Publication Date

10-30-2013

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Supervisory Committee Chair

Jesse Barber

Supervisory Committee Member

James Belthoff

Supervisory Committee Member

Ian Robertson

Abstract

Anthropogenic noise is prevalent across many landscapes, posing a threat of disturbance to countless human and wildlife populations. Studies have revealed that a variety of organisms are negatively affected by an increasingly loud soundscape, including auditory predators such as bats. Bats that exhibit a gleaning hunting strategy passively listen for low frequency, prey-produced sounds. Anthropogenic noise often falls within the same spectral range as important prey cues, potentially masking these signals. I investigated the effects of two sources of anthropogenic noise, traffic and gas compressor station noise, on the foraging efficiency of the North American gleaning bat Antrozous pallidus in a laboratory experiment. Bats took significantly longer to find prey under both types of noise at multiple intensities. This demonstrates that noise pollution in general is an important consideration for managing gleaning bats and their habitats. Many bats rely on echolocation for navigating and for hunting aerial insects, and several species produce calls with low frequency components; thus, echolocating bats could also experience interference from anthropogenic noise. To test how noise affects individual bat species and assemblages of bats under field conditions, I examined bat activity levels at 50 sites in a gas field located in New Mexico where sites with loud compressor stations were matched with sites lacking a compressor. My data reveal that bats with low frequency echolocation calls, including Tadarida brasiliensis, exhibited lower activity at loud sites. It is possible that anthropogenic noise interferes with low frequency components of calls, which could be the driver behind changes in activity level for this bat assemblage. The activity levels of several bat species and assemblages did not respond to noise, suggesting that some species may be less prone to acoustic disturbance. My results indicate that noise pollution is an important anthropogenic disturbance and mitigation options should be considered for reducing its negative effects on bats.

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