I am broadly interested in understanding if and how animals adapt to changes in the local environment. As a scientist, it is my goal to understand the effects of human-driven environmental changes in order to develop data-driven solutions to conserve biodiversity and preserve ecosystem integrity.
Noise associated with human activity is widespread and expanding rapidly in terrestrial environments, but there is still much to learn about its effects on animals. These effects, which can include behavioral change, physiological stress, and the masking of communication signals and predators’ sounds, can be difficult to study because noise is typically accompanied by a host of other environmental changes.
Noise Introduction Study
For my dissertation research, I played back recorded continuous and intermittent anthropogenic sounds associated with natural gas drilling and roads at leks of Greater Sage-Grouse to determine the effect of introduced noise on lek attendance, stress, and strutting behavior. For 3 breeding seasons, I monitored sage-grouse attendance leks with and without noise.
Noise and Lek Attendance
Peak male attendance (i.e., abundance) at leks experimentally treated with noise from natural-gas drilling and roads decreased 29% and 73% respectively relative to paired controls. Decreases in abundance at leks treated with noise occurred in the first year of the study and were sustained throughout the experiment. There was limited evidence for an effect of noise playback on peak female attendance at leks or male attendance the year after the experiment ended.
Noise and Strutting Behavior
I also investigated whether male Greater Sage-Grouse (Centrocercus urophasianus) adjust the repetition and timing of their strut displays in response to playback of noise associated with natural gas development. I compared the signaling behavior of male sage-grouse on leks with long-term drilling and road noise playback to that of males on similar leks with no noise playback. Males exposed to long-term drilling noise playback strutted at higher rates and in longer bouts than males on control leks while males on road noise leks strutted at lower rates and in shorter bouts than males on control leks; these differences were only observed during close courtship, when strut rate is most important in influencing female mate choice. I also compared the strut timing of individuals during noisy and quiet periods during short-term playback of intermittent traffic noise. Males strutted less struts overall during noisy periods, but male behavior was related to female proximity. Males were not closely approached by females strutted less during noisy periods than quiet periods, but males that engaged in close courtship with females strutted at similar rates during noisy and quiet periods, even when females were far away
Noise and Stress
My collaborators and I also non-invasively measured immunoreactive corticosterone metabolites from fecal samples (FCMs) of males on both noise-treated and control leks in two breeding seasons. We found strong support for an impact of noise playback on stress levels, with 16.7% higher mean FCM levels in samples from noise leks compared with samples from paired control leks.
To quantify the potential for noise from natural gas infrastructure to mask sage-grouse vocalizations over both long and short distances, I analyzed the individual notes of mating vocalizations produced by Greater Sage-Grouse (Centrocercus urophasianus) and recordings of such noise. Noise produced by natural gas infrastructure is predicted to mask sage-grouse vocalizations substantially, reducing the active space of detection and discrimination of all vocalization components, and particularly impacting notes that are low frequency and low amplitude.
This study suggests that sage-grouse avoid leks with anthropogenic noise and that intermittent noise has a greater effect on attendance than continuous noise. Introduced noise is likely to cause substantial masking of sage-grouse vocalizations, which could increase the difficulty of mate assessment for lekking sage-grouse. However, masking is not likely to be the only mechanism of noise impact on this species as significant impacts to Greater Sage-Grouse populations were measured at noise levels that predict little to no masking. Sage-grouse may at least partially reduce masking impacts through behavioral plasticity, by modifying the timing and repetition of their struts to increase signal transmission.
The results of this study suggest that limiting noise production may help reduce the impacts of anthropogenic development on sensitive Greater Sage-Grouse populations.