| Records |
| Author |
Johnson, D.D.P.; Stopka, P.; Knights, S. |
| Title |
Sociology: The puzzle of human cooperation |
Type |
Journal Article |
| Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
421 |
Issue |
6926 |
Pages |
911-2; discussion 912 |
| Keywords |
Altruism; *Cooperative Behavior; Evolution; Humans; *Models, Biological; Punishment; Reward; Risk |
| Abstract |
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| Address |
Olin Institute for Strategic Studies, Harvard University, Cambridge, Massachusetts 02138, USA. dominic@post.harvard.edu |
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English |
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0028-0836 |
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| Notes |
PMID:12606989 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
467 |
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| Author |
Wilson, A.M.; McGuigan, M.P.; Su, A.; van Den Bogert, A.J. |
| Title |
Horses damp the spring in their step |
Type |
Journal Article |
| Year |
2001 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
414 |
Issue |
6866 |
Pages |
895-899 |
| Keywords |
Animals; Biomechanics; Elasticity; Forelimb; Gait; Horses/anatomy & histology/*physiology; Leg Bones/*physiology; Locomotion; Models, Biological; Muscle Fibers/physiology; Muscle, Skeletal/anatomy & histology/*physiology; Tendons/anatomy & histology/*physiology; Vibration |
| Abstract |
The muscular work of galloping in horses is halved by storing and returning elastic strain energy in spring-like muscle-tendon units.These make the legs act like a child's pogo stick that is tuned to stretch and recoil at 2.5 strides per second. This mechanism is optimized by unique musculoskeletal adaptations: the digital flexor muscles have extremely short fibres and significant passive properties, whereas the tendons are very long and span several joints. Length change occurs by a stretching of the spring-like digital flexor tendons rather than through energetically expensive length changes in the muscle. Despite being apparently redundant for such a mechanism, the muscle fibres in the digital flexors are well developed. Here we show that the mechanical arrangement of the elastic leg permits it to vibrate at a higher frequency of 30-40 Hz that could cause fatigue damage to tendon and bone. Furthermore, we show that the digital flexor muscles have minimal ability to contribute to or regulate significantly the 2.5-Hz cycle of movement, but are ideally arranged to damp these high-frequency oscillations in the limb. |
| Address |
Department of Veterinary Basic Sciences, The Royal Veterinary College, Hatfield, Herts AL9 7TA, UK. awilson@rvc.ac.uk |
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English |
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| ISSN |
0028-0836 |
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| Notes |
PMID:11780059 |
Approved |
no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
2300 |
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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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0028-0836 |
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Conference |
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| Notes |
PMID:12520299 |
Approved |
no |
| Call Number |
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 |
Approved |
no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
5138 |
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| Author |
Scheffer, M.; van Nes, E.H. |
| Title |
Self-organized similarity, the evolutionary emergence of groups of similar species |
Type |
Journal Article |
| Year |
2006 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
| Volume |
103 |
Issue |
16 |
Pages |
6230-6235 |
| Keywords |
Animals; *Competitive Behavior; *Ecosystem; *Evolution; *Models, Biological |
| Abstract |
Ecologists have long been puzzled by the fact that there are so many similar species in nature. Here we show that self-organized clusters of look-a-likes may emerge spontaneously from coevolution of competitors. The explanation is that there are two alternative ways to survive together: being sufficiently different or being sufficiently similar. Using a model based on classical competition theory, we demonstrate a tendency for evolutionary emergence of regularly spaced lumps of similar species along a niche axis. Indeed, such lumpy patterns are commonly observed in size distributions of organisms ranging from algae, zooplankton, and beetles to birds and mammals, and could not be well explained by earlier theory. Our results suggest that these patterns may represent self-constructed niches emerging from competitive interactions. A corollary of our findings is that, whereas in species-poor communities sympatric speciation and invasion of open niches is possible, species-saturated communities may be characterized by convergent evolution and invasion by look-a-likes. |
| Address |
Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 8080, 6700 DD, Wageningen, The Netherlands. marten.scheffer@wur.nl |
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English |
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Edition |
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| ISSN |
0027-8424 |
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| Notes |
PMID:16585519 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
510 |
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| Author |
Mettke-Hofmann, C.; Gwinner, E. |
| Title |
Long-term memory for a life on the move |
Type |
Journal Article |
| Year |
2003 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
| Volume |
100 |
Issue |
10 |
Pages |
5863-5866 |
| Keywords |
Animals; Germany; Israel; Memory/*physiology; Models, Biological; Periodicity; Songbirds/*physiology |
| Abstract |
Evidence is accumulating that cognitive abilities are shaped by the specific ecological conditions to which animals are exposed. Long-distance migratory birds may provide a striking example of this. Field observations have shown that, at least in some species, a substantial proportion of individuals return to the same breeding, wintering, and stopover sites in successive years. This observation suggests that migrants have evolved special cognitive abilities that enable them to accomplish these feats. Here we show that memory of a particular feeding site persisted for at least 12 months in a long-distance migrant, whereas a closely related nonmigrant could remember such a site for only 2 weeks. Thus, it seems that the migratory lifestyle has influenced the learning and memorizing capacities of migratory birds. These results build a bridge between field observations suggesting special memorization feats of migratory birds and previous neuroanatomical results from the same two species indicating an increase in relative hippocampal size from the first to the second year of life in the migrant but not in the nonmigrant. |
| Address |
Max Planck Research Centre for Ornithology, Department of Biological Rhythms and Behaviour, Von-der-Tann-Strasse 7, 82346 Andechs, Germany. mettke-hofmann@erl.ornithol.mpg.de |
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English |
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Edition |
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| ISSN |
0027-8424 |
ISBN |
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Conference |
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| Notes |
PMID:12719527 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
511 |
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| Author |
Bergstrom, C.T.; Lachmann, M. |
| Title |
Signaling among relatives. III. Talk is cheap |
Type |
Journal Article |
| Year |
1998 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
| Volume |
95 |
Issue |
9 |
Pages |
5100-5105 |
| Keywords |
Animal Communication; Animals; Costs and Cost Analysis; *Evolution; Interpersonal Relations; Models, Biological |
| Abstract |
The Sir Philip Sidney game has been used by numerous authors to show how signal cost can facilitate honest signaling among relatives. Here, we demonstrate that, in this game, honest cost-free signals are possible as well, under very general conditions. Moreover, these cost-free signals are better for all participants than the previously explored alternatives. Recent empirical evidence suggests that begging is energetically inexpensive for nestling birds; this finding led some researchers to question the applicability of the costly signaling framework to nestling begging. Our results show that cost-free or inexpensive signals, as observed empirically, fall within the framework of signaling theory. |
| Address |
Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. carl@charles.stanford.edu |
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English |
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0027-8424 |
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| Notes |
PMID:9560235 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
561 |
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| Author |
Kiltie, R.A.; Fan, J.; Laine, A.F. |
| Title |
A wavelet-based metric for visual texture discrimination with applications in evolutionary ecology |
Type |
Journal Article |
| Year |
1995 |
Publication |
Mathematical Biosciences |
Abbreviated Journal |
Math Biosci |
| Volume |
126 |
Issue |
1 |
Pages |
21-39 |
| Keywords |
Animals; Carnivora; *Ecology; Equidae; *Evolution; Humans; Mathematics; Models, Biological; Moths; *Pattern Recognition, Visual; Pigmentation |
| Abstract |
Much work on natural and sexual selection is concerned with the conspicuousness of visual patterns (textures) on animal and plant surfaces. Previous attempts by evolutionary biologists to quantify apparency of such textures have involved subjective estimates of conspicuousness or statistical analyses based on transect samples. We present a method based on wavelet analysis that avoids subjectivity and that uses more of the information in image textures than transects do. Like the human visual system for texture discrimination, and probably like that of other vertebrates, this method is based on localized analysis of orientation and frequency components of the patterns composing visual textures. As examples of the metric's utility, we present analyses of crypsis for tigers, zebras, and peppered moth morphs. |
| Address |
Department of Zoology, University of Florida, Gainesville |
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English |
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0025-5564 |
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| Notes |
PMID:7696817 |
Approved |
no |
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Equine Behaviour @ team @ |
Serial |
2660 |
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| Author |
Viscido, S.V.; Miller, M.; Wethey, D.S. |
| Title |
The dilemma of the selfish herd: the search for a realistic movement rule |
Type |
Journal Article |
| Year |
2002 |
Publication |
Journal of theoretical biology |
Abbreviated Journal |
J. Theor. Biol. |
| Volume |
217 |
Issue |
2 |
Pages |
183-194 |
| Keywords |
Animals; *Behavior, Animal; *Mass Behavior; Models, Biological; *Motor Activity; Predatory Behavior |
| Abstract |
The selfish herd hypothesis predicts that aggregations form because individuals move toward one another to minimize their own predation risk. The “dilemma of the selfish herd” is that movement rules that are easy for individuals to follow, fail to produce true aggregations, while rules that produce aggregations require individual behavior so complex that one may doubt most animals can follow them. If natural selection at the individual level is responsible for herding behavior, a solution to the dilemma must exist. Using computer simulations, we examined four different movement rules. Relative predation risk was different for all four movement rules (p<0.05). We defined three criteria for measuring the quality of a movement rule. A good movement rule should (a) be statistically likely to benefit an individual that follows it, (b) be something we can imagine most animals are capable of following, and (c) result in a centrally compact flock. The local crowded horizon rule, which allowed individuals to take the positions of many flock-mates into account, but decreased the influence of flock-mates with distance, best satisfied these criteria. The local crowded horizon rule was very sensitive to the animal's perceptive ability. Therefore, the animal's ability to detect its neighbors is an important factor in the dynamics of group formation. |
| Address |
Department of Biological Sciences, University of South Carolina, Columbia, SC, 29208, USA. viscido@u.washington.edu |
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English |
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Edition |
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0022-5193 |
ISBN |
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Conference |
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| Notes |
PMID:12202112 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
554 |
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| Author |
Viscido, S.V.; Miller, M.; Wethey, D.S. |
| Title |
The response of a selfish herd to an attack from outside the group perimeter |
Type |
Journal Article |
| Year |
2001 |
Publication |
Journal of theoretical biology |
Abbreviated Journal |
J. Theor. Biol. |
| Volume |
208 |
Issue |
3 |
Pages |
315-328 |
| Keywords |
Animals; *Behavior, Animal; *Computer Simulation; Models, Biological; *Movement; Predatory Behavior |
| Abstract |
According to the selfish herd hypothesis, animals can decrease predation risk by moving toward one another if the predator can appear anywhere and will attack the nearest target. Previous studies have shown that aggregations can form using simple movement rules designed to decrease each animal's Domain of Danger. However, if the predator attacks from outside the group's perimeter, these simple movement rules might not lead to aggregation. To test whether simple selfish movement rules would decrease predation risk for those situations when the predator attacks from outside the flock perimeter, we constructed a computer model that allowed flocks of 75 simulated fiddler crabs to react to one another, and to a predator attacking from 7 m away. We attacked simulated crab flocks with predators of different sizes and attack speeds, and computed relative predation risk after 120 time steps. Final trajectories showed flight toward the center of the flock, but curving away from the predator. Path curvature depended on the predator's size and approach speed. The average crab experienced a greater decrease in predation risk when the predator was small or slow moving. Regardless of the predator's size and speed, however, predation risk always decreased as long as crabs took their flock-mates into account. We conclude that, even when flight away from an external predator occurs, the selfish avoidance of danger can lead to aggregation. |
| Address |
Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, U.S.A. viscido@u.washington.edu |
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English |
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0022-5193 |
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| Notes |
PMID:11207093 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
555 |
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