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ABSTRACT: We present synchronized time-resolved measurements of the wing kinematics and wake velocities for a medium sized bat, Cynopterus brachyotis, flying at low-medium speed in a closed-return wind tunnel. Measurements of the motion of the body and wing joints, as well
as the resultant wake velocities in the Trefftz plane are recorded at 200Hz (approximately 28–31 measurements per wing beat).
Circulation profiles are found to be quite repeatable although variations in the flight profile are visible in the wake vortex
structures. The circulation has almost constant strength over the middle half of the wing beat (defined according the vertical
motion of the wrist, beginning with the downstroke). A strong streamwise vortex is observed to be shed from the wingtip, growing
in strength during the downstroke, and persisting during much of the upstroke. At relatively low flight speeds (4.3m/s),
a closed vortex structure behind the bat is postulated.
Experiments in Fluids 04/2012; 46(5):933-943. · 1.74 Impact Factor
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ABSTRACT: To date, wake measurements using particle image velocimetry (PIV) of bats in flight have studied only three bat species, all fruit and nectar feeders. In this study, we present the first wake structure analysis for an insectivorous bat. Tadarida brasiliensis, the Brazilian free-tailed bat, is an aerial hunter that annually migrates long distances and also differs strikingly from the previously investigated species morphologically. We compare the aerodynamics of T. brasiliensis with those of other, frugivorous bats and with common swifts, Apus apus, a bird with wing morphology, kinematics and flight ecology similar to that of these bats. The comparison reveals that, for the range of speeds evaluated, the cyclical pattern of aerodynamic forces associated with a wingbeat shows more similarities between T. brasiliensis and A. apus than between T. brasiliensis and other frugivorous bats.
Journal of The Royal Society Interface 01/2012; 9(71):1120-30. · 4.40 Impact Factor
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ABSTRACT: The tiger moth Bertholdia trigona is the only animal in nature known to defend itself by jamming the sonar of its predators - bats. In this study we analyzed the three-dimensional flight paths and echolocation behavior of big brown bats (Eptesicus fuscus) attacking B. trigona in a flight room over seven consecutive nights to determine the acoustic mechanism of the sonar-jamming defense. Three mechanisms have been proposed: (1) the phantom echo hypothesis, which states that bats misinterpret moth clicks as echoes; (2) the ranging interference hypothesis, which states that moth clicks degrade the bats' precision in determining target distance; and (3) the masking hypothesis, which states that moth clicks mask the moth echoes entirely, making the moth temporarily invisible. On nights one and two of the experiment, the bats appeared startled by the clicks; however, on nights three through seven, the bats frequently missed their prey by a distance predicted by the ranging interference hypothesis (∼15-20 cm). Three-dimensional simulations show that bats did not avoid phantom targets, and the bats' ability to track clicking prey contradicts the predictions of the masking hypothesis. The moth clicks also forced the bats to reverse their stereotyped pattern of echolocation emissions during attack, even while bats continued pursuit of the moths. This likely further hinders the bats' ability to track prey. These results have implications for the evolution of sonar jamming in tiger moths, and we suggest evolutionary pathways by which sonar jamming may have evolved from other tiger moth defense mechanisms.
Journal of Experimental Biology 07/2011; 214(Pt 14):2416-25. · 3.00 Impact Factor
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ABSTRACT: Since the late 1980s, Brazilian free-tailed bats (Tadarida brasiliensis) have increasingly used bridges as roosts in the southern United States. We examined differences in blood cortisol levels, body condition, and parasite load, as measures of physiological stress in bats roosting in bridges and bats roosting in caves. We collected data during three periods, coinciding with female phases of reproduction. For all measures, bats were captured during the nightly emergence from the roost and immediately sampled. Cortisol levels were significantly higher during pregnancy and lactation and in individuals with lower body-condition scores (length of forearm to mass ratio) and significantly higher in bats roosting in caves than in those roosting in bridges. Thus, we concluded that individuals of this species that roost in bridges are not chronically stressed and seem to be unaffected by human activities present at bridges. This is a rare documented instance where a human-dominated environment does not appear to be adversely affecting the physiological health of a free-ranging animal.
Conservation Biology 12/2010; 25(2):374-81. · 4.69 Impact Factor
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IEEE 12th International Conference on Computer Vision, ICCV 2009, Kyoto, Japan, September 27 - October 4, 2009; 01/2009
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Thomas H Kunz,
Sidney A Gauthreaux, Nickolay I Hristov,
Jason W Horn,
Gareth Jones,
Elisabeth K V Kalko,
Ronald P Larkin,
Gary F McCracken,
Sharon M Swartz,
Robert B Srygley,
Robert Dudley,
John K Westbrook,
Martin Wikelski
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ABSTRACT: Aeroecology is a discipline that embraces and integrates the domains of atmospheric science, ecology, earth science, geography, computer science, computational biology, and engineering. The unifying concept that underlies this emerging discipline is its focus on the planetary boundary layer, or aerosphere, and the myriad of organisms that, in large part, depend upon this environment for their existence. The aerosphere influences both daily and seasonal movements of organisms, and its effects have both short- and long-term consequences for species that use this environment. The biotic interactions and physical conditions in the aerosphere represent important selection pressures that influence traits such as size and shape of organisms, which in turn facilitate both passive and active displacements. The aerosphere also influences the evolution of behavioral, sensory, metabolic, and respiratory functions of organisms in a myriad of ways. In contrast to organisms that depend strictly on terrestrial or aquatic existence, those that routinely use the aerosphere are almost immediately influenced by changing atmospheric conditions (e.g., winds, air density, precipitation, air temperature), sunlight, polarized light, moon light, and geomagnetic and gravitational forces. The aerosphere has direct and indirect effects on organisms, which often are more strongly influenced than those that spend significant amounts of time on land or in water. Future advances in aeroecology will be made when research conducted by biologists is more fully integrated across temporal and spatial scales in concert with advances made by atmospheric scientists and mathematical modelers. Ultimately, understanding how organisms such as arthropods, birds, and bats aloft are influenced by a dynamic aerosphere will be of importance for assessing, and maintaining ecosystem health, human health, and biodiversity.
Integrative and Comparative Biology 07/2008; 48(1):1-11. · 2.45 Impact Factor
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ABSTRACT: The night sky remains a largely unexplored frontier for biologists studying the behavior and physiology of free-ranging, nocturnal organisms. Conventional imaging tools and techniques such as night-vision scopes, infrared-reflectance cameras, flash cameras, and radar provide insufficient detail for the scale and resolution demanded by field researchers. A new tool is needed that is capable of imaging noninvasively in the dark at high-temporal and spatial resolution. Thermal infrared imaging represents the most promising such technology that is poised to revolutionize our ability to observe and document the behavior of free-ranging organisms in the dark. Herein we present several examples from our research on free-ranging bats that highlight the power and potential of thermal infrared imaging for the study of animal behavior, energetics and censusing of large colonies, among others. Using never-before-seen video footage and data, we have begun to answer questions that have puzzled biologists for decades, as well as to generate new hypotheses and insight. As we begin to appreciate the functional significance of the aerosphere as a dynamic environment that affects organisms at different spatial and temporal scales, thermal infrared imaging can be at the forefront of the effort to explore this next frontier.
Integrative and Comparative Biology 07/2008; 48(1):50-9. · 2.45 Impact Factor
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2007 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR 2007), 18-23 June 2007, Minneapolis, Minnesota, USA; 01/2007
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ABSTRACT: The night sky is the venue for an ancient arms race. Insectivorous bats with their ultrasonic sonar exert an enormous selective pressure on nocturnal insects. In response insects have evolved the ability to hear bat cries, to evade their hunting maneuvers, and some, the tiger moths (Arctiidae), to utter an ultrasonic reply. We here determine what it is that tiger moths "say" to bats. We chose four species of arctiid moths, Cycnia tenera, Euchaetes egle, Utetheisa ornatrix, and Apantesis nais, that naturally differ in their levels of unpalatability and their ability to produce sound. Moths were tethered and offered to free-flying naive big brown bats, Eptesicus fuscus. The ability of the bats to capture each species was compared to their ability to capture noctuid, geometrid, and wax moth controls over a learning period of 7 days. We repeated the experiment using the single arctiid species E. egle that through diet manipulation and simple surgery could be rendered palatable or unpalatable and sound producing or mute. We again compared the capture rates of these categories of E. egle to control moths. Using both novel learning approaches we have found that the bats only respond to the sounds of arctiids when they are paired with defensive chemistry. The sounds are in essence a warning to the bats that the moth is unpalatable-an aposematic signal.
Naturwissenschaften 05/2005; 92(4):164-9. · 2.28 Impact Factor
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Thomas H Kunz,
Sidney A. Jr. Gauthreaux, Nickolay I Hristov,
Jason W Horn,
Gareth Jones,
Elisabeth K V Kalko,
Ronald P Larkin,
Gary F McCracken,
Sharon M Swartz,
Robert B. Srygley,
Robert Dudley,
John K Westbrook,
Martin Wikelski
[show abstract]
[hide abstract]
ABSTRACT: Aeroecology is a discipline that embraces and integrates the domains of atmospheric science, ecology, earth science, geography, computer science, computational biology, and engineering. The unifying concept that underlies this emerging discipline is its focus on the planetary boundary layer, or aerosphere, and the myriad of organisms that, in large part, depend upon this environment for their existence. The aerosphere influences both daily and seasonal movements of organisms, and its effects have both short- and long-term consequences for species that use this environment. The biotic interactions and physical conditions in the aerosphere represent important selection pressures that influence traits such as size and shape of organisms, which in turn facilitate both passive and active displacements. The aerosphere also influences the evolution of behavioral, sensory, metabolic, and respiratory functions of organisms in a myriad of ways. In contrast to organisms that depend strictly on terrestrial or aquatic existence, those that routinely use the aerosphere are almost immediately influenced by changing atmospheric conditions (e.g., winds, air density, precipitation, air temperature), sunlight, polarized light, moon light, and geomagnetic and gravitational forces. The aerosphere has direct and indirect effects on organisms, which often are more strongly influenced than those that spend significant amounts of time on land or in water. Future advances in aeroecology will be made when research conducted by biologists is more fully integrated across temporal and spatial scales in concert with advances made by atmospheric scientists and mathematical modelers. Ultimately, understanding how organisms such as arthropods, birds, and bats aloft are influenced by a dynamic aerosphere will be of importance for assessing, and maintaining ecosystem health, human health, and biodiversity.
