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Kitchen, D. M., Cheney, D. L., & Seyfarth, R. M. (2005). Male chacma baboons (Papio hamadryas ursinus) discriminate loud call contests between rivals of different relative ranks. Anim. Cogn., 8(1), 1–6.
Abstract: Males in multi-male groups of chacma baboons (Papio hamadryas ursinus) in Botswana compete for positions in a linear dominance hierarchy. Previous research suggests that males treat different categories of rivals differently; competitive displays between males of similar rank are more frequent and intense than those between disparately ranked males. Here we test whether males also respond differently to male-male interactions in which they are not directly involved, using playbacks of the loud 'wahoo' calls exchanged between competing males in aggressive displays. We played paired sequences of vocal contests between two adjacently ranked and two disparately ranked males to ten subjects, half ranking below the signalers in the call sequences and half above. Subjects who ranked above the two signalers showed stronger responses than lower-ranking subjects. Higher-ranking subjects also responded more strongly to sequences involving disparately ranked, as opposed to adjacently ranked opponents, suggesting that they recognized those individuals' relative ranks. Strong responses to sequences between disparately ranked opponents might have occurred either because such contests typically involve resources of high fitness value (defense of meat, estrous females or infants vulnerable to infanticide) or because they indicate a sudden change in one contestant's condition. In contrast, subjects who ranked lower than the signalers responded equally strongly to both types of sequences. These subjects may have been able to distinguish between the two categories of opponents but did not respond differently to them because they had little to lose or gain by a rank reversal between males that already ranked higher than they did.
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Manson, J. H., Perry, S., & Stahl, D. (2005). Reconciliation in wild white-faced capuchins (Cebus capucinus). Am. J. Primatol., 65(3), 205–219.
Abstract: The likelihood of reconciliation (defined as preferential peaceful contact among former opponents following conflicts) has been predicted to vary positively with relationship value and compatibility, and negatively with relationship security. Long-term data on wild white-faced capuchins (Cebus capucinus) indicate that dyads consisting of an adult female and an alpha male have high value and compatibility, but low security. Two studies of C. capucinus postconflict (PC) behavior were carried out at Lomas Barbudal Biological Reserve, Costa Rica. One study consisted of 30-min PC and matched control (MC) follows. The second study extracted PC and MC periods from long follows, yielding PC/MC periods averaging 105 min. In study 2, but not study 1, significantly more PC/MC pairs were attracted (former opponents affiliated with each other sooner in the PC period than in the MC period) than were dispersed (former opponents affiliated with each other sooner in the MC period than in the PC period). Reconciliation in study 2 could not be explained as a by-product of former opponents' tendency to seek affiliative contact with conspecifics generally, or of the spatial proximity of opponents following conflicts. Attempted reconciliation was less likely to be followed by renewed aggression when reconciliation attempts were delayed following conflicts. The data were insufficient for a formal test of differences in conciliatory tendency (the difference between the number of attracted and dispersed PC/MC pairs, divided by the total number of pairs) among dyad types to be conducted.
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Overdorff, D. J., Erhart, E. M., & Mutschler, T. (2005). Does female dominance facilitate feeding priority in black-and-white ruffed lemurs (Varecia variegata) in southeastern Madagascar? Am. J. Primatol., 66(1), 7–22.
Abstract: Although many Malagasy lemurs are thought to be female dominant and to have female feeding priority, to date the relationship between these behaviors has been rigorously established only in Lemur catta, and other ways that females might achieve feeding priority have not been examined closely. Erhart and Overdorff [International Journal of Primatology 20:927-940, 1999] suggested that one way female primates achieve feeding priority is to initiate and lead groups to food, thereby gaining access to the food first and positively influencing their food intake compared to other group members. Here we describe female dominance patterns and potential measures of feeding priority in two groups of black-and-white ruffed lemurs (Varecia variegata) that were observed over a 15-month period in southeastern Madagascar. We predicted that the females would 1) be consistently dominant to males, 2) lead groups to food sources more often than males, and 3) have higher feeding rates compared to males when they arrived at food sources first. The results were dissimilar between the study groups. During the study, the oldest adult female in group 1 died. There was no evidence for female dominance in this group, and the remaining (likely natal) female did not lead the group more often, nor did she have a higher food intake than males. Group 1 dispersed shortly after the time frame reported here. In contrast, the resident female in group 2 was dominant to group males (based on agonistic interactions), led the group to food sources more often, and experienced a higher food intake when she arrived first at a food source. How these patterns vary over time and are influenced by the number of females in groups, group stability, food quality, and reproductive condition will be examined in future analyses.
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Vallortigara, G., & Rogers, L. J. (2005). Survival with an asymmetrical brain: advantages and disadvantages of cerebral lateralization. Behav Brain Sci, 28(4), 575–89; discussion 589–633.
Abstract: Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an “evolutionarily stable strategy” under “social” pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species.
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Paz-y-Miño C. G., Bond, A. B., Kamil, A. C., & Balda, R. P. (2004). Pinyon jays use transitive inference to predict social dominance. Nature, 430(7001), 778–781.
Abstract: Living in large, stable social groups is often considered to favour the evolution of enhanced cognitive abilities, such as recognizing group members, tracking their social status and inferring relationships among them. An individual's place in the social order can be learned through direct interactions with others, but conflicts can be time-consuming and even injurious. Because the number of possible pairwise interactions increases rapidly with group size, members of large social groups will benefit if they can make judgments about relationships on the basis of indirect evidence. Transitive reasoning should therefore be particularly important for social individuals, allowing assessment of relationships from observations of interactions among others. Although a variety of studies have suggested that transitive inference may be used in social settings, the phenomenon has not been demonstrated under controlled conditions in animals. Here we show that highly social pinyon jays (Gymnorhinus cyanocephalus) draw sophisticated inferences about their own dominance status relative to that of strangers that they have observed interacting with known individuals. These results directly demonstrate that animals use transitive inference in social settings and imply that such cognitive capabilities are widespread among social species.
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Shettleworth, S. J. (2004). Cognitive science: rank inferred by reason. Nature, 430(7001), 732–733.
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Cloutier, S., Newberry, R. C., & Honda, K. (2004). Comparison of social ranks based on worm-running and aggressive behaviour in young domestic fowl. Behav. Process., 65(1), 79–86.
Abstract: Worm-running is behaviour in which a chick runs carrying a worm-like object while flock mates follow and attempt to grab the object from its beak. We hypothesised that social ranks based on worm-running frequency are stable over time and are positively correlated with social ranks based on success in aggressive interactions when older. At 8-12 days of age, we scored worm-running in 17 groups of 12 female White Leghorn chicks during three 10-min tests. Based on instantaneous scans at 5-s intervals, the bird carrying the `worm' most often was placed in rank one and so on down the rank order. These tests were repeated at 68-70 days of age. An aggression index for each bird was calculated as the number of aggressive acts given, divided by the number given and received, during three 1-h observation periods when the birds were 68-70 days. Ranks obtained in worm-running tests were positively correlated over the two age periods (P<0.05) but were not correlated with ranks based on the aggression index (P>0.05). Our results indicate that worm-running ranks are not predictive of success in aggressive interactions. Instead, worm-running fits some criteria for play.
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Langbein, J., & Puppe, B. (2004). Analysing dominance relationships by sociometric methods--a plea for a more standardised and precise approach in farm animals. Appl. Anim. Behav. Sci., 87(3-4), 293–315.
Abstract: Social dominance is a multidimensional phenomenon occurring in all gregarious farm animals and finds its reflection in a dominance hierarchy. Hence, numerous studies have tried to analyse dominance relationships as well as to correlate outcoming results (mostly individual ranks) with other behavioural and/or physiological features of the animals. Although the concept of dominance, once established, has been developed continuously and several sociometric measures were cumulatively introduced, a consistent analysing approach has not been achieved, especially in farm animals. Thus, considerable inconsistencies in the used methodology may impair obtained results and interpretations. The present paper is a plea for a more standardised and complex approach when analysing dominance relationships, not only in farm animals. First, derived from a structural definition of dominance, we suggest in detail the preferably consistent use of appropriate sociometric measures at all social levels of analysis: the dyad as the starting level, the group as the highest level, and the individual as the basic level. Second, we applied this procedures in a case study to analyse social dominance in a group of dwarf goats (n=12) and pigs (n=10), respectively, to comparatively demonstrate benefits and problems of such an approach in two different farm animal species. It is concluded that the use of individual ranks is actually only reasonable when fundamental sociometric measures both at the dyadic level (e.g. percentage of dyads which have a significant asymmetric outcome) and at the group level (e.g. the strength of hierarchy) are successfully tested by statistical methods as also presented in this paper. The calculated sociometric measures deliver not only a more comprehensive “picture” of the social relationships within a group as simple ranks do, but also indicate possible reasons of differences in the behavioural development. For instance, whereas the dwarf goats maintained a quasi-linear dominance hierarchy over time with a high rate of overt agonistic behaviour, pigs after the establishment of their hierarchy showed a reduced agonistic behaviour which makes it questionable to calculate reliable sociometric measures. These species-dependent variations may be primarily caused by different kinds of the fighting behaviour in goats (i.e. ritualised, low costs) and pigs (i.e. more seriously, high costs). Overall, a more consistent and standardised approach of analysing social dominance in (farm) animals may improve the scientific value of single studies and makes it easier to compare various studies within a species and between species.
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Regolin, L., Marconato, F., & Vallortigara, G. (2004). Hemispheric differences in the recognition of partly occluded objects by newly hatched domestic chicks (Gallus gallus). Anim. Cogn., 7(3), 162–170.
Abstract: Domestic chicks are capable of perceiving as a whole objects partly concealed by occluders (“amodal completion”). In previous studies chicks were imprinted on a certain configuration and at test they were required to choose between two alternative versions of it. Using the same paradigm we now investigated the presence of hemispheric differences in amodal completion by testing newborn chicks with one eye temporarily patched. Separate groups of newly hatched chicks were imprinted binocularly: (1) on a square partly occluded by a superimposed bar, (2) on a whole or (3) on an amputated version of the square. At test, in monocular conditions, each chick was presented with a free choice between a complete and an amputated square. In the crucial condition 1, chicks tested with only their left eye in use chose the complete square (like binocular chicks would do); right-eyed chicks, in contrast, tended to choose the amputated square. Similar results were obtained in another group of chicks imprinted binocularly onto a cross (either occluded or amputated in its central part) and required to choose between a complete or an amputated cross. Left-eyed and binocular chicks chose the complete cross, whereas right-eyed chicks did not choose the amputated cross significantly more often. These findings suggest that neural structures fed by the left eye (mainly located in the right hemisphere) are, in the chick, more inclined to a “global” analysis of visual scenes, whereas those fed by the right eye seem to be more inclined to a “featural” analysis of visual scenes.
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Overli, O., Korzan, W. J., Hoglund, E., Winberg, S., Bollig, H., Watt, M., et al. (2004). Stress coping style predicts aggression and social dominance in rainbow trout. Horm Behav, 45(4), 235–241.
Abstract: Social stress is frequently used as a model for studying the neuroendocrine mechanisms underlying stress-induced behavioral inhibition, depression, and fear conditioning. It has previously been shown that social subordination may result in increased glucocorticoid release and changes in brain signaling systems. However, it is still an open question which neuroendocrine and behavioral differences are causes, and which are consequences of social status. Using juvenile rainbow trout of similar size and with no apparent differences in social history, we demonstrate that the ability to win fights for social dominance can be predicted from the duration of a behavioral response to stress, in this case appetite inhibition after transfer to a new environment. Moreover, stress responsiveness in terms of confinement-induced changes in plasma cortisol was negatively correlated to aggressive behavior. Fish that exhibited lower cortisol responses to a standardized confinement test were markedly more aggressive when being placed in a dominant social position later in the study. These findings support the view that distinct behavioral-physiological stress coping styles are present in teleost fish, and these coping characteristics influence both social rank and levels of aggression.
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