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United States Department of Agriculture

Agricultural Research Service

Title: Brazilian free-tailed bats (Tadarida brasiliensis: Molossidae, Chiroptera) at high altitude: Links to migratory insect populations)

Author
item Mccracken, Gary
item Gillam, Erin
item Westbrook, John
item Lee, Ya-fu
item Jensen, Michael
item Balsley, Ben

Submitted to: Integrative & Comparative Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2008
Publication Date: 6/4/2008
Citation: McCracken, G.F., Gillam, E.H., Westbrook, J.K., Lee, Y., Jensen, M., Balsley, B. 2008. Brazilian free-tailed bats (Tadarida brasiliensis: Molossidae, Chiroptera) at high altitude: Links to migratory insect populations. Integrative & Comparative Biology. 48:107-118.

Interpretive Summary: Knowledge of bat flight is restricted almost exclusively to altitudes that are within a few tens of meters above the ground. We report a total of 50.2 hrs of ultrasonic recordings made using radiomicrophone bat detectors suspended from free-floating helium balloons and kites. The data include a total of 22,353 ultrasonic bat calls from ground-level to 1,118 m above ground level (AGL). These calls are attributed to Brazilian free-tailed bats based on acoustic features and the large number and high-altitude aerial dispersion of these bats over the local landscape. Bat flight activity varied significantly throughout the air column and was greatest at 400 to 500 m AGL and near ground level. Feeding calls, indicating feeding on airborne insects, were most abundant near ground level and at 400 to 500 m AGL and were detected to altitudes of approximately 900 m AGL. The peak flight activity of bats at 400 to 500 m AGL is concordant with the altitude of the seasonal formation of a nocturnal low-altitude wind jet that has been identified as a major corridor for the northward dispersal of crop insect pests.

Technical Abstract: Existing information on the activity of bats in the aerosphere is restricted almost exclusively to altitudes that are within a few tens of meters above the ground. We report a total of 50.2 hrs of ultrasonic recordings made using radiomicrophone bat detectors suspended from free-floating helium balloons and from kites. The data include a total of 22,353 echolocation calls from ground-level to 1,118 m above ground level (AGL). These calls are attributed to Brazilian free-tailed bats based on acoustic features and the large numbers and high-altitude aerial dispersion of these bats over the local landscape. Bat activity varied significantly throughout the air column and was greatest at 400-500 m AGL and near ground level. Feeding buzzes, indicating feeding on aerial prey, were most abundant near ground level and at 400-500 m, and were detected to altitudes of approximately 900 m AGL. The peak activity of bats at 400-500 m AGL is concordant with the altitude of the atmospheric boundary layer and the seasonal formation of the low-elevation southerly wind jet that has been identified as a major aeroecological corridor for the nocturnal dispersal of noctuid moths and other insects.

Last Modified: 8/24/2016
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