title: Brazilian free-tailed bats (Tadarida brasiliensis: Molossidae, Chiroptera) at high altitude: links to migratory insect populations.
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 h of ultrasonic recordings made using radio microphonic bat detectors suspended from free-floating helium balloons and from kites. The data include a total of 22 353 echolocative calls from ground-level to 1118 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 ∼ 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.
authors.affiliation: *Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996-1610, USA; United States Department of Agriculture-Agricultural Research Service, 2771 F&B Road, College Station, Texas, 77845, USA; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.
authors.forename: Gary F
authors.initials: GF
authors.lastname: McCracken
authors.forename: Erin H
authors.initials: EH
authors.lastname: Gillam
authors.forename: John K
authors.initials: JK
authors.lastname: Westbrook
authors.forename: Ya-Fu
authors.initials: YF
authors.lastname: Lee
authors.forename: Michael L
authors.initials: ML
authors.lastname: Jensen
authors.forename: Ben B
authors.initials: BB
authors.lastname: Balsley