| Records |
| Author |
Scheibe, K.M.; Streich, W.J. |
| Title |
Annual Rhythm of Body Weight in Przewalski Horses (Equus ferus przewalskii) |
Type |
Journal Article |
| Year |
2003 |
Publication |
Biological Rhythm Research |
Abbreviated Journal |
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| Volume |
34 |
Issue |
4 |
Pages |
383-395 |
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| Abstract |
The live-weight of female Przewalski horses in a semi-natural reserve has been recorded continuously over 6 years by means of an automatic weighing machine and automatic identification. Data were tested for cyclic as well as for linear trend effects and a mathematical model was developed. A clear annual rhythm of live-weight with the maximum in October was demonstrated. During the first 2 years of recording, the level of the annual rhythm was constant but, thereafter, different individual trends were found. Those individuals showing a steeply rising trend suffered from laminitis after three annual cycles. The periods of rising body weight corresponded to unusual mild winters. Animals newly introduced into the reserve from zoos showed a rise in their body weight in an adaptation phase. Furthermore, there was evidence for a phase adjustment of the annual rhythm. The results are discussed against a background of the theory of annual rhythms, and can be used as a basis for seasonal variations of feeding in zoos and for a re-evaluation of recommendations for population density in similar reserves. For reintroductions as well as for a transfer from zoos to semi-natural reserves, a longer adaptation phase is recommended. |
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| Publisher |
Taylor & Francis |
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| ISSN |
0929-1016 |
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| Call Number |
Equine Behaviour @ team @ |
Serial |
4991 |
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| Author |
Rüegg J. C |
| Title |
Psychosomatik, Psychotherapie und Gehirn |
Type |
Book Whole |
| Year |
2003 |
Publication |
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Schattauer Verlag |
Place of Publication |
Stuttgart |
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ISBN |
978-3794521500 |
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no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
5016 |
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| Author |
Wallner, B.; Brem, G.; Muller, M.; Achmann, R. |
| Title |
Fixed nucleotide differences on the Y chromosome indicate clear divergence between Equus przewalskii and Equus caballus |
Type |
Journal Article |
| Year |
2003 |
Publication |
Animal Genetics |
Abbreviated Journal |
Anim Genet |
| Volume |
34 |
Issue |
6 |
Pages |
453-456 |
| Keywords |
Animals; Base Sequence; DNA, Mitochondrial/genetics; Genetic Variation/*genetics; Horses/classification/*genetics; Male; Molecular Sequence Data; Phylogeny; Probability; Species Specificity; Y Chromosome/*genetics |
| Abstract |
The phylogenetic relationship between Equus przewalskii and E. caballus is often a matter of debate. Although these taxa have different chromosome numbers, they do not form monophyletic clades in a phylogenetic tree based on mtDNA sequences. Here we report sequence variation from five newly identified Y chromosome regions of the horse. Two fixed nucleotide differences on the Y chromosome clearly display Przewalski's horse and domestic horse as sister taxa. At both positions the Przewalski's horse haplotype shows the ancestral state, in common with the members of the zebra/ass lineage. We discuss the factors that may have led to the differences in mtDNA and Y-chromosomal observations. |
| Address |
Institut fur Tierzucht und Genetik, Veterinarmedizinische Universitat Wien, Veterinarplatz, Wien, Austria. wallner@i122server.vu-wien.ac.at |
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English |
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| ISSN |
0268-9146 |
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| Notes |
PMID:14687077 |
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no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
5038 |
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| Author |
Bowling, A.T.; Zimmermann, W.; Ryder, O.; Penado, C.; Peto, S.; Chemnick, L.; Yasinetskaya, N.; Zharkikh, T. |
| Title |
Genetic variation in Przewalski’s horses, with special focus on the last wild caught mare, 231 Orlitza III |
Type |
Journal Article |
| Year |
2003 |
Publication |
Cytogenetic and Genome Research |
Abbreviated Journal |
Cytogenet Genome Res |
| Volume |
102 |
Issue |
1-4 |
Pages |
226-234 |
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| ISSN |
1424-8581 |
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no |
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Equine Behaviour @ team @ |
Serial |
5045 |
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| Author |
Van Doorn G.S.; Hengeveld G.M.; Weissing F.J. |
| Title |
The Evolution of Social Dominance I: Two-player Models |
Type |
Journal Article |
| Year |
2003 |
Publication |
Behavior |
Abbreviated Journal |
Behavior |
| Volume |
140 |
Issue |
10 |
Pages |
1305-1332 |
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| Abstract |
A difference in dominance rank is an often-used cue to resolve conflicts between two animals without escalated fights. At the group level, adherence to a dominance convention efficiently reduces the costs associated with conflicts, but from an individual's point of view, it is difficult to explain why a low ranking individual should accept its subordinate status. This is especially true if, as suggested by several authors, dominance not necessarily reflects differences in fighting ability but rather results from arbitrary historical asymmetries. According to this idea, rank differentiation emerges from behavioural strategies, referred to as winner and loser effects, in which winners of previous conflicts are more likely to win the current conflict, whereas the losers of previous conflicts are less likely to do so. In order to investigate whether dominance, based on such winner and loser effects, can be evolutionarily stable, we analyse a game theoretical model. The model focuses on an extreme case in which there are no differences in fighting ability between individuals at all. The only asymmetries that may arise between individuals are generated by the outcome of previous conflicts. By means of numerical analysis, we find alternative evolutionarily stable strategies, which all utilize these asymmetries for conventional conflict resolution. One class of these strategies is based on winner and loser effects, thus generating evolutionarily stable dominance relations even in the absence of differences in resource holding potential. |
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no |
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Equine Behaviour @ team @ |
Serial |
5105 |
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| Author |
Van Doorn G.S.; Hengeveld G.M.; Weissing F.J. |
| Title |
The Evolution of Social Dominance II: Multi-Player Models |
Type |
Journal Article |
| Year |
2003 |
Publication |
Behavior |
Abbreviated Journal |
Behavior |
| Volume |
140 |
Issue |
10 |
Pages |
1333-1358 |
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| Abstract |
The social hierarchies observed in natural systems often show a high degree of transitivity. Transitive hierarchies do not only require rank differentiation within pairs of individuals but also a higher level ordering of relations within the group. Several authors have suggested that the formation of linear hierarchies at the group level is an emergent property of individual behavioural rules, referred to as winner and loser effects. Winner and loser effects occur if winners of previous conflicts are more likely to escalate the current conflict, whereas the losers of previous conflicts are less likely to do so. According to this idea, an individual's position in a hierarchy may not necessarily reflect its fighting ability, but may rather result from arbitrary historical asymmetries, in particular the history of victories and defeats. However, if this is the case, it is difficult to explain from an evolutionary perspective why a low ranking individual should accept its subordinate status. Here we present a game theoretical model to investigate whether winner and loser effects giving rise to transitive hierarchies can evolve and under which conditions they are evolutionarily stable. The main version of the model focuses on an extreme case in which there are no intrinsic differences in fighting ability between individuals. The only asymmetries that may arise between individuals are generated by the outcome of previous conflicts. We show that, at evolutionary equilibrium, these asymmetries can be utilized for conventional conflict resolution. Several evolutionarily stable strategies are based on winner and loser effects and these strategies give rise to transitive hierarchies. |
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no |
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Equine Behaviour @ team @ |
Serial |
5106 |
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| Author |
Conradt, L.; Roper, T.J. |
| Title |
Group decision-making in animals |
Type |
Journal Article |
| Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
421 |
Issue |
6919 |
Pages |
155-158 |
| Keywords |
Animals; Behavior, Animal/*physiology; *Decision Making; Democracy; Group Processes; *Models, Biological; Population Density; Social Behavior |
| Abstract |
Groups of animals often need to make communal decisions, for example about which activities to perform, when to perform them and which direction to travel in; however, little is known about how they do so. Here, we model the fitness consequences of two possible decision-making mechanisms: 'despotism' and 'democracy'. We show that under most conditions, the costs to subordinate group members, and to the group as a whole, are considerably higher for despotic than for democratic decisions. Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large. Democratic decisions are more beneficial primarily because they tend to produce less extreme decisions, rather than because each individual has an influence on the decision per se. Our model suggests that democracy should be widespread and makes quantitative, testable predictions about group decision-making in non-humans. |
| Address |
School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK. l.conradt@sussex.ac.uk |
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English |
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| ISSN |
0028-0836 |
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| Notes |
PMID:12520299 |
Approved |
no |
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Equine Behaviour @ team @ |
Serial |
5136 |
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| Author |
Rands, S.A.; Cowlishaw, G.; Pettifor, R.A.; Rowcliffe, J.M.; Johnstone, R.A. |
| Title |
Spontaneous emergence of leaders and followers in foraging pairs |
Type |
Journal Article |
| Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
423 |
Issue |
6938 |
Pages |
432-434 |
| Keywords |
Animals; *Energy Metabolism; Food; *Food Chain; *Models, Biological; Motor Activity; *Social Behavior; Time Factors |
| Abstract |
Animals that forage socially often stand to gain from coordination of their behaviour. Yet it is not known how group members reach a consensus on the timing of foraging bouts. Here we demonstrate a simple process by which this may occur. We develop a state-dependent, dynamic game model of foraging by a pair of animals, in which each individual chooses between resting or foraging during a series of consecutive periods, so as to maximize its own individual chances of survival. We find that, if there is an advantage to foraging together, the equilibrium behaviour of both individuals becomes highly synchronized. As a result of this synchronization, differences in the energetic reserves of the two players spontaneously develop, leading them to adopt different behavioural roles. The individual with lower reserves emerges as the 'pace-maker' who determines when the pair should forage, providing a straightforward resolution to the problem of group coordination. Moreover, the strategy that gives rise to this behaviour can be implemented by a simple 'rule of thumb' that requires no detailed knowledge of the state of other individuals. |
| Address |
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. s.rands@zoo.cam.ac.uk |
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English |
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0028-0836 |
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| Notes |
PMID:12761547 |
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no |
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Equine Behaviour @ team @ |
Serial |
5138 |
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| Author |
Camazine, S.; Deneubourg, J.L.; Franks, N.R.; Sneyd, J.; Theraula, G.; Bonabeau, E. |
| Title |
Self-Organization in Biological Systems |
Type |
Book Whole |
| Year |
2003 |
Publication |
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Issue |
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Princeton University Press |
Place of Publication |
Princeton |
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ISBN |
978-0691116242 |
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no |
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Equine Behaviour @ team @ |
Serial |
5143 |
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| Author |
Couzin, I.D.; Krause, J. |
| Title |
Self-Organization and Collective Behavior in Vertebrates |
Type |
Book Chapter |
| Year |
2003 |
Publication |
Advances in the Study of Behavior |
Abbreviated Journal |
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| Volume |
32 |
Issue |
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Pages |
1-75 |
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Academic Press |
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Editor |
Peter J. B. Slater, J.S.R., Charles T. Snowdon and Timothy J. Roper |
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ISBN |
0065-3454 |
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Approved |
no |
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Equine Behaviour @ team @ |
Serial |
5144 |
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