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Smith, J.E.; Kolowski, J.M.; Graham, K.E.; Dawes, S.E.; Holekamp, K.E. |
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Title |
Social and ecological determinants of fission-fusion dynamics in the spotted hyaena |
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2008 |
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Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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76 |
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3 |
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619-636 |
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competition; conflict resolution; cooperative hunting; Crocuta crocuta; ecological constraints; group living; social rank |
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Theory predicts that individuals living in fission-fusion societies, in which group members frequently change subgroups, should modify grouping patterns in response to varying social and environmental conditions. Spotted hyaenas, Crocuta crocuta, are long-lived carnivores that reside in permanent social groups called clans. Clans are complex, fission-fusion societies in which individual members travel, rest and forage in subgroups that frequently change composition. We studied two clans in Kenya to provide the first detailed description of fission-fusion dynamics in this species. Because social and ecological circumstances can influence the cohesiveness of animal societies, we evaluated the extent to which specific circumstances promote the formation of subgroups of various sizes. We found that cooperative defence of shared resources during interclan competition and protection from lions were cohesive forces that promoted formation of large subgroups. We also tested hypotheses suggesting factors limiting subgroup size. Mothers with small cubs avoided conspecifics, thereby reducing infanticide risk. Victims of aggression either reconciled fights or separated from former opponents to reduce the immediate costs of escalated aggression in the absence of food. As predicted by the ecological constraints hypothesis, hyaenas adjusted their grouping patterns over both short and long time scales in response to feeding competition. Crocuta were most gregarious during periods of abundant prey, joined clanmates at ephemeral kills in numbers that correlated with the energetic value of the prey and gained the most energy when foraging alone because cooperative hunting attracted numerous competitors. Overall, our findings indicate that resource limitation constrains grouping in this species. |
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Equine Behaviour @ team @ |
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4676 |
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Sawaguchi, T.; Kudo, H. |
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Title |
Neocortical development and social structure in primates |
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1990 |
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Primates |
Abbreviated Journal |
Primates |
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31 |
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2 |
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283-289 |
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Neocortex – Relative size – Allometry – Congeneric group – Social structure – Monogyny – Polygyny – Primates |
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Abstract  The relationships between the relative size of the neocortex and differences in social structures were examined in prosimians and anthropoids. The relative size of the neocortex (RSN) of a given congeneric group in each superfamily of primates was measured based on the allometric relationships between neocortical volume and brain weight for each superfamily, to control phylogenetic affinity and the effects of brain size. In prosimians, “troop-making†congeneric groups (N=3) revealed a significantly larger RSN than solitary groups (N=6), and there was a significant, positive correlation between RSN and troop size. In the case of anthropoids, polygynous/frugivorous groups (N=5) revealed a significantly larger RSN than monogynous/frugivorous groups (N=8). Furthermore, a significant, positive correlation between RSN and troop size was found for frugivorous congeneric groups of the Ceboidea. These results suggest that neocortical development is associated with differences in social structure among primates. |
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Equine Behaviour @ team @ |
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4799 |
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Conradt, L.; Roper, T.J. |
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Title |
Deciding group movements: Where and when to go |
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2010 |
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Behavioural Processes |
Abbreviated Journal |
Behav. Process. |
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84 |
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3 |
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675-677 |
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activity synchronisation; aggregation rules; collective decisions; democracy; group decisions; sexual segregation; decision sharing; social choice theory |
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A group of animals can only move cohesively, if group members “somehow” reach a consensus about the timing (e.g., start) and the spatial direction/destination of the collective movement. Timing and spatial decisions usually differ with respect to the continuity of their cost/benefit distribution in such a way that, in principle, compromises are much more feasible in timing decision (e.g. median preferred time) than they are in spatial decisions. The consequence is that consensus costs connected to collective timing decisions are usually less skewed amongst group members than are consensus costs connected to spatial decisions. This, in turn, influences the evolution of decision sharing: sharing in timing decisions is most likely to evolve when conflicts are high relative to group cohesion benefits, while sharing in spatial decisions is most likely to evolve in the opposite situation. We discuss the implications of these differences for the study of collective movement decisions. |
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0376-6357 |
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Equine Behaviour @ team @ |
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5086 |
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Jørgensen, G.H.M.; Borsheim, L.; Mejdell, C.M.; Søndergaard, E.; Bøe, K.E. |
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Grouping horses according to gender--Effects on aggression, spacing and injuries |
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2009 |
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Applied Animal Behaviour Science |
Abbreviated Journal |
Appl. Anim. Behav. Sci. |
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120 |
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1-2 |
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94-99 |
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Horse; Group housing; Gender; Injuries; Social behaviour |
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Many horse owners tend to group horses according to gender, in an attempt to reduce aggressive interactions and the risk of injuries. The aim of our experiment was to test the effects of such gender separation on injuries, social interactions and individual distance in domestic horses. A total of 66 horses were recruited from 4 different farms in Norway and Denmark and divided into six batches. Within each batch, horses were allotted into one mare group, one gelding group and one mixed gender group, with most groups consisting of three or four animals. After 4-6 weeks of acclimatisation, a trained observer recorded all social interactions using direct, continuous observation 1 h in the morning and 1 h in the afternoon for three consecutive days. Recordings of the nearest neighbour of each horse were performed using instantaneous sampling every 10 min. The horses were inspected for injuries before grouping, day 1 after grouping and after 4-6 weeks. No significant effect of gender composition was found on social interactions (P > 0.05), spacing (P > 0.07) or injuries (P > 0.23). Eighty percent of all aggressive interactions recorded were threats, not involving physical contact. Horses with the smallest space allowance showed the highest mean number of aggressive interactions (28.6 ± 6.1 interactions per 6 h) compared to the mean of all the other batches (8.3 ± 1.0 interactions per 6 h). Very few injuries were found and most were superficial. In conclusion, gender composition does not seem to have any effect on aggression level, spacing or injuries. However, the early social experience of horses, management of feeding and space allowance probably represents more important factors for successful group housing of domestic horses. |
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0168-1591 |
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Equine Behaviour @ team @ |
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5093 |
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Zharkikh, T.L.; Andersen, L. |
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Behaviour of Bachelor Males of the Przewalski Horse (Equus ferus przewalskii) at the Reserve Askania Nova |
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2009 |
Publication |
Der Zoologische Garten |
Abbreviated Journal |
Zoologische Garten |
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78 |
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5-6 |
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282-299 |
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Equid; Przewalski horse (Equus ferus przewalskii); Bachelor group; Social behaviour |
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The aim of this study was to investigate social relationships between Przewalski horses at a high density in a bachelor group housed in a 3.5-ha enclosure. The group consisted of 16 males aged 5 to 16. Behavioural data were collected during 18 days, total 216 h. Fifteen minute focal animal sampling was used; each horse was observed three times a day for a total of 45 min. The occurrence of 25 behaviours was recorded, and group spacing behaviour was studied using nearest neighbour recordings. The group divided into four subgroups; this supports earlier findings of bachelor groups (n>=10) dividing into two or more subgroups if they included several males aged >5 years. The total frequency of social interactions was 14.6±1.1 h-1. Although the density of the group in this study was higher than in other zoos, the males interacted agonistically only 3.6 h-1. The most frequently observed social behaviour categories were friendly interactions. This study shows possibilities to use some investigative behaviours (marking, flehmen, olfactory investigation, etc.) as indicators of social status of animals in a group. |
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0044-5169 |
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Equine Behaviour @ team @ |
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5098 |
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Lusseau, D.; Conradt, L. |
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The emergence of unshared consensus decisions in bottlenose dolphins |
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2009 |
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Behavioral Ecology and Sociobiology |
Abbreviated Journal |
Behav. Ecol. Sociobiol. |
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63 |
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7 |
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1067-1077 |
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Behavioral ecology – Decision-making process – Bottlenose dolphin – Group living |
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Abstract Unshared consensus decision-making processes, in which one or a small number of individuals make the decision for the rest of a group, are rarely documented. However, this mechanism can be beneficial for all group members when one individual has greater knowledge about the benefits of the decision than other group members. Such decisions are reached during certain activity shifts within the population of bottlenose dolphins residing in Doubtful Sound, New Zealand. Behavioral signals are performed by one individual and seem to precipitate shifts in the behavior of the entire group: males perform side flops and initiate traveling bouts while females perform upside-down lobtails and terminate traveling bouts. However, these signals are not observed at all activity shifts. We find that, while side flops were performed by males that have greater knowledge than other male group members, this was not the case for females performing upside-down lobtails. The reason for this could have been that a generally high knowledge about the optimal timing of travel terminations rendered it less important which individual female made the decision. |
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Equine Behaviour @ team @ |
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5109 |
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Conradt, L.; Krause, J.; Couzin, I. D.; Roper, T. J. |
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Title |
“Leading According to Need” in Self-Organizing Groups |
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2009 |
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The American Naturalist |
Abbreviated Journal |
Am Nat |
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173 |
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3 |
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304-312 |
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behavioral synchrony, collective group decisions, democracy and egalitarianism in animals, public goods experiments, sexual segregation, social choice theory |
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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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Equine Behaviour @ team @ |
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5121 |
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Dyer, J.R.G.; Johansson, A.; Helbing, D.; Couzin, I.D.; Krause, J. |
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Leadership, consensus decision making and collective behaviour in humans |
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2009 |
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Philosophical Transactions of the Royal Society B: Biological Sciences |
Abbreviated Journal |
Phil. Trans. Biol. Sci. |
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364 |
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1518 |
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781-789 |
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* leadership * consensus decision making * collective behaviour * human group |
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This paper reviews the literature on leadership in vertebrate groups, including recent work on human groups, before presenting the results of three new experiments looking at leadership and decision making in small and large human groups. In experiment 1, we find that both group size and the presence of uninformed individuals can affect the speed with which small human groups (eight people) decide between two opposing directional preferences and the likelihood of the group splitting. In experiment 2, we show that the spatial positioning of informed individuals within small human groups (10 people) can affect the speed and accuracy of group motion. We find that having a mixture of leaders positioned in the centre and on the edge of a group increases the speed and accuracy with which the group reaches their target. In experiment 3, we use large human crowds (100 and 200 people) to demonstrate that the trends observed from earlier work using small human groups can be applied to larger crowds. We find that only a small minority of informed individuals is needed to guide a large uninformed group. These studies build upon important theoretical and empirical work on leadership and decision making in animal groups. |
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Equine Behaviour @ team @ |
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5122 |
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King, A.J.; Douglas, C.M.S.; Huchard, E.; Isaac, N.J.B.; Cowlishaw, G. |
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Dominance and affiliation mediate despotism in a social primate |
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2008 |
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Current Biology : CB |
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Curr Biol |
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18 |
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23 |
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1833-1838 |
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Animals; *Authoritarianism; Behavior, Animal/*physiology; Cooperative Behavior; *Decision Making; Feeding Behavior; Female; *Group Processes; Male; Papio ursinus/*psychology; *Social Dominance |
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Group-living animals routinely have to reach a consensus decision and choose between mutually exclusive actions in order to coordinate their activities and benefit from sociality. Theoretical models predict “democratic” rather than “despotic” decisions to be widespread in social vertebrates, because they result in lower “consensus costs”-the costs of an individual foregoing its optimal action to comply with the decision-for the group as a whole. Yet, quantification of consensus costs is entirely lacking, and empirical observations provide strong support for the occurrence of both democratic and despotic decisions in nature. We conducted a foraging experiment on a wild social primate (chacma baboons, Papio ursinus) in order to gain new insights into despotic group decision making. The results show that group foraging decisions were consistently led by the individual who acquired the greatest benefits from those decisions, namely the dominant male. Subordinate group members followed the leader despite considerable consensus costs. Follower behavior was mediated by social ties to the leader, and where these ties were weaker, group fission was more likely to occur. Our findings highlight the importance of leader incentives and social relationships in group decision-making processes and the emergence of despotism. |
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Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK. andrew.king@ioz.ac.uk |
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0960-9822 |
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PMID:19026539 |
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Equine Behaviour @ team @ |
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5124 |
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Jacobs, A.; Maumy, M.; Petit, O. |
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The influence of social organisation on leadership in brown lemurs (Eulemur fulvus fulvus) in a controlled environment |
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2008 |
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Behavioural Processes |
Abbreviated Journal |
Behav. Process. |
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79 |
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2 |
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111-113 |
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Animals; *Decision Making; Dominance-Subordination; *Exploratory Behavior; Female; Group Structure; *Leadership; Lemur/*psychology; Male; Sex Factors; *Social Environment |
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Studies on leadership during group movements in several lemur species showed that females were responsible for the travelling choices concerning time and direction. Interestingly, in these species females are dominant over males. We investigated the influence of social organisation upon leadership processes by studying a lemur species in which social organisation is characterized by the absence of female dominance: the brown lemur (Eulemur fulvus fulvus). The study was conducted on a semi-free ranging group of 11 individuals and the analysis performed on 69 group movements showed that all the individuals could initiate a group movement. In 34 cases, the whole group moved. There was no significant difference in the number of start attempts or in the number of group members involved from one initiator to another. Moreover, there was no effect of sex or age of the initiator on the number of individuals following it or on the speed of the joining process. Therefore, the leadership observed is widely distributed to all group members. These results support the hypothesis of an influence of social organisation upon the decision-making processes but still remain to be studied in a more relevant ecological context. |
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IPHC-DEPE, Equipe d'ethologie des primates, UMR 7178, Centre National de la Recherche Scientifique-Universite Louis Pasteur and Centre de Primatologie, Strasbourg, France |
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0376-6357 |
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PMID:18586413 |
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Equine Behaviour @ team @ |
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5127 |
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