Tamaño poblacional del oso negro (Ursus americanus) en dos Islas del Cielo del Noreste de Sonora, México.

Resumen The black bear is an endangered species in Mexico, like the majority of the large carnivores they are distributed in small and isolated populations and thus their conservation depends on understanding their population status. During 2009, we estimated the abundance and density of the black bear in Sierra de Ajos and Sierra de San Luis in the Northeast Sonora, using camera traps. We defined patches (Sierras) as a combination of elevation and vegetation types in this part of the range. We extrapolated the densities to patch area to estimate population size, obtaining a density of 14.0 ind/100 km 2 in San Luis and 2.0 ind/100 km 2 in Ajos and a population size of 218 and 24 individuals respectively. Sierra de San Luis is a larger patch than Sierra de Ajos, which influences directly the population size directly. Furthermore, Sierra de Ajos is isolated from other Sky Islands, resembling a sinkhole population with no evidence for reproduction. It is necessary to continue monitoring black bear populations of the Sky Islands, to determine population trends and related factors that cause the variation of population size among the Sky Islands.