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| Author |
Burns, T.E.; Clayton, H.M. |
| Title |
Comparison of the temporal kinematics of the canter pirouette and collected canter |
Type |
Journal Article |
| Year |
1997 |
Publication |
Equine Veterinary Journal. Supplement |
Abbreviated Journal |
Equine Vet J Suppl |
| Volume |
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Issue |
23 |
Pages |
58-61 |
| Keywords |
Animals; Forelimb/physiology; Gait/*physiology; Hindlimb/physiology; Horses/*physiology; Locomotion/*physiology; Movement/physiology; Time Factors; Videotape Recording; Walking/physiology |
| Abstract |
The objectives were to compare the temporal characteristics of canter pirouette strides with collected canter strides in elite dressage horses, and to determine whether the stride kinematics of the canter pirouettes fulfilled the requirements specified in the Federation Equestre Internationale Rules for Dressage Events. Eleven horses were videotaped (60 fields/s) during the individual medal competition at the 1992 Olympic Games. Temporal variables were extracted from the videotapes using standard methods. Two strides were analysed on each of the left and right leads and these were pooled to give mean values for the collected canter and the pirouettes. The pirouettes were completed in 4-9 strides, (mean of 6.4). In the collected canter strides, mean duration of the suspension was 0.013 s. There was no suspension in any of the pirouette strides, instead the stance phases of the leading forelimb and trailing hindlimb overlapped by a mean of 0.163 s. In 9 horses the trailing forelimb contacted the ground before the diagonal leading hindlimb in the collected canter, whereas in the pirouettes the leading hindlimb always made contact before the trailing forelimb (mean dissociation 0.164 s), giving the strides a distinct 4 beat rhythm. Due to increases in advanced placement between the diagonal limb pair and between the 2 forelimbs, the stride duration was longer in the pirouette (0.879 s) than the collected canter (0.629 s). It is concluded that the canter pirouette strides did not maintain the rhythm and timing of the the collected canter strides in any of the 11 horses. |
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Department of Veterinary Anatomy, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada |
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PMID:9354291 |
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Equine Behaviour @ team @ |
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3737 |
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| Author |
Clayton, H.M. |
| Title |
Classification of collected trot, passage and piaffe based on temporal variables |
Type |
Journal Article |
| Year |
1997 |
Publication |
Equine Veterinary Journal. Supplement |
Abbreviated Journal |
Equine Vet J Suppl |
| Volume |
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Issue |
23 |
Pages |
54-57 |
| Keywords |
Analysis of Variance; Animals; Discriminant Analysis; Gait/*physiology; Hindlimb/physiology; Horses/*physiology; Locomotion/*physiology; Male; Running/physiology; Time Factors; Videotape Recording; Walking/physiology |
| Abstract |
The objective was to determine whether collected trot, passage and piaffe could be distinguished as separate gaits on the basis of temporal variables. Sagittal plane, 60 Hz videotapes of 10 finalists in the dressage competitions at the 1992 Olympic Games were analysed to measure the temporal variables in absolute terms and as percentages of stride duration. Classification was based on analysis of variance, a graphical method and discriminant analysis. Stride duration was sufficient to distinguish collected trot from passage and piaffe in all horses. The analysis of variance showed that the mean values of most variables differed significantly between passage and piaffe. When hindlimb stance percentage was plotted against diagonal advanced placement percentage, some overlap was found between all 3 movements indicating that individual horses could not be classified reliably in this manner. Using hindlimb stance percentage and diagonal advanced placement percentage as input in a discriminant analysis, 80% of the cases were classified correctly, but at least one horse was misclassified in each movement. When the absolute, rather than percentage, values of the 2 variables were used as input in the discriminant analysis, 90% of the cases were correctly classified and the only misclassifications were between passage and piaffe. However, the 2 horses in which piaffe was misclassified as passage were the gold and silver medallists. In general, higher placed horses tended toward longer diagonal advanced placements, especially in collected trot and passage, and shorter hindlimb stance percentages in passage and piaffe. |
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Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada |
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PMID:9354290 |
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Equine Behaviour @ team @ |
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3738 |
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| Author |
Barrey, E.; Galloux, P. |
| Title |
Analysis of the equine jumping technique by accelerometry |
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Journal Article |
| Year |
1997 |
Publication |
Equine Veterinary Journal. Supplement |
Abbreviated Journal |
Equine Vet J Suppl |
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23 |
Pages |
45-49 |
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*Acceleration; Analysis of Variance; Animals; Forelimb/physiology; Hindlimb/physiology; Horses/*physiology; Locomotion/*physiology; Movement/physiology; Time Factors |
| Abstract |
The purpose of this study was to demonstrate the relationships between jumping technique and dorsoventral acceleration measured at the sternum. Eight saddle horses of various jumping abilities competed on a selective experimental show jumping course including 14 obstacles. An accelerometric belt fastened onto the thorax continuously measured the dorsoventral acceleration during the course. At each jump, 11 locomotor parameters (acceleration peaks, durations and stride frequency) were obtained from the dorsoventral acceleration-time curves. The type of obstacle significantly influenced the hindlimb acceleration peak at take-off and the landing acceleration peak (P<0.01). The poor jumpers exhibited a higher mean forelimb acceleration peak at take-off, a higher forelimb/hindlimb ratio between peaks of acceleration (F/H), and a lower approach stride frequency than good jumpers. Knocking over an obstacle was significantly associated with a low hindlimb acceleration peak at take-off and a high F/H ratio (P<0.01). In order to observe the continuous changes in the frequency domain of the dorsoventral acceleration during the approach and take-off phase, a Morlet's wavelet analysis was computed for each horse jumping over a series of 3 vertical obstacles. Different patterns of time-frequency images obtained by wavelet analysis were found when the horse either knocked over a vertical obstacle or cleared it. In the latter case, the image pattern showed an instantaneous increase in stride frequency at the end of the approach phase, and a marked energy content in the middle frequency range at take-off. |
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INRA Station de Genetique Quantitative et Appliquee, Groupe cheval, Jouy-en-Josas, France |
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PMID:9354288 |
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no |
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Equine Behaviour @ team @ |
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3796 |
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| Author |
Galloux, P.; Barrey, E. |
| Title |
Components of the total kinetic moment in jumping horses |
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Journal Article |
| Year |
1997 |
Publication |
Equine Veterinary Journal. Supplement |
Abbreviated Journal |
Equine Vet J Suppl |
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23 |
Pages |
41-44 |
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Algorithms; Animals; Exertion/*physiology; Female; Gravitation; Horses/*physiology; Kinetics; Locomotion/*physiology; Male; Models, Biological; Movement/*physiology; Video Recording |
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Thirty horses were filmed with a panning camera operating at 50 frames/s as they jumped over a 1.20 x 1.20 m fence. The markers of 9 joints on the horse and 7 joints on the rider were tracked in 2D with the TrackEye system. The centre of gravity and moment of inertia of each segment were calculated using a geometric algorithm and a cylindric model, respectively. The kinetic moment of each part of the horse was calculated after filtering, and resampling of data. This method showed the relative contribution of each body segment to the body overall rotation during the take-off, jump and landing phases. It was found that the trunk, hindlimbs and head-neck had the greatest influence. The coordination between the motion of the body segments allowed the horse to control its angular speed of rotation over the fence. This remained nearly constant during the airborne phase (120 +/- 5 degrees/s). During the airborne phase, the kinetic moment was constant because its value was equal to the moment of the external forces (722 +/- 125 kg x m2/s). |
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Ecole Nationale d'Equitation, Terrefort, Saumur, France |
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PMID:9354287 |
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no |
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Equine Behaviour @ team @ |
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3797 |
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| Author |
Roberts, M. |
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Book Whole |
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1997 |
Publication |
The Man Who Listens to Horses |
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Cited By (since 1996): 17; Export Date: 21 October 2008 |
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Equine Behaviour @ team @ |
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4542 |
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Shmidt Mech, L.D. |
| Title |
Wolf pack size and food acquisition |
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Journal Article |
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1997 |
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Am Nat |
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150 |
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Equine Behaviour @ team @ Shmidt Mech1997 |
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6482 |
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Mesterton-Gibbons, M.; Dugatkin, L.A. |
| Title |
Cooperation and the Prisoner's Dilemma: towards testable models of mutualism versus reciprocity |
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Journal Article |
| Year |
1997 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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54 |
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3 |
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551-557 |
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For the purpose of distinguishing between mutualism and reciprocity in nature, recent work on the evolution of cooperation has both oversimplifed and undersimplified the distinction between these two categories of cooperation. This article addresses the resulting issues of model testability, clarifies the role of time and argues that the category of `pseudo-reciprocity' is an unnecessary complication. |
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refbase @ user @ |
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480 |
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Lafleur, D.L.; Lozano, G.A.; Sclafani, M. |
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Female mate-choice copying in guppies,Poecilia reticulata: a re-evaluation |
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Journal Article |
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1997 |
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Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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54 |
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3 |
Pages |
579-586 |
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It has been argued that intraspecific mate-choice copying can be adaptive under certain conditions. Dugatkin's (1992,Am. Nat.139, 1384-1389) work with guppies,Poecilia reticulataremains the most influential experimental demonstration of this phenomenon. We replicated Dugatkin's work using several choice criteria to ensure that our results were not dependent upon any single method of judging mate choice. We also tested our findings against two null hypotheses of differing stringency. Irrespective of the choice criteria or null hypothesis used, we did not observe any relationship between female mate choice and copying. We conclude that further experimental evidence of female mate-choice copying is required before the existence of this behaviour can be affirmed. |
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484 |
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Stephens, D.W.; Anderson, J.P.; Benson, K.E. |
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On the spurious occurrence of Tit for Tat in pairs of predator-approaching fish |
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Journal Article |
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1997 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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53 |
Issue |
1 |
Pages |
113-131 |
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An experimental analysis of the movements of predator-approaching fish is presented. The experiments evaluated two competing hypotheses. (1) Predator-approaching fish play the game-theoretical strategy Tit for Tat. Alternatively, (2) the movements of predator-approaching fish superficially resemble Tit for Tat, because fish independently orient to a predator and simultaneously attempt to stay close together. Experimental subjects were mosquito fish,Gambusia affinisapproaching a green sunfish,Lepomis cyanellusTwo experiments were performed. Experiment 1 replicated results of Milinski (1987) and Dugatkin (1991), showing thatGambusiacome closer to a visible predator when a mirror is oriented parallel to their direction of travel. Experiment 2 attempted to separate the effects of common orientation and social cohesion in accounting for the frequency of Tit-for-Tat-like motions in pairs of predator-approachingGambusia. Results of experiment 2 suggest that a simple additive combination of the effects of (1) social cohesion in the absence of a visible predator and (2) orientation to a visible predator in the absence of a visible companion can account for the observed frequency of Tit-for-Tat-like motions for pairs of predator-approachingGambusia. It is concluded that predator approach in shoaling fishes is probably a simple by-product mutualism, rather than cooperation maintained by reciprocity in a Prisoner's Dilemma. |
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refbase @ user @ |
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486 |
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Reeve, H. Kern |
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Evolutionarily stable communication between kin: a general model |
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Journal Article |
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1997 |
Publication |
Proceedings of the Royal Society B: Biological Sciences |
Abbreviated Journal |
Proc. Roy. Soc. Lond. B Biol. Sci. |
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264 |
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(1384) |
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1037-1040. |
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Signalling Systems |
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At present, the most general evolutionary theory of honest communication is Grafen's model of Zahavi's 'handicap' signalling system, in which honesty of signals about the signaller's quality (e.g. mate suitability or fighting ability) is maintained by the differentially high cost of signals to signallers having lower quality. The latter model is here further generalized to include any communication between signallers and receivers that are genetically related (e.g. parents and begging offspring, cooperative or competing siblings). Signalling systems involving relatives are shown to be evolutionarily stable, despite a potential pay-off for false signalling, if the Zahavian assumption of differential signal costs holds and there are diminishing reproductive returns to the signaller as the receiver's assessed value of its attribute increases, or if, regardless of whether the Zahavian assumption holds, signallers with high values of the attribute benefit more from a given receiver assessment than signallers with low values (e.g. begging chicks that are hungrier benefit more from being fed). In stable systems of signalling among kin, it is also shown to be generally true that (i) levels of signalling and thus observed signal costs will decline as relatedness increases or as the receiver's reproductive penalty for erroneous assessment increases, and (ii) receivers will consistently, altruistically overestimate the true value of the signalled attribute. |
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refbase @ user @ |
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