Potential distribution of American black bears in northwest Mexico and implications for their conservation Christian Alejandro Delfı´n-Alfonso 1,2,3 , Carlos Alberto Lo´ pez-Gonza´lez 1 , and Miguel Equihua 2 1 Facultad de Ciencias Naturales, Universidad Auto ´noma de Quere ´taro, Del. Santa Rosa Ja ´uregui, Santiago de Quere ´ taro, Quere ´taro, Me ´xico 2 Red Ambiente y Sustentabilidad, Instituto de Ecologı´a, A.C., Veracruz, Me ´xico Abstract: 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 5 582) 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. Key words: American black bear, distribution, ecological niche, Mexico, Sierra Madre Occidental, Sky Island, Ursus americanus Ursus 23(1):65–77 (2012) Numerous tools and approaches have been devel- oped to study species’ potential distribution (Guisan and Zimmermann 2000, Arau ´jo and Guisan 2006) and to identify factors that may explain and define such distributions in both geographical and ecological dimensions (Boydston and Lo ´ pez-Gonza ´lez 2005, Kambhampati and Peterson 2007). Large carnivores are excellent subjects for this type of study due to their large home ranges and their sensitivity to landscape change. Carnivores are environmentally sensitive because of their low fertility and density as well as their limited dispersal capability in open or trans- formed habitats (Alt et al. 1980, Weaver et al. 1996, Costello et al. 2001, Klenzendorf 2002). These characteristics also make carnivores a species group at risk from large-scale changes in landscape patterns. This is the case of the American black bear (Ursus americanus). Through its evolutionary history, its distribution has been associated with the temperate forests of North America, spanning from the limits of the boreal vegetation in Northern Alaska to highland temperate forests on the edge of tropical vegetation in Mexico (Kolenosky and Strathearn 1987, Ken- nedy et al. 2002). In Mexico, it is one of the few large carnivores still present and almost exclusively associated with temperate mountain forests of the northwest and northeast regions (Wooding and Ward 1997, Costello et al. 2001). However, there are important geographical differences between proposed models concerning the probable distribu- tion of the black bear in Mexico (compare Hall 1981 3 cada7305@gmail.com 65