Arthropod Prey‐Predator Ratios in a Sagebrush Habitat: Methodological and Ecological Implications

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Abstract
A 3—yr study of arthropod prey—predator ratios, based on species richness and density, was conducted in undisturbed and in intensively managed sagebrush habitats in southeastern Wyoming. Using simulated data sets, Bartlett's regression generated significantly more accurate prey—predator ratios than either simple ratios or ordinary least squares, so Bartlett's regression was used for analysis of field data. Both richness and density ratios were generally constant across taxonomic groups (insects, arachnids, and all arthropods) in both undisturbed and managed habitats. Prey—predator richness ratios ranged from 1.18 to 2.36 and were considered temporally and spatially constant in undisturbed habitats. The more sensitive density ratios ranged from 2.23 to 7.77, and showed significant variation in time and space. Herbicide application significantly decreased the prey—predator richness ratios in the treatment year, but the ratios increased the following year. Mowing also decreased richness ratios, but the changes were not significant. Although spatial and temporal heterogeneity prevented determination of valid control for assessing the impact of disturbances on most density ratios, the management practices appeared to have increased prey—predator ratios in the treatment and post treatment years.