The tiny difference between foraging and communication buzzes uttered by the Mexican free-tailed bat, Tadarida brasiliensis
Echolocating insectivorous bats consummate prey captures using a distinct vocal motor pattern commonly known as the terminal or feeding buzz, which is widely considered a fixed motor pattern executed independently of auditory feedback influences. The Mexican free-tailed bat, Tadarida brasiliensis, offers an opportunity to explore the role of sensory feedback in buzzing because they emit similar buzzes both in flight during foraging and while stationary as communication sounds. Here we compared the spectral and temporal patterns of foraging and communication buzzes to address whether or not auditory feedback may influence buzz patterns. We found that while foraging buzzes uttered in open space were composed of generic FM calls, communication buzzes were composed of an adapted CF–FM call similar to the call type used by T. brasiliensis when navigating in confined spaces. This provides the first evidence that some bats can make significant context-dependent changes in the spectral parameters of calls within their buzz. We also found that inter-pulse intervals, but not call durations, were different within the two buzz types. These observations indicate that though a common pattern generator hierarchically organizes all buzzes, T. brasiliensis retains a significant capacity to adapt the spectral and temporal patterns of elements within its buzzes.
KeywordsVocalization Communication Song Sensorimotor integration Echolocation
We thank Mr. Clint Netherland and the Texas A&M University Athletic Department for access to the bats of Kyle Field. We thank the Texas Parks and Wildlife Department for the collection permits. We thank Ms. Barbara French (Bat Conservation International, Austin TX) and Dr. George Pollak (University of Texas at Austin) for introducing us to the vocal behavior of the Mexican free-tailed bat and for many informative discussions. We also thank Bob and Joyce Rogers for permission to record bats foraging over their pond.
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