Detection and analysis of community response to threats using a novel soundscape approach

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Parks Marion, Biological Sciences, Western Michigan University, Lansing, MI and Sharon A. Gill, Biological Sciences, Western Michigan University, Kalamazoo, MI

Background/Question/Methods
What happens to the collective signaling within communities when species are confronted with threats to survival and reproduction? Many species in the community treat as threats the presence of avian predators, brood parasites, and humans, which may lead to changes in the acoustic signaling of individual species. Complex and unique information is transmitted via these responses and this information can be interpreted and acted on by other individuals, thus leading to a community level acoustic response. Limited understanding exists of community-level signaling changes to threats, yet such information may expand the study of community behavior and guide future lines of inquiry on predator/prey interactions. We tested the hypothesis that community response will differ with threat type as measured by a suite of acoustic indices. We presented three threat treatments (avian predator, brood parasite, and human) using playback of species-specific sounds paired with models in two habitat settings: forest and grassland. We recorded the vocal responses of the community adjacent to the site of threat presentation and 45 m away to analyze whether community responses differ with distance from the threat. The recordings were analyzed using a suite of acoustic indices and compared using a linear mixed model approach.
Results/Conclusions
Preliminary analysis showed significant differences in acoustic indices across treatments and that the patterns varied with the index applied. Our results indicated different community responses to treatment, consistent with observed changes in community behavior. Timing of response emerged as important in some indices with differences between the before and during/after threat periods. Habitat effects were also significantly different in two index measures, but also confounded treatment effects in the analysis. Thus, community-level patterns were detected in signaling responses to threat as revealed by application of acoustic indices with the avian predators producing the greatest changes in community response in most indices. Further experimentation and analysis may reveal specific patterns in response to threat. Nevertheless, these results build our understanding of acoustic indices as analytical tools and support their use in community behavior analysis. Detecting community level acoustic events has the potential to inform our understanding of threat response by communities and expand our ability to utilize acoustic monitoring data.