Nondimensional aerodynamic parameters versus disk loading (eq. 3) for all autorotative descents o... more Nondimensional aerodynamic parameters versus disk loading (eq. 3) for all autorotative descents of Manifera talaris models and Agathis australis models and seeds. A, Reynolds number (Re, eq. 1). B, Advance ratio (J, eq. 2). C, Effective lift coefficient (CL,eff, eq. 7). D, Effective drag coefficient (CD,eff, eq. 6)
Synopsis Aerodynamic studies using physical models of fossil organisms can provide quantitative i... more Synopsis Aerodynamic studies using physical models of fossil organisms can provide quantitative information about how performance of defined activities, such as gliding, depends on specific morphological features. Such analyses allow us to rule out hypotheses about the function of extinct organisms that are not physically plausible and to determine if and how specific morphological features and postures affect performance. The purpose of this article is to provide a practical guide for the design of dynamically scaled physical models to study the gliding of extinct animals using examples from our research on the theropod dinosaur, †Microraptor gui, which had flight feathers on its hind limbs as well as on its forelimbs. Analysis of the aerodynamics of †M. gui can shed light on the design of gliders with large surfaces posterior to the center of mass and provide functional information to evolutionary biologists trying to unravel the origins of flight in the dinosaurian ancestors and ...
Chimney swifts (<i>Chaetura pelagica</i>) are highly manoeuvrable birds notable for r... more Chimney swifts (<i>Chaetura pelagica</i>) are highly manoeuvrable birds notable for roosting overnight in chimneys, in groups of hundreds or thousands of birds, before and during their autumn migration. At dusk, birds gather in large numbers from surrounding areas near a roost site. Thewhole flock then employs an orderly, but dynamic, circling approach pattern before rapidly entering a small aperture <i>en masse</i>. We recorded the three-dimensional trajectories of ≈1 800 individual birds during a 30 min period encompassing flock formation, circling, and landing, and used these trajectories to test several hypotheses relating to flock or group behaviour. Specifically, we investigated whether the swifts use local interaction rules based on topological distance (e.g. the <i>n</i> nearest neighbours, regardless of their distance) rather than physical distance (e.g. neighbours within <i>x</i> m, regardless of number) to guide interactions, whether the chimney entry zone is more or less cooperative than the surrounding flock, and whether the characteristic subgroup size is constant or varies with flock density. We found that the swift flock is structured around local rules based on physical distance, that subgroup size increases with density, and that there exist regions of the flock that are less cooperative than others, in particular the chimney entry zone.
Chimney swifts (Chaetura pelagica) are highly manoeuvrable birds notable for roosting overnight i... more Chimney swifts (Chaetura pelagica) are highly manoeuvrable birds notable for roosting overnight in chimneys, in groups of hundreds or thousands of birds, before and during their autumn migration. At dusk, birds gather in large numbers from surrounding areas near a roost site. The whole flock then employs an orderly, but dynamic, circling approach pattern before rapidly entering a small aperture en masse We recorded the three-dimensional trajectories of ≈1 800 individual birds during a 30 min period encompassing flock formation, circling, and landing, and used these trajectories to test several hypotheses relating to flock or group behaviour. Specifically, we investigated whether the swifts use local interaction rules based on topological distance (e.g. the n nearest neighbours, regardless of their distance) rather than physical distance (e.g. neighbours within x m, regardless of number) to guide interactions, whether the chimney entry zone is more or less cooperative than the surrou...
Ecological, behavioral and biomechanical studies often need to quantify animal movement and behav... more Ecological, behavioral and biomechanical studies often need to quantify animal movement and behavior in three dimensions. In laboratory studies, a common tool to accomplish these measurements is the use of multiple, calibrated high-speed cameras. Until very recently, the complexity, weight and cost of such cameras have made their deployment in field situations risky; furthermore, such cameras are not affordable to many researchers. Here, we show how inexpensive, consumer-grade cameras can adequately accomplish these measurements both within the laboratory and in the field. Combined with our methods and open source software, the availability of inexpensive, portable and rugged cameras will open up new areas of biological study by providing precise 3D tracking and quantification of animal and human movement to researchers in a wide variety of field and laboratory contexts.
Manifera talaris, a voltzian conifer from the late early to middle Permian (ca. 270 Ma) of Texas,... more Manifera talaris, a voltzian conifer from the late early to middle Permian (ca. 270 Ma) of Texas, is the earliest known conifer to produce winged seeds indicative of autorotating flight. In contrast to autorotating seeds and fruits of extant plants, the ones ofM. talarisare exceptional in that they have variable morphology. They bore two wings that produced a range of wing configurations, from seeds with two equal-sized wings to single-winged specimens, via various stages of underdevelopment of one of the wings. To examine the effects of various seed morphologies on aerodynamics and dispersal potential, we studied the flight performance of paper models of three morphotypes: symmetric double-winged, asymmetric double-winged, and single-winged. Using a high-speed camera we identified the mode of descent (plummeting, gliding, autorotation) and quantified descent speed, autorotation frequency, and other flight characteristics. To validate such modeling as an inferential tool, we compare...
Three-dimensional motion capture based on high-speed videography is a staple technique of compara... more Three-dimensional motion capture based on high-speed videography is a staple technique of comparative biomechanics. Historically, the necessary equipment has been cumbersome and expensive, thus largely precluding use of the technique in natural settings, by specialists in other fields (e.g. animal behavior, ecology), and in financially restricted situations. New consumer grade equipment (e.g. sports/action cameras, DSLR’s with HD video) offers far greater portability, and resolution and recording rates comparable to systems costing ten times as much. However, consumer grade equipment lacks the ability to synchronize among multiple cameras and may introduce substantial lens distortion. We have developed a workflow based on open-source Python or MATLAB modules that addresses such problems, and that automates some steps of 3D calibration and animal tracking to reduce both analysis time and reconstruction error. We present several data sets of flying animals (various species of insects ...
Nondimensional aerodynamic parameters versus disk loading (eq. 3) for all autorotative descents o... more Nondimensional aerodynamic parameters versus disk loading (eq. 3) for all autorotative descents of Manifera talaris models and Agathis australis models and seeds. A, Reynolds number (Re, eq. 1). B, Advance ratio (J, eq. 2). C, Effective lift coefficient (CL,eff, eq. 7). D, Effective drag coefficient (CD,eff, eq. 6)
Synopsis Aerodynamic studies using physical models of fossil organisms can provide quantitative i... more Synopsis Aerodynamic studies using physical models of fossil organisms can provide quantitative information about how performance of defined activities, such as gliding, depends on specific morphological features. Such analyses allow us to rule out hypotheses about the function of extinct organisms that are not physically plausible and to determine if and how specific morphological features and postures affect performance. The purpose of this article is to provide a practical guide for the design of dynamically scaled physical models to study the gliding of extinct animals using examples from our research on the theropod dinosaur, †Microraptor gui, which had flight feathers on its hind limbs as well as on its forelimbs. Analysis of the aerodynamics of †M. gui can shed light on the design of gliders with large surfaces posterior to the center of mass and provide functional information to evolutionary biologists trying to unravel the origins of flight in the dinosaurian ancestors and ...
Chimney swifts (<i>Chaetura pelagica</i>) are highly manoeuvrable birds notable for r... more Chimney swifts (<i>Chaetura pelagica</i>) are highly manoeuvrable birds notable for roosting overnight in chimneys, in groups of hundreds or thousands of birds, before and during their autumn migration. At dusk, birds gather in large numbers from surrounding areas near a roost site. Thewhole flock then employs an orderly, but dynamic, circling approach pattern before rapidly entering a small aperture <i>en masse</i>. We recorded the three-dimensional trajectories of ≈1 800 individual birds during a 30 min period encompassing flock formation, circling, and landing, and used these trajectories to test several hypotheses relating to flock or group behaviour. Specifically, we investigated whether the swifts use local interaction rules based on topological distance (e.g. the <i>n</i> nearest neighbours, regardless of their distance) rather than physical distance (e.g. neighbours within <i>x</i> m, regardless of number) to guide interactions, whether the chimney entry zone is more or less cooperative than the surrounding flock, and whether the characteristic subgroup size is constant or varies with flock density. We found that the swift flock is structured around local rules based on physical distance, that subgroup size increases with density, and that there exist regions of the flock that are less cooperative than others, in particular the chimney entry zone.
Chimney swifts (Chaetura pelagica) are highly manoeuvrable birds notable for roosting overnight i... more Chimney swifts (Chaetura pelagica) are highly manoeuvrable birds notable for roosting overnight in chimneys, in groups of hundreds or thousands of birds, before and during their autumn migration. At dusk, birds gather in large numbers from surrounding areas near a roost site. The whole flock then employs an orderly, but dynamic, circling approach pattern before rapidly entering a small aperture en masse We recorded the three-dimensional trajectories of ≈1 800 individual birds during a 30 min period encompassing flock formation, circling, and landing, and used these trajectories to test several hypotheses relating to flock or group behaviour. Specifically, we investigated whether the swifts use local interaction rules based on topological distance (e.g. the n nearest neighbours, regardless of their distance) rather than physical distance (e.g. neighbours within x m, regardless of number) to guide interactions, whether the chimney entry zone is more or less cooperative than the surrou...
Ecological, behavioral and biomechanical studies often need to quantify animal movement and behav... more Ecological, behavioral and biomechanical studies often need to quantify animal movement and behavior in three dimensions. In laboratory studies, a common tool to accomplish these measurements is the use of multiple, calibrated high-speed cameras. Until very recently, the complexity, weight and cost of such cameras have made their deployment in field situations risky; furthermore, such cameras are not affordable to many researchers. Here, we show how inexpensive, consumer-grade cameras can adequately accomplish these measurements both within the laboratory and in the field. Combined with our methods and open source software, the availability of inexpensive, portable and rugged cameras will open up new areas of biological study by providing precise 3D tracking and quantification of animal and human movement to researchers in a wide variety of field and laboratory contexts.
Manifera talaris, a voltzian conifer from the late early to middle Permian (ca. 270 Ma) of Texas,... more Manifera talaris, a voltzian conifer from the late early to middle Permian (ca. 270 Ma) of Texas, is the earliest known conifer to produce winged seeds indicative of autorotating flight. In contrast to autorotating seeds and fruits of extant plants, the ones ofM. talarisare exceptional in that they have variable morphology. They bore two wings that produced a range of wing configurations, from seeds with two equal-sized wings to single-winged specimens, via various stages of underdevelopment of one of the wings. To examine the effects of various seed morphologies on aerodynamics and dispersal potential, we studied the flight performance of paper models of three morphotypes: symmetric double-winged, asymmetric double-winged, and single-winged. Using a high-speed camera we identified the mode of descent (plummeting, gliding, autorotation) and quantified descent speed, autorotation frequency, and other flight characteristics. To validate such modeling as an inferential tool, we compare...
Three-dimensional motion capture based on high-speed videography is a staple technique of compara... more Three-dimensional motion capture based on high-speed videography is a staple technique of comparative biomechanics. Historically, the necessary equipment has been cumbersome and expensive, thus largely precluding use of the technique in natural settings, by specialists in other fields (e.g. animal behavior, ecology), and in financially restricted situations. New consumer grade equipment (e.g. sports/action cameras, DSLR’s with HD video) offers far greater portability, and resolution and recording rates comparable to systems costing ten times as much. However, consumer grade equipment lacks the ability to synchronize among multiple cameras and may introduce substantial lens distortion. We have developed a workflow based on open-source Python or MATLAB modules that addresses such problems, and that automates some steps of 3D calibration and animal tracking to reduce both analysis time and reconstruction error. We present several data sets of flying animals (various species of insects ...
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