Small Mammal Community in a Juniper-Woodland Sagebrush-Grassland Mosaic in Southwestern Wyoming

Abstract

We sampled small mammal species in four distinct habitat types in a pinyon-juniper woodland and sagebrush-grassland mosaic in southwestern Wyoming. The sagebrush-grassland, pinyon-juniper woodland, pinyon-juniper rocky slope, and pinyon-juniper cliff habitats were identified as common components of the landscape. We used sherman live-traps to capture small mammals in the sagebrush-grasslands (n = 10 sites), pinyon-juniper woodlands (n = 10 sites), pinyonjuniper rocky slopes (n = 7 sites), pinyon-juniper cliffs (n = 7 sites) habitat types to identify the small mammal community and determine macrohabitat associations of the more abundant species. We measured six habitat variables at random points throughout each site to determine a habitat complexity index (HCI) for each habitat type based on structural diversity. The small mammal community of the combined four habitats was composed of 11 species with deer mice (Peromyscus maniculatus) being the most abundant species in all four habitats. Next to deer mice, the least chipmunk (Tamias minimus) was the most abundant species in three of four habitat types. The least chipmunk and cliff chipmunk (T. dorsalis) exhibited similar abundances in the cliff habitat type. The pinyon-juniper woodland, the most complex habitat (HCI = 1.74), had the second lowest small mammal diversity (0.583); only sagebrush had lower diversity. The cliff habitat type had the highest species richness (S = 8), highest diversity (H' = 1.011) and evenness (J' = 0.49). We did not find a correlation between habitat complexity and small mammal diversity although we did find a significant relationship (P ≤ 0.01) between small mammal diversity and the percentage of ground covered by rock. Our findings suggest the importance of cliff habitat in maintaining small mammal diversity in the pinyon-juniper and sagebrush-grassland mosaic in southwestern Wyoming.