Behavioral Ecology and Sociobiology

, Volume 64, Issue 1, pp 69–79 | Cite as

Bats aloft: variability in echolocation call structure at high altitudes

  • Erin H. GillamEmail author
  • Gary F. McCracken
  • John K. Westbrook
  • Ya-Fu Lee
  • Michael L. Jensen
  • Ben B. Balsley
Original Paper


Bats alter their echolocation in response to changes in ecological and behavioral conditions, but little is known about how they adjust call structure in response to changes in altitude. We examined altitudinal variation in the echolocation of Brazilian free-tailed bats, Tadarida brasiliensis, a species known to fly to altitudes of 3,000 m above the ground. From 50.2 h of recordings, we analyzed 113 high-quality echolocation call sequences recorded from 0 to 862 m above ground level. Bats flying near the ground used shorter, higher-frequency, broader-bandwidth calls compared to bats at higher altitudes, an effect likely due to the greater levels of echo-producing clutter (i.e., vegetation, buildings) found near the ground. When ground-level recordings are excluded, bats continue to shift towards the use of longer-duration, lower-frequency, narrower-bandwidth calls with increasing altitude. We propose that the observed high-altitude changes in call structure are a response to changing acoustic attenuation rates and/or decreasing insect densities at higher altitudes.


Echolocation Bats High altitude Signal plasticity Tadarida 



This manuscript is dedicated to Professor Donald R. Griffin, a pioneer who encouraged our work on bats aloft. We thank Y.-M. Kuo, R. Eyster, and P. Schleider for the field assistance and R. King, K. White, and the W. Gilleland family for numerous favors and logistic assistance. We also thank Dr. M. Brock Fenton and two anonymous reviewers for the comments on earlier versions of the manuscript.


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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Erin H. Gillam
    • 1
    • 4
    Email author
  • Gary F. McCracken
    • 1
  • John K. Westbrook
    • 2
  • Ya-Fu Lee
    • 1
    • 5
  • Michael L. Jensen
    • 3
  • Ben B. Balsley
    • 3
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of TennesseeKnoxvilleUSA
  2. 2.USDA-ARSCollege StationUSA
  3. 3.CIRES, 216 UCBUniversity of ColoradoBoulderUSA
  4. 4.Department of Biological SciencesNorth Dakota State UniversityFargoUSA
  5. 5.Department of Life Sciences and Institute of BiodiversityNational Cheng Kung UniversityTainanTaiwan

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