Sagebrush Soundscapes and the Effects of Gas-Field Sounds on Greater Sage-Grouse

Abstract

Greater Sage-Grouse (Centrocercus urophasianus) use elaborate acoustic and visual displays to attract and select mates, and females and chicks depend on acoustic communication during brood rearing. A potential threat to the grouse is sounds associated with human activity. During April, 2013–2020, we collected 17,825 hours of acoustic data in three different acoustic situations in the sagebrush of Wyoming: rural, undeveloped areas (6), at Greater Sage-Grouse leks in a natural-gas field (20), and near active machinery in that gas field (17). The average existing sound levels in undeveloped sagebrush areas were LAeq = 26 dB and LA50 = 20 dB, and the average background sound level was LA90 = 14 dB. These values are lower than previously reported, due in part to our use of more sensitive equipment as well as addressing the influence of the instruments’ electronic self-noise. LAeq and LA50 at leks in the gas field ranged from 25.5 to 33.7 dB and 20.5 to 31.3 dB, respectively, depending on the distance, number, and type of nearby activities. Sound levels at leks were correlated with trends in the number of grouse using the lek: the higher the sound level, the greater the likelihood of a decline. Thresholds above which declines occurred were LAeq = 31 dB and LA50 = 26 dB. Leks with LAeq > 31 dB and LA50 >26 dB, 100% and 91%, respectively, had declining trends. Our findings suggest that the current policy of limiting sound levels at leks to LA50 < 10 dB (or LAeq < 15 dB) over the background sound level is appropriate, if an accurate background level is used.