Feral horse (Equus ferus caballus) grazing can alter arid shrubland habitat in the western United States to the detriment of sympatric wildlife species, including the greater sage-grouse (Centrocercus urophasianus). To date, studies of horse-influenced habitat alteration have only occurred in a few locations and have infrequently represented gradients of horse use. We investigated whether greater sage-grouse habitat quality metrics were negatively associated with feral horse use in southcentral Wyoming, USA. We also tested whether utilization distributions generated from feral horses tracked with global position system transmitters were correlated with dung pile density, our index of horse use. Dung pile density did not vary among utilization distribution levels, indicating utilization distributions were a poor predictor of cumulative horse use. Bare ground increased with dung pile density (β = 0.06, 85% CI = 0.04–0.18), and grass height exhibited a threshold response and began to decline after 638 piles/ha. Other habitat metrics including percent shrub cover, native perennial grass cover, and visual obstruction were better explained by topographic and temporal variation. Our results suggest that herd size reduction may limit soil erosion potential and improve desired herbaceous structure, though additional management actions regarding feral horse use are needed to sustain high-quality greater sage-grouse habitat.

野马（Equus ferus caballus）放牧会改变美国西部干旱灌木林的栖息地，从而损害同域野生动物物种，包括大鼠尾草（Centrocercus urophasianus ））。迄今为止，马影响栖息地改变的研究只发生在少数几个地方，很少代表马使用的梯度。我们调查了更大的鼠尾草栖息地质量指标是否与美国怀俄明州中南部的野马使用呈负相关。我们还测试了使用全球定位系统发射器跟踪的野马产生的利用率分布是否与粪便密度相关，我们的马使用指数。粪便密度在利用率分布水平之间没有变化，表明利用率分布是累积马使用量的不良预测指标。裸地随粪堆密度增加（β = 0.06，85% CI = 0.04–0.18），草高表现出阈值响应，并在 638 堆/公顷后开始下降。其他栖息地指标，包括灌木覆盖百分比、本地多年生草覆盖和视觉障碍，可以通过地形和时间变化更好地解释。我们的研究结果表明，畜群规模的减少可能会限制土壤侵蚀的可能性并改善所需的草本结构，尽管需要对野马的使用采取额外的管理措施来维持高质量的鼠尾草松鸡栖息地。