Collaborative Research: RUI: Direct and indirect effects of natural sounds on the structure of vertebrate insectivore communities

Scientists have long explained where particular species of animals are found by examining what we, as humans, see in the environment. For example, we know that the type and density of plants affect where sparrows can be found. However, many animals rely heavily on non-visual senses, such as hearing, when interacting with their surroundings and deciding where to live. Although the acoustic environment -- what animals hear -- may be important to many species, it remains largely unexplored as a force influencing where animals can be found. This project will examine the extent to which natural sounds, such as those generated by wind and water, influence where animals settle, how they interact with one another and, ultimately, how they structure entire communities. Focusing on birds and bats, the investigators will conduct a large-scale experiment in which they place many speakers in the forest to create 'phantom' oceans and rivers -- the sounds of moving water without the water itself. This will allow them to figure out how sounds can change the way in which species interact with their environment and with each other. Specifically, this study will test how noise can explain where animals live, how they behave, and the extent to which they are impacted by human-made noise generated, for example, along major highways. This study will also provide research opportunities for undergraduate students at small universities and will result in an 'Acoustics in Ecology and Evolution' workshop to teach young scientists how to incorporate acoustics into their own ecological field research.

Researchers will test for acoustic impacts on bird and bat communities in areas characterized by high levels of natural sounds from moving water (natural river and ocean surf sounds), low levels of natural sounds, high levels of artificially created natural sounds (phantom river and surf sounds), and spectrally-shifted, artificially created natural sounds. The latter two treatments will be generated via large-scale playbacks of sounds recorded elsewhere. The experimental approach of playing back natural sounds at different frequencies will allow researchers to parse the influence of acoustic masking versus more general effects of sounds (e.g., disturbance and distraction) on bird and bat behavior and on community structure. Researchers will also assess the potential role of low frequency natural sounds as acoustic beacons for habitat selection. Field work will entail a combination of behavioral experiments, bird, bat, arthropod and vegetation surveys, and spatially explicit quantification of the acoustic environment. Researchers will test hypotheses regarding how sounds structure communities directly by masking cues used for communication or predator/prey detection, directly via elevated perceived risk through a reduction in auditory surveillance, or indirectly by altering prey distributions.