干旱区生态环境知识资源中心

Defining areas of potential distribution for large carnivores is a critical step for generating conservation strategies. Ecological niche modelling is an important tool for identifying potential areas for conservation of carnivores, such as American black bears (Ursus americanus) in the Sierra Madre Occidental (SMOcc) and the Sky Islands (SI) region of Northwest Mexico. Our objective was to define areas and environmental factors that influence bear distribution and understand the causes of their absence. We used GARP (genetic algorithm for rule-set prediction) to define the potential area of distribution using historical and current records of black bear (n = 582) and 23 bioclimatic and physical variables. We obtained a consensus model with a high probability of occurrence and power prediction representing 80% of the SMOcc (221,078 km(2)), including the SI region (Sonora and Chihuahua deserts). The ecological dimensions of the model include temperate dry and mixed forest, low rainfall, low temperatures, and elevation above 1,500 m, with considerable slope variation. Information provided by residents of Aguascalientes, Chihuahua, Durango, and Zacatecas indicate that the species was extirpated in central and southwest Durango and Zacatecas about 50 years ago, coinciding with the use of 1080 poison (sodium fluoroacetate) to eradicate livestock predators, combined with habitat loss, fragmentation, and excessive hunting in the region. These factors precipitated the regional extirpation of the species. Areas such as those we have identified may be important sites for the reintroduction of black bears.