Behnke Tessa, Street Phillip, Davies Scott, Ouyang Jenny Q, Sedinger James S
Program in Ecology, Evolution, and Conservation Biology University of Nevada-Reno Reno Nevada USA.
Department of Natural Resources and Environmental Science University of Nevada-Reno Reno Nevada USA.
Ecol Evol. 2022 Sep 20;12(9):e9325. doi: 10.1002/ece3.9325. eCollection 2022 Sep.
Non-native ungulate grazing has negatively impacted native species across the globe, leading to massive loss of biodiversity and ecosystem services. Despite their pervasiveness, interactions between non-native grazers and native species are not fully understood. We often observe declines in demography or survival of these native species, but lack understanding about the mechanisms underlying these declines. Physiological stress represents one mechanism of (mal)adaptation, but data are sparse. We investigated glucocorticoid levels in a native avian herbivore exposed to different intensities of non-native grazing in the cold desert Great Basin ecosystem, USA. We measured corticosterone, a glucocorticoid in feathers for a large sample ( = 280) of female greater sage-grouse () from three study areas in Northern Nevada and Southern Oregon with different grazing regimes of livestock and feral horses. We found that greater feral horse density was associated with higher corticosterone levels, and this effect was exacerbated by drought conditions. Livestock grazing produced similar results; however, there was more model uncertainty about the livestock effect. Subsequent nesting success was lower with increased feather corticosterone, but corticosterone levels were not predictive of other vital rates. Our results indicate a physiological response by sage-grouse to grazing pressure from non-native grazers. We found substantial among-individual variation in the strength of the response. These adverse effects were intensified during unfavorable weather events, highlighting the need to reevaluate management strategies in the face of climate change.
非本地有蹄类动物的放牧对全球范围内的本地物种产生了负面影响，导致生物多样性和生态系统服务的大量丧失。尽管它们很普遍，但非本地食草动物与本地物种之间的相互作用尚未完全了解。我们经常观察到这些本地物种的种群数量或存活率下降，但对这些下降背后的机制缺乏了解。生理应激是（不）适应的一种机制，但数据稀少。我们在美国大盆地寒冷沙漠生态系统中，对一种本地食草鸟类暴露于不同强度的非本地放牧情况下的糖皮质激素水平进行了调查。我们测量了来自内华达州北部和俄勒冈州南部三个研究区域的大量雌性艾草松鸡（样本量(n = 280)）羽毛中的糖皮质激素皮质酮，这些区域有着不同的家畜和野马放牧模式。我们发现，野马密度越大，皮质酮水平越高，而且干旱条件会加剧这种影响。家畜放牧也产生了类似的结果；然而，关于家畜影响的模型不确定性更大。随着羽毛皮质酮水平的升高，随后的筑巢成功率降低，但皮质酮水平并不能预测其他关键率。我们的结果表明，艾草松鸡对非本地食草动物的放牧压力产生了生理反应。我们发现个体之间的反应强度存在很大差异。在不利的天气事件中，这些不利影响会加剧，这凸显了在面对气候变化时重新评估管理策略的必要性。
