| Records |
| Author |
Cameron, E.Z.; du Toit, J.T. |
| Title |
Winning by a neck: tall giraffes avoid competing with shorter browsers |
Type |
Journal Article |
| Year |
2007 |
Publication |
The American naturalist |
Abbreviated Journal  |
Am Nat |
| Volume |
169 |
Issue |
1 |
Pages |
130-135 |
| Keywords |
Acacia/growth & development; Animals; Feeding Behavior/*physiology; Neck/*anatomy & histology; Plant Leaves/growth & development; Ruminants/*anatomy & histology/*physiology; South Africa |
| Abstract |
With their vertically elongated body form, giraffes generally feed above the level of other browsers within the savanna browsing guild, despite having access to foliage at lower levels. They ingest more leaf mass per bite when foraging high in the tree, perhaps because smaller, more selective browsers deplete shoots at lower levels or because trees differentially allocate resources to promote shoot growth in the upper canopy. We erected exclosures around individual Acacia nigrescens trees in the greater Kruger ecosystem, South Africa. After a complete growing season, we found no differences in leaf biomass per shoot across height zones in excluded trees but significant differences in control trees. We conclude that giraffes preferentially browse at high levels in the canopy to avoid competition with smaller browsers. Our findings are analogous with those from studies of grazing guilds and demonstrate that resource partitioning can be driven by competition when smaller foragers displace larger foragers from shared resources. This provides the first experimental support for the classic evolutionary hypothesis that vertical elongation of the giraffe body is an outcome of competition within the browsing ungulate guild. |
| Address |
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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English |
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| ISSN |
1537-5323 |
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| Notes |
PMID:17206591 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
410 |
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| Author |
Uehara, T.; Yokomizo, H.; Iwasa, Y. |
| Title |
Mate-choice copying as Bayesian decision making |
Type |
Journal Article |
| Year |
2005 |
Publication |
The American naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
165 |
Issue |
3 |
Pages |
403-410 |
| Keywords |
Animals; *Bayes Theorem; *Choice Behavior; Female; Male; *Models, Biological; *Sexual Behavior, Animal |
| Abstract |
Mate-choice copying by females has been reported in fishes (e.g., guppies) and lekking birds. Presumably, females assess males' quality using both information from direct observation of males and information acquired by observing other females' choices. Here, we study mathematically the conditions under which mate-choice copying is advantageous on the basis of Bayesian decision theory. A female may observe the mate choice of another female, called the model female, who has performed an optimal choice based on her own judgment. The conditions required for the focal female to choose the same mate as that chosen by the model female should depend on the male's appearance to her, the reliability of her own judgment of male quality, and the reliability of the model females. When three or more females are involved, the optimal mate choice critically depends on whether multiple model females make decisions independently or they themselves copy the choices of others. If two equally reliable females choose different males, the choice of the second female, made knowing the choice of the first, should have a stronger effect on the choice of the third (focal) female. This “last-choice precedence” should be tested experimentally. |
| Address |
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan. uehara@bio-math.biology.kyushu-u.ac.jp |
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English |
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1537-5323 |
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| Notes |
PMID:15729669 |
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no |
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Serial |
1821 |
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| Author |
Dubois, F.; Giraldeau, L.-A.; Hamilton, I.M.; Grant, J.W.A.; Lefebvre, L. |
| Title |
Distraction sneakers decrease the expected level of aggression within groups: a game-theoretic model |
Type |
Journal Article |
| Year |
2004 |
Publication |
The American Naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
164 |
Issue |
2 |
Pages |
E32-45 |
| Keywords |
*Aggression; Animals; Behavior, Animal/*physiology; Columbidae/*physiology; Competitive Behavior; Cooperative Behavior; *Game Theory; Hawks/*physiology; Models, Biological |
| Abstract |
Hawk-dove games have been extensively used to predict the conditions under which group-living animals should defend their resources against potential usurpers. Typically, game-theoretic models on aggression consider that resource defense may entail energetic and injury costs. However, intruders may also take advantage of owners who are busy fighting to sneak access to unguarded resources, imposing thereby an additional cost on the use of the escalated hawk strategy. In this article we modify the two-strategy hawk-dove game into a three-strategy hawk-dove-sneaker game that incorporates a distraction-sneaking tactic, allowing us to explore its consequences on the expected level of aggression within groups. Our model predicts a lower proportion of hawks and hence lower frequencies of aggressive interactions within groups than do previous two-strategy hawk-dove games. The extent to which distraction sneakers decrease the frequency of aggression within groups, however, depends on whether they search only for opportunities to join resources uncovered by other group members or for both unchallenged resources and opportunities to usurp. |
| Address |
Departement des Sciences Biologiques, Universite du Quebec a Montreal, Case postale 8888 Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada. frede_dubois@yahoo.fr |
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English |
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1537-5323 |
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Conference |
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| Notes |
PMID:15278850 |
Approved |
no |
| Call Number |
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Serial |
2130 |
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| Author |
Dubois, F.; Giraldeau, L.-A. |
| Title |
The forager's dilemma: food sharing and food defense as risk-sensitive foraging options |
Type |
Journal Article |
| Year |
2003 |
Publication |
The American Naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
162 |
Issue |
6 |
Pages |
768-779 |
| Keywords |
Animals; Competitive Behavior/*physiology; *Environment; Feeding Behavior/*physiology; *Game Theory; *Models, Biological; Population Density; Population Dynamics |
| Abstract |
Although many variants of the hawk-dove game predict the frequency at which group foraging animals should compete aggressively, none of them can explain why a large number of group foraging animals share food clumps without any overt aggression. One reason for this shortcoming is that hawk-dove games typically consider only a single contest, while most group foraging situations involve opponents that interact repeatedly over discovered food clumps. The present iterated hawk-dove game predicts that in situations that are analogous to a prisoner's dilemma, animals should share the resources without aggression, provided that the number of simultaneously available food clumps is sufficiently large and the number of competitors is relatively small. However, given that the expected gain of an aggressive animal is more variable than the gain expected by nonaggressive individuals, the predicted effect of the number of food items in a clump-clump richness-depends on whether only the mean or both the mean and variability associated with payoffs are considered. More precisely, the deterministic game predicts that aggression should increase with clump richness, whereas the stochastic risk-sensitive game predicts that the frequency of encounters resulting in aggression should peak at intermediate clump richnesses or decrease with increasing clump richness if animals show sensitivity to the variance or coefficient of variation, respectively. |
| Address |
Departement des Sciences Biologiques, Universite du Quebec a Montreal, Case postale 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada. fdubois@u-bourgogne.fr |
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English |
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Edition |
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| ISSN |
0003-0147 |
ISBN |
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Conference |
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| Notes |
PMID:14737714 |
Approved |
no |
| Call Number |
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Serial |
2132 |
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| Author |
Conradt, L.; Krause, J.; Couzin, I. D.; Roper, T. J. |
| Title |
“Leading According to Need” in Self-Organizing Groups |
Type |
Journal Article |
| Year |
2009 |
Publication |
The American Naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
173 |
Issue |
3 |
Pages |
304-312 |
| Keywords |
behavioral synchrony, collective group decisions, democracy and egalitarianism in animals, public goods experiments, sexual segregation, social choice theory |
| Abstract |
Self‐organizing‐system approaches have shed significant light on the mechanisms underlying synchronized movements by large groups of animals, such as shoals of fish, flocks of birds, or herds of ungulates. However, these approaches rarely consider conflicts of interest between group members, although there is reason to suppose that such conflicts are commonplace. Here, we demonstrate that, where conflicts exist, individual members of self‐organizing groups can, in principle, increase their influence on group movement destination by strategically changing simple behavioral parameters (namely, movement speed, assertiveness, and social attraction range). However, they do so at the expense of an increased risk of group fragmentation and a decrease in movement efficiency. We argue that the resulting trade‐offs faced by each group member render it likely that group movements are led by those members for which reaching a particular destination is most crucial or group cohesion is least important. We term this phenomenon leading according to “need” or “social indifference,” respectively. Both kinds of leading can occur in the absence of knowledge of or communication about the needs of other group members and without the assumption of altruistic cooperation. We discuss our findings in the light of observations on fish and other vertebrates. |
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no |
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Equine Behaviour @ team @ |
Serial |
5121 |
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| Author |
Nettle, D. |
| Title |
The evolution of personality variation in humans and other animals |
Type |
Journal Article |
| Year |
2006 |
Publication |
The American Psychologist |
Abbreviated Journal |
Am Psychol |
| Volume |
61 |
Issue |
6 |
Pages |
622-631 |
| Keywords |
Animals; Birds; *Evolution; Female; Fishes; Humans; Insects; Male; Personality/*genetics/*physiology |
| Abstract |
A comprehensive evolutionary framework for understanding the maintenance of heritable behavioral variation in humans is yet to be developed. Some evolutionary psychologists have argued that heritable variation will not be found in important, fitness-relevant characteristics because of the winnowing effect of natural selection. This article propounds the opposite view. Heritable variation is ubiquitous in all species, and there are a number of frameworks for understanding its persistence. The author argues that each of the Big Five dimensions of human personality can be seen as the result of a trade-off between different fitness costs and benefits. As there is no unconditionally optimal value of these trade-offs, it is to be expected that genetic diversity will be retained in the population. |
| Address |
University of Newcastle, Newcastle, United Kingdom. daniel.nettle@ncl.ac.uk |
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English |
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0003-066X |
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| Notes |
PMID:16953749 |
Approved |
no |
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Equine Behaviour @ team @ |
Serial |
4105 |
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| Author |
Neuringer, A. |
| Title |
Reinforced variability in animals and people: implications for adaptive action |
Type |
Journal Article |
| Year |
2004 |
Publication |
The American Psychologist |
Abbreviated Journal |
Am Psychol |
| Volume |
59 |
Issue |
9 |
Pages |
891-906 |
| Keywords |
Animals; Behavior, Animal; *Choice Behavior; Conditioning, Operant; Creativeness; Discrimination (Psychology); Humans; Memory; Problem Solving; *Reinforcement (Psychology) |
| Abstract |
Although reinforcement often leads to repetitive, even stereotyped responding, that is not a necessary outcome. When it depends on variations, reinforcement results in responding that is diverse, novel, indeed unpredictable, with distributions sometimes approaching those of a random process. This article reviews evidence for the powerful and precise control by reinforcement over behavioral variability, evidence obtained from human and animal-model studies, and implications of such control. For example, reinforcement of variability facilitates learning of complex new responses, aids problem solving, and may contribute to creativity. Depression and autism are characterized by abnormally repetitive behaviors, but individuals afflicted with such psychopathologies can learn to vary their behaviors when reinforced for so doing. And reinforced variability may help to solve a basic puzzle concerning the nature of voluntary action. |
| Address |
Department of Psychology, Reed College, Portland, OR 97202, USA. allen.neuringer@reed.edu |
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English |
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0003-066X |
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PMID:15584823 |
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no |
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Equine Behaviour @ team @ |
Serial |
4106 |
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| Author |
Brosnan, S.F.; Freeman, C.; De Waal, F.B.M. |
| Title |
Partner's behavior, not reward distribution, determines success in an unequal cooperative task in capuchin monkeys |
Type |
Journal Article |
| Year |
2006 |
Publication |
American journal of primatology |
Abbreviated Journal |
Am. J. Primatol. |
| Volume |
68 |
Issue |
7 |
Pages |
713-724 |
| Keywords |
Animals; Behavior, Animal/*physiology; Cebus/*physiology; *Cooperative Behavior; Female; Food Preferences/physiology; Male; *Reward |
| Abstract |
It was recently demonstrated that capuchin monkeys notice and respond to distributional inequity, a trait that has been proposed to support the evolution of cooperation in the human species. However, it is unknown how capuchins react to inequitable rewards in an unrestricted cooperative paradigm in which they may freely choose both whether to participate and, within the bounds of their partner's behavior, which reward they will receive for their participation. We tested capuchin monkeys with such a design, using a cooperative barpull, which has been used with great success in the past. Contrary to our expectations, the equity of the reward distribution did not affect success or pulling behavior. However, the behavior of the partner in an unequal situation did affect overall success rates: pairs that had a tendency to alternate which individual received the higher-value food in unequal reward situations were more than twice as successful in obtaining rewards than pairs in which one individual dominated the higher-value food. This ability to equitably distribute rewards in inherently biased cooperative situations has profound implications for activities such as group hunts, in which multiple individuals work together for a single, monopolizable reward. |
| Address |
Living Links Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA. sbrosna@emory.edu |
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English |
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0275-2565 |
ISBN |
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| Notes |
PMID:16786518 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
160 |
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| Author |
Baker, K.C.; Seres, E.; Aureli, F.; De Waal, F.B. |
| Title |
Injury risks among chimpanzees in three housing conditions |
Type |
Journal Article |
| Year |
2000 |
Publication |
American journal of primatology |
Abbreviated Journal |
Am. J. Primatol. |
| Volume |
51 |
Issue |
3 |
Pages |
161-175 |
| Keywords |
Aggression; *Animal Welfare; Animals; Female; *Housing, Animal; Male; *Pan troglodytes; Risk Assessment; Wounds and Injuries/*veterinary |
| Abstract |
Meeting the psychological needs of chimpanzees (Pan troglodytes) can be a challenge given their aggressiveness on the one hand and the complexity of their social lives on the other. It is unclear how to balance the need to provide opportunities for species-appropriate behavior against potential risks of injury chimpanzees may inflict on each other. This study evaluates the suggestion that simpler social environments protect chimpanzees from wounding. Over a two-year period all visible injuries to 46 adult males, 64 adult females, and 25 immature chimpanzees were recorded at the Yerkes Regional Primate Research Center. Approximately half of the subjects were mother-reared, and the rest were nursery-reared. Housing included compounds containing about 20 chimpanzees, interconnected indoor-outdoor runs for groups of up to 12 individuals, and smaller indoor-outdoor runs for pairs and trios. Annual wounding rates were calculated for serious wounds (extensive injuries and all those requiring veterinary intervention) as well as for minor wounds. Compound-housed chimpanzees incurred the highest level of minor wounding, but serious wounding levels were not affected by housing condition. Even with a period of dominance instability and elevated levels of wounding in one compound, compound chimpanzees were not injured more than those in smaller social groups over the long term. Nursery-reared females in moderate-sized groups were wounded more than mother-reared females. Also, nursery-reared males and females were wounded less often when paired with mother-reared companions. Overall, this study indicates that maintaining chimpanzees in pairs and trios would not be an effective means for reducing injuries. The management of wounding in chimpanzee colonies is influenced more by the sex and rearing composition of a colony. |
| Address |
Living Links Center, Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia 30322, USA. kateb@rmy.emory.edu |
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English |
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0275-2565 |
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| Notes |
PMID:10902665 |
Approved |
no |
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refbase @ user @ |
Serial |
188 |
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| Author |
de Waal, F.B.; Seres, M. |
| Title |
Propagation of handclasp grooming among captive chimpanzees |
Type |
Journal Article |
| Year |
1997 |
Publication |
American journal of primatology |
Abbreviated Journal |
Am. J. Primatol. |
| Volume |
43 |
Issue |
4 |
Pages |
339-346 |
| Keywords |
Animals; Family Relations; Female; *Grooming; Learning; Male; Pan troglodytes/*psychology; *Social Behavior |
| Abstract |
A grooming posture previously reported for two wild chimpanzee (Pan troglodytes) communities developed spontaneously in a captive group of the same species. This offered a unique opportunity to follow the propagation of a new social custom. The posture consists of two partners grasping hands--either both right hands or both left hands--and raising the arms in an A-frame above their heads while mutually grooming with their free hands. The propagation of this pattern was followed over a 5 year period. In the beginning, handclasps were always initiated by the same adult female. This female initiated the posture mainly with her adult female kin. In subsequent years, these relatives became frequent participants in the posture with each other as well as with nonrelatives. Over the years the posture increased in frequency and duration and spread to the majority of adults and also to a few adolescents and older juveniles. The pattern persisted after removal of the apparent originator. |
| Address |
Yerkes Primate Center, Emory University, Atlanta, GA 30329, USA. dewaal@emory.edu |
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English |
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0275-2565 |
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| Notes |
PMID:9403098 |
Approved |
no |
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refbase @ user @ |
Serial |
202 |
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