Grazing by non-native ungulates negatively impacts vegetation important to a native species of concern

Non-native grazers compete with native species across the globe. In the northwestern Great Basin of the western United States competition among livestock, feral horses, and Greater Sage-grouse has been the subject of numerous legal actions and management policies, yet spatially explicit temporal data documenting the details of this competition are lacking. We present a novel approach to studying the composition of the herbaceous understory across three study areas within the Great Basin with different historic and contemporary grazing regimes.  We surveyed the landscape using distance sampling for livestock and horse feces as an index of use. In addition, we surveyed the herbaceous understory of random sites as well as sites chosen by female Greater Sage-grouse to nest and brood their chicks. We used a novel Bayesian hierarchical modeling framework to link vegetation metrics with the spatial-temporal distribution of horses and livestock while accounting for observation error. When lives...