of desert bighorn sheep population size in Arizona, and management efforts to restore or augment desert bighorn sheep populations on isolated habitat patches might best focus on locations with at least 15-km(2) escape terrain. Habitat evaluation using CIS technology should provide a useful preliminary, quantitative step in making decisions regarding habitat quality and management intervention for desert bighorn sheep populations and for translocations into historically occupied vacant areas.