Habitat Associations and Co-occurrence of Chihuahuan Desert Hares (Lepus californicus and L. callotis)

Black-tailed and white-sided jackrabbits (Lepus californicus and L. callotis) occur sympatrically throughout much of the Chihuahuan Desert; black-tailed jackrabbits are widely distributed, whereas white-sided jackrabbits are endemic to the Mexican Plateau. I measured abundance, distribution and habitat associations of each species in western Chihuahua, Mexico, during the winters of 1998 and 1999. No difference was observed in mean density; however, black-tailed jackrabbits were more abundant in semi-desert grasslands, whereas white-sided jackrabbits were most abundant in high elevation, plains grasslands. The occurrence of the two species was negatively correlated, a result of different habitat preferences or competition. Black-tailed jackrabbits were solitary, whereas white-sided jackrabbits were usually observed in pairs (74 and 58% of the time for 1998 and 1999, respectively). Dry conditions and heavier grazing pressure present in 1999 accentuated differences in characteristics of sites used and not used by jackrabbit species. The presence of black-tailed jackrabbits was positively associated with vegetation density in 1998 and positively associated with shrub density in 1999. White-sided jackrabbit presence was positively associated blue grama grasslands in 1999. Remaining open patches of desert grassland are important for the persistence of white-sided jackrabbit populations.