Journal of Comparative Physiology A

, Volume 195, Issue 10, pp 923–934 | Cite as

Context-dependent effects of noise on echolocation pulse characteristics in free-tailed bats

  • Jedediah Tressler
  • Michael S. Smotherman
Original Paper


Background noise evokes a similar suite of adaptations in the acoustic structure of communication calls across a diverse range of vertebrates. Echolocating bats may have evolved specialized vocal strategies for echolocating in noise, but also seem to exhibit generic vertebrate responses such as the ubiquitous Lombard response. We wondered how bats balance generic and echolocation-specific vocal responses to noise. To address this question, we first characterized the vocal responses of flying free-tailed bats (Tadarida brasiliensis) to broadband noises varying in amplitude. Secondly, we measured the bats’ responses to band-limited noises that varied in the extent of overlap with their echolocation pulse bandwidth. We hypothesized that the bats’ generic responses to noise would be graded proportionally with noise amplitude, total bandwidth and frequency content, and consequently that more selective responses to band-limited noise such as the jamming avoidance response could be explained by a linear decomposition of the response to broadband noise. Instead, the results showed that both the nature and the magnitude of the vocal responses varied with the acoustic structure of the outgoing pulse as well as non-linearly with noise parameters. We conclude that free-tailed bats utilize separate generic and specialized vocal responses to noise in a context-dependent fashion.


Echolocation Vocalization Noise Lombard response Vocal plasticity Jamming avoidance response 



Jamming avoidance response






Start frequency of the pulse


End frequency of the pulse


Frequency of the part of the pulse with greatest amplitude



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 Kristin Denton for her most excellent animal care and help with running the experiments, Dr. Kirsten Bohn for help with statistics, and Christine Schwartz, Jenna Jarvis, Dr. Bohn, and Dr. George Pollak for many informative discussions. All husbandry and experimental procedures were in accordance with NIH guidelines for experiments involving vertebrate animals and were approved by the local IACUC. The research was supported by Texas A&M University and NIH Grant DC007962 to M.S. Smotherman


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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  1. 1.Department of BiologyTexas A&M UniversityCollege StationUSA

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