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Matsumura, S., & Kobayashi, T. (1998). A game model for dominance relations among group-living animals. Behav. Ecol. Sociobiol., 42(2), 77–84.
Abstract: Abstract We present here an attempt to understand behaviors of dominant individuals and of subordinate individuals as behavior strategies in an asymmetric “hawk-dove” game. We assume that contestants have perfect information about relative fighting ability and the value of the resource. Any type of asymmetry, both relevant to and irrelevant to the fighting ability, can be considered. It is concluded that evolutionarily stable strategies (ESSs) depend on the resource value (V), the cost of injury (D), and the probability that the individual in one role will win (x). Different ESSs can exist even when values of V, D, and x are the same. The characteristics of dominance relations detected by observers may result from the ESSs that the individuals are adopting. The model explains some characteristics of dominance relations, for example, the consistent outcome of contests, the rare occurrence of escalated fights, and the discrepancy between resource holding potential (RHP) and dominance relations, from the viewpoint of individual selection.
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Keil, N. M., Sambraus, H.H. (1998). “Intervenors” in agonistic interactions amongst domesticated goats. Z. Säugetierk., 63(5), 266–272.
Abstract: Social behaviour was observed in individually marked goats in two herds. The goats from one herd (n = 98) were horned, those of the other herd (n = 83) were polled. By recording agonistic interactions within the herds, a dominance index was determined for each animal. In both herds, intervention took place. Intervention is defined as one animal pushing in between two fighters, and thus ending the fight. More cases of intervention took place per individual animal amongst the horned goats than amongst the polled ones. Goats which intervened in fights on several occasions usually had a high dominance index. Members of the herd which were observed intervening only once had an average dominance index in both herds of almost 0.5. In some cases, goats very low in the rank order intervened a fight. Only rarely did the intervenors have a lower dominance index than the two fighters. In 103 cases, the direct dominance relationship between a fighting animal and the intervenor was known. In 95 cases (92.2%), the intervenor was dominant to the herd member in this fight and in just eight cases (7.8%), it was subordinate. It could not be determined what advantage the intervenor gained from its activity. It is possible that, at least in certain cases, a particularly relationship existed between the intervenor and one of the fighters.
Keywords: Behaviour; Domestication; Goat; Intervention; Rank order
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Dugatkin, L. A. (1998). Breaking up fights between others: a model of intervention behaviour. Proc. R. Soc. Lond. B, 265(1394), 433–437.
Abstract: To examine when and why animals break up fights between others in their group, I modelled whether ‘winner’ and ‘loser’ effects might be one element driving the evolution of intervention behaviour. I considered one particular type of intervention: when the intervener simply breaks up fights between two others, but does not favour either party in so doing. When victories at time T + 1 are more likely given a victory at time T (i.e. winner effects), intervention is often favoured. Intervention is favoured in these circumstances because the intervening party in essence stops others from ‘getting on a roll’ and climbing up any hierarchy that exists. However, when loser effects alone are at work (defeats at time T + 1 are more likely given a defeat at time T), breaking up fights between others is never selected. If both winner and loser effects are operating simultaneously, then the likelihood of intervention behaviour evolving is a function of the relative strength of these two effects. The greater the winner effect relative to the loser effect, the more likely intervention behaviour is to evolve.
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Henzi, S. P., Lycett, J. E., & Weingrill, T. (1998). Mate guarding and risk assessment by male mountain baboons during inter-troop encounters. Anim. Behav., 55(6), 1421–1428.
Abstract: Aggressive herding of females is a frequent but not invariant response by male savannah baboons,Papio cynocephalus, to encounters with other troops. While males in some troops are consistently more likely to herd than those in others, not all inter-troop encounters result in herding, even within particular troops. This suggests that males assess the risk of male invasion posed by each encounter and respond accordingly. We used data from baboon troops in the Drakensberg mountains to determine the rules males follow in deciding whether to herd. Consistent differences between troops were explained only by the adult sex ratio. Males were more likely to herd if the sex ratio of their own troop was female biased, a finding that is concordant with the observation that males are more likely to immigrate into troops where the sex ratio is more female biased than the population average. Differences within troops were a consequence only of encounter distance, with herding being more likely at closer distances. We found a negative correlation between the angle of approach to the other troop and the subsequent angle of deflection. We interpret this to mean that herding functions to increase the distance between the interacting troops, thereby curtailing opportunities for strange males to inspect the troop and determine its sex ratio. In this way, possibly unlike those in other populations, the decision rules of these male baboons are geared to protecting longer-term reproductive prospects.
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Wittling, W., Block, A., Schweiger, E., & Genzel, S. (1998). Hemisphere Asymmetry in Sympathetic Control of the Human Myocardium. Brain Cogn., 38(1), 17–35.
Abstract: Hemisphere asymmetry in sympathetic control of myocardial performance was studied in healthy human subjects using lateralized film presentation for selective sensory stimulation of the hemispheres and impedance cardiography for the evaluation of cardiac output, systolic time intervals and myocardial contractility. Results revealed a clear and consistent right hemisphere predominance in sympathetically mediated control of various components of myocardial performance. There is reason to assume that the obtained hemisphere differences in autonomic control of the heart are self-reliant processes not depending on emotion-related hemisphere asymmetry. As far as we know, this is the first study examining the distinct roles of the cerebral hemispheres in neural control of ventricular myocardial functions.
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Potts, R. (1998). Variability selection in hominid evolution. Evol. Anthropol., 7(3), 81–96.
Abstract: Variability selection (abbreviated as VS) is a process considered to link adaptive change to large degrees of environment variability. Its application to hominid evolution is based, in part, on the pronounced rise in environmental remodeling that took place over the past several million years. The VS hypothesis differs from prior views of hominid evolution, which stress the consistent selective effects associated with specific habitats or directional trends (e.g., woodland, savanna expansion, cooling). According to the VS hypothesis, wide fluctuations over time created a growing disparity in adaptive conditions. Inconsistency in selection eventually caused habitat-specific adaptations to be replaced by structures and behaviors responsive to complex environmental change. Key hominid adaptations, in fact, emerged during times of heightened variability. Early bipedality, encephalized brains, and complex human sociality appear to signify a sequence of VS adaptations—i.e., a ratcheting up of versatility and responsiveness to novel environments experienced over the past 6 million years. The adaptive results of VS cannot be extrapolated from selection within a single environmental shift or relatively stable habitat. If some complex traits indeed require disparities in adaptive setting (and relative fitness) in order to evolve, the VS idea counters the prevailing view that adaptive change necessitates long-term, directional consistency in selection. © 1998 Wiley-Liss, Inc.
Keywords: variability selection; hominids; environment; adaptation; natural selection; evolution
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Barton, N. (1998). Evolutionary biology: The geometry of adaptation. Nature, 395(6704), 751–752. |
Weng, R. C., Edwards, S. A., & English, P. R. (1998). Behaviour, social interactions and lesion scores of group-housed sows in relation to floor space allowance. Appl. Anim. Behav. Sci., 59(4), 307–316.
Abstract: The space allowance appropriate for sows in group housing remains scientifically undefined, since the social space requirement of a group of animals and the factors which affect this are unknown. Eight established groups of six pregnant, multiparous sows were used in a replicated Latin Square design of experiment, with 7 day periods, to compare four pen sizes providing 2.0, 2.4, 3.6 or 4.8 m2/sow. For the last 48 h of each 7 day period, a continuous video recording was made to determine general behaviour and all social interactions. Time spent rooting increased progressively with increasing space allowance, whereas time spent sitting and standing inactive were both progressively reduced. The total frequency of social interactions and aggressive behaviour both increased with decreasing space allowance. The Attack:Retreat ratio was significantly higher, and the Avoidance Index significantly lower, in the smallest pen. All body regions had the highest count of lesions after sows had been in the smallest pen, with damage levels being reduced as pen area increased. Analysis of body lesion scores, combining incidence and severity, gave the same treatment effects. In conclusion, the results indicated that a minimum space of between 2.4 and 3.6 m2/sow was necessary in the conditions of this experiment to promote good welfare. This result cannot be generalised to situations of different group size, group stability or feeding method.
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Schwartz, E. B., Granger, D. A., Susman, E. J., Gunnar, M. R., & Laird, B. (1998). Assessing Salivary Cortisol in Studies of Child Development. Child Development, 69(6), 1503–1513.
Abstract: In a series of studies, we evaluated the susceptibility of radioimmunoassays (RIA) for saliva cortisol to interference effects caused by oral stimulants used to facilitate saliva collection in studies with children. When added directly to saliva samples, oral stimulants (drink mix crystals) artificially inflated estimated cortisol concentrations. The magnitude of the interference effect was concentration-dependent and more pronounced for some stimulants and RIA procedures than for others. Analysis of samples collected using oral stimulants from child and adult participants confirmed stimulant interference as an extraneous source of variability in measured saliva cortisol. Associations between serum and saliva cortisol and between saliva cortisol and “behavioral” variables were attenuated by stimulant interference. A survey of six large child studies estimated interference effects, indexed by low sample pH, to be present in 14.7% of the 1,148 total saliva samples, or 2%-54% (M= 22%) of samples within each study. Recommendations to minimize the impact of stimluant interference in studies involving salivary cortisol in the context of child health and development are outlined.
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Byrne, R. W., & Russon, A. E. (1998). Learning by imitation: a hierachical approach. Behav. Brain Sci., 21, 667–721. |