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Bergman, T. J., Beehner, J. C., Cheney, D. L., & Seyfarth, R. M. (2003). Hierarchical classification by rank and kinship in baboons. Science, 302(5648), 1234–1236.
Abstract: Humans routinely classify others according to both their individual attributes, such as social status or wealth, and membership in higher order groups, such as families or castes. They also recognize that people's individual attributes may be influenced and regulated by their group affiliations. It is not known whether such rule-governed, hierarchical classifications are specific to humans or might also occur in nonlinguistic species. Here we show that baboons recognize that a dominance hierarchy can be subdivided into family groups. In playback experiments, baboons respond more strongly to call sequences mimicking dominance rank reversals between families than within families, indicating that they classify others simultaneously according to both individual rank and kinship. The selective pressures imposed by complex societies may therefore have favored cognitive skills that constitute an evolutionary precursor to some components of human cognition.
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Izar, P., Ferreira, R. G., & Sato, T. (2006). Describing the organization of dominance relationships by dominance-directed tree method. Am. J. Primatol., 68(2), 189–207.
Abstract: Methods to describe dominance hierarchies are a key tool in primatology studies. Most current methods are appropriate for analyzing linear and near-linear hierarchies; however, more complex structures are common in primate groups. We propose a method termed “dominance-directed tree.” This method is based on graph theory and set theory to analyze dominance relationships in social groups. The method constructs a transitive matrix by imposing transitivity to the dominance matrix and produces a graphical representation of the dominance relationships, which allows an easy visualization of the hierarchical position of the individuals, or subsets of individuals. The method is also able to detect partial and complete hierarchies, and to describe situations in which hierarchical and nonhierarchical principles operate. To illustrate the method, we apply a dominance tree analysis to artificial data and empirical data from a group of Cebus apella.
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Li, F. - H., Zhong, W. - Q., Wang, Z., & Wang, D. - H. (2007). Rank in a food competition test and humoral immune functions in male Brandt's voles (Lasiopodomys brandtii). Physiol. Behav., 90(2-3), 490–495.
Abstract: Social status can influence an animal's immune and reproductive functions, eventually leading to alterations in immunocompetence and reproductive success. Here, we report that rank assessed in a food competition test, considered as an index of social status, has significant influences on humoral immune functions in male Brandt's voles (Lasiopodomys brandtii) living in a group. Our data reveal a negative correlation of the spleen mass and serum antibody levels with social status, as well as a positive correlation of serum cortisol levels with social status. Males winning in food competition had a smaller spleen, a lower level of serum antibodies, and a higher level of serum cortisol than did their conspecific counterparts. These data indicate interactions between social status and humoral immune functions and might illustrate a trade-off between infection risks and reproductive success in male Brandt's voles.
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Giles, N., & Tupper, J. (2006). Equine interspecies aggression (Vol. 159).
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Feist, J. D., & McCullough, D. R. (1975). Reproduction in feral horses. J Reprod Fertil Suppl, (23), 13–18.
Abstract: A behavioural study of feral horses was conducted on the Pryor Mountain Wild Horse Range in the western United States. All 270 horses on the Range were identified individually. The sex ratio was nearly balanced. Foal to adult female ratio was 43-2:100. Morality was concentrated among foals and old horses. Horses were organized as forty-four harem groups each with a dominant stallion, one to two immature stallions, one to three immature mares, one to three adult mares and their yearling and foal offspring, and 23 bachelor groups of one to eight stallions. Harem groups were quite stable year-round because of dominance and leadership by the stallions and group fidelity by mares and their offsring. Most changes occurred during the breeding season and involved immature females. Defeat of dominant stallions was infrequent. Immature males were tolerated because of their submissive behaviour. Bachelor stallion groups were inherently unstable. Mares came into heat after foaling in May/June, and were mated by harem stallions only.
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Mitman, G. (1990). Dominance, leadership, and aggression: animal behavior studies during the Second World War. J Hist Behav Sci, 26(1), 3–16.
Abstract: During the decade surrounding the Second World War, an extensive literature on the biological and psychological basis of aggression surfaced in America, a literature that in general emphasized the significance of learning and environment in the origins of aggressive behavior. Focusing on the animal behavior research of Warder Clyde Allee and John Paul Scott, this paper examines the complex interplay among conceptual, institutional, and societal forces that created and shaped a discourse on the subjects of aggression, dominance, and leadership within the context of World War II. The distinctions made between sexual and social dominance during this period, distinctions accentuated by the threat of totalitarianism abroad, and the varying ways that interpretations of behavior could be negotiated attests to the multiplicity of interactions that influence the development of scientific research.
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Dunbar, R. I., & Dunbar, E. P. (1976). Contrasts in social structure among black-and-white colobus monkey groups. Anim. Behav., 24(1), 84–92.
Abstract: Three types of Colobus guereza groups may be distinguished on the bases of size and composition, namely small one-male groups, large, one-male groups and multi-male groups. The social structure of each type of group is described in terms of the distribution of non-agonistic interactions, the frequency and distribution of agonistic behaviour and the organization of the roles of vigilance, territorial defence and leadership. A number of differences are found between the group types which appear to be related to the differences in group size and composition. It is suggested that these group types represent stages in the life-cycle of colobus groups, and that such an interpretation may help to resolve some of the conflicting reports in the literature.
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Saayman, G. S. (1971). Behaviour of the adult males in a troop of free-ranging Chacma baboons (Papio ursinus). Folia Primatol (Basel), 15(1), 36–57.
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Gajdon, G. K., Fijn, N., & Huber, L. (2006). Limited spread of innovation in a wild parrot, the kea (Nestor notabilis). Anim. Cogn., 9(3), 173–181.
Abstract: In the local population of kea in Mount Cook Village, New Zealand, some keas open the lids of rubbish bins with their bill to obtain food scraps within. We investigated the extent to which this innovation has spread in the local population, and what factors limit the acquisition of bin opening. Only five males of 36 individually recognised birds were observed to have performed successful bin opening. With one exception there were always other keas present, watching successful bin opening. Seventeen additional individuals were seen to have benefitted from lid opening. Their foraging success was less than that of the bin openers. Social status of bin openers did not differ from scrounging males. Among the individuals that were regularly seen at the site of the bins but were not successful in bin opening, social status and the ratio of feeding directly from open bins correlated with the amount of opening attempts. We conclude that scrounging facilitated certain behavioural aspects of bin opening rather than inhibiting them. The fact that only 9% of opening attempts were successful, and the long period of time required to increase efficiency in lid opening shows that mainly individual experience, and to a lesser extent insight and social learning, play key roles in acquisition of the opening technique. The results indicate that the spread of innovative solutions of challenging mechanical problems in animals may be restricted to only a few individuals.
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Overli, O., Sorensen, C., Pulman, K. G. T., Pottinger, T. G., Korzan, W., Summers, C. H., et al. (2007). Evolutionary background for stress-coping styles: relationships between physiological, behavioral, and cognitive traits in non-mammalian vertebrates. Neurosci Biobehav Rev, 31(3), 396–412.
Abstract: Reactions to stress vary between individuals, and physiological and behavioral responses tend to be associated in distinct suites of correlated traits, often termed stress-coping styles. In mammals, individuals exhibiting divergent stress-coping styles also appear to exhibit intrinsic differences in cognitive processing. A connection between physiology, behavior, and cognition was also recently demonstrated in strains of rainbow trout (Oncorhynchus mykiss) selected for consistently high or low cortisol responses to stress. The low-responsive (LR) strain display longer retention of a conditioned response, and tend to show proactive behaviors such as enhanced aggression, social dominance, and rapid resumption of feed intake after stress. Differences in brain monoamine neurochemistry have also been reported in these lines. In comparative studies, experiments with the lizard Anolis carolinensis reveal connections between monoaminergic activity in limbic structures, proactive behavior in novel environments, and the establishment of social status via agonistic behavior. Together these observations suggest that within-species diversity of physiological, behavioral and cognitive correlates of stress responsiveness is maintained by natural selection throughout the vertebrate sub-phylum.
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