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Debbie Beucher – An Acoustic Survey for Bats Along the Colorado River Corridor
Appropriate conservation requires an understanding of how the resource is used by an animal. Because bats are nocturnal mammals, knowledge of how they use a resource has been difficult and time-consuming to obtain. Prior to the development of ultrasonic bat detectors, a resource inventory for bats was conducted using standard mist-netting techniques at water sources. However, netting is biased towards bats easily captured over pools of water or along low flyways. In addition, the vast remoteness of much of the Colorado River Plateau, combined with the ability of bats to fly long distances over rugged terrain, has constrained our knowledge of when and how bats might use the resource. However, since the development of affordable field-robust bat detectors, we now have another tool by which to evaluate the landscape for use by bats. I will present a brief overview of bat echolocation plus information regarding two field-popular bat detectors: Anabat II (frequency division) and Pettersson D240x (time-expansion). Both detectors are designed to record the ultrasonic calls of bats for later identification in the laboratory. But because each system has known advantages and disadvantages, by combining the two methods we benefit from the advantages and reduce the disadvantages. I will discuss the techniques I used to monitor bat use of the Colorado River corridor using both detectors, providing specific examples of acoustic sampling of ultrasonic bat call conducted during a research river trip in September 2004.