Dellert, B., & Ganslosser, U. (1997). Experimental alterations of food distribution in two species of captive equids (Equus burchelli and E. hemionus kulan). Ethol Ecol Evol, 9(1), 1–17.
Abstract: n one group each of Plains zebra (six mares, one foal, one subadult) and Asiatic wild asses (seven mares, two foals) at Nuremberg Zoo, food distribution was experimentally changed from clumped (all food in one standard hay rack) to dispersed (one heap per animal). Both groups were characterized by different social structures, which basically remained during the experiment. Plains zebras had an individually structured system of social relationships in a dominance order, wild asses a more egalitarian system without clear-cut rank differences and low frequencies of agonistic interactions. Access to food accordingly was individually (but consistently) different for zebra mares, almost equal for wild ass mares. During the dispersed feeding situation frequencies of agonistic interactions in both species decreased (however non-significantly), individual distances increased but mares also frequently ''visited'' each others' heaps. Feeding time increased for all wild ass mares. Some individuals (in both groups) behaved ''against the trend'' in agonistic behaviour. The results are discussed with regard to food distribution for ungulates in general, and equid social systems.
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Ellis, L. (1995). Dominance and reproductive success among nonhuman animals: A cross-species comparison. Ethol. a. Sociob., 16(4), 257–333.
Abstract: This paper updates and extends Dewsbury's (1982) review of the literature on dominance and reproductive success (RS). The findings from approximately 700 studies are included, over two thirds of which were unavailable to Dewsbury. In order to give a highly condensed and yet meaningful overview, the main findings are represented in four tables, one for male nonprimates, one for female nonprimates, one for male primates, and one for female primates. In the tables for males, findings are analyzed in terms of six different indicators of RS, and in the tables for females, in terms of eight RS indicators. Outside the primate order, evidence largely supported the hypothesis that high-ranking males enjoy greater RS than do subordinate males. For females, studies are more evenly divided between those supporting the hypothesis that high rank and RS are positively correlated and those indicating no significant rank-RS relationship. This may reflect both the lower saliency of hierarchical relationships among females, as well as the lower variability in RS among females, relative to males. Among primates, a complex picture has emerged, especially in the case of males. Much of the complexity appears due to the importance of age and seniority in affecting dominance rank. Also, in some primate species, female preferences for sex partners seem to have little to do with the male's dominance rank, at least at the time mating takes place. Nevertheless, the majority of studies suggest that high- to middle-ranking males have at least a slight lifetime reproductive advantage over the lowest ranking males.
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Boyd, R., & Richerson, P. J. (1995). Why does culture increase human adaptability? Ethol. a. Sociob., 16(2), 125–143.
Abstract: It is often argued that culture is adaptive because it allows people to acquire useful information without costly learning. In a recent paper Rogers (1989) analyzed a simple mathematical model that showed that this argument is wrong. Here we show that Rogers' result is robust. As long as the only benefit of social learning is that imitators avoid learning costs, social learning does not increase average fitness. However, we also show that social learning can be adaptive if it makes individual learning more accurate or less costly.
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Kasuya, E. (1995). A randomization test for linearity of dominance hierarchies. J. Ethol., 13(1), 137–140.
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Wolff, A., & Hausberger, M. (1994). Behaviour of foals before weaning may have some genetic basis. Ethology, 96(1), 1–10.
Abstract: In this preliminary study on foal behaviour, 13 French saddlebred foals (2-3 mo old) and their dams were observed on pasture. The most important findings are the interindividual quantitative differences in foal behaviour patterns as well as in the amount of mainly foal-initiated time spent at given distances from their mares. Interindividual differences seem in part due to a sire effect
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Sakura O, & Matsuzawa T. (1991). Flexibility of wild chimpanzees nut-cracking behavior using stone hammers and anvils: an experimental analysis. Ethology, 87, 237.
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Noë, R., van Schaik, C. P., & van Hooff, J. A. R. A. M. (1991). The Market Effect: an Explanation for Pay-off Asymmetries among Collaborating Animals. Ethology, 87(1-2), 97–118.
Abstract: Abstract * 1Animals can derive leverage over others from (a) resource holding power, based for instance on fighting ability or dominance, and (b) the possession of commodities, such as special skills and resources that cannot be taken away by force. * 2We contend that power based on the possession of commodities strongly depends on the level of supply and demand for that commodity, a phenomenon we call the ‘market effect’. * 3Several theoretical and empirical examples are given of social systems in which animals belong to two distinct classes that offer two different kinds of commodities. * 4The relative frequency of occurrence of the two classes is shown to determine the relative power of their members. * 5We consider the theoretical properties of bargaining processes by which relative power is converted into corresponding pay-off distributions. * 6We propose coalition games, a class of games with more than two players and in which bargaining is possible, as suitable paradigms for collaboration among members of social units.
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Black, J. M. (1988). Preflight Signalling in Swans: A Mechanism for Group Cohesion and Flock Formation. Ethology, 79(2), 143–157.
Abstract: Abstract The preflight behaviour of whooper swans Cygnus cygnus and Bewick's swans Cygnus columbianus bewickii was examined to determine the adaptive significance of the ritual. Analysis of the preflight sequence revealed that the rate of signalling became significantly faster as the time of takeoff approached. This provides the first quantitative evidence that a threshold of excitability is responsible for triggering synchronised flight in social units. Two ultimate and two proximate factors that affect this threshold were uncovered. They are: 1) Maintaining proximity to partners—flight was delayed by birds with non-attentive mates and signalling lasted on average four times longer than those whose mates showed more interest. 2) Maintaining flock cohesiveness—birds which performed signals for longer periods while swimming among uninterested birds were successful in attracting followers 61% of the time. 3) The bird's feeding performance related to dominance status—less successful feeders (potentially hungry birds), flew after little time and few signals. 4) The type of feeding opportunity at the eventual destination—birds which flew to provided feeds (nutritious barley) spent less time performing preflight signals than when they flew to forage on grass fields.
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de Waal, F. B. M., & Luttrell, L. M. (1988). Mechanisms of social reciprocity in three primate species: Symmetrical relationship characteristics or cognition? Ethology and Sociobiology, 9(2–4), 101–118.
Abstract: Agonistic intervention behavior was observed in captive groups of chimpanzees (Pan troglodytes), rhesus monkeys (Macaca mulatta), and stumptail monkeys (M. arctoides). Reciprocity correlations of interventions were determined while removing from the data the effects of several symmetrical relationship characteristics, that is, matrillineal kinship, proximity relations, and same-sex combination. It was considered likely that if significant reciprocity persisted after controlling for these characteristics, the reciprocity was based on cognitive mechanisms. Statistical significance was tested by means of recently developed matrix permutation procedures. All three species exhibited significant reciprocity with regard to beneficial interventions, even after controlling for symmetrical traits. Harmful interventions were, however, reciprocal among chimpanzees only. This species showed a “revenge system”, that is, if A often intervened against B, B did the same to A. In contrast, both macaque species showed significantly inversed reciprocity in their harmful interventions: if A often intervened against B, B rarely intervened against A. Further analysis indicates that the strict hierarchy of macaques prevents them from achieving complete reciprocity. Compared to chimpanzees, macaques rarely intervene against higher ranking group members. The observed contrast can be partially explained on the basis of differences in available space, as indicated by a comparison of indoor and outdoor living conditions for the chimpanzee colony. Yet, even when such spatial factors are taken into account, substantial behavior differences between chimpanzees and macaques remain.
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Rutberg, A. T. (1987). Horse Fly Harassment and the Social Behavior of Feral Ponies. Ethology, 75(2), 145–154.
Abstract: Abstract Horse flies (Tabanidae) on and around feral ponies in harem groups were counted at Assateague Island National Seashore, Maryland, U.S.A., between June and August 1985. Harem stallions attracted the most flies; adult mares showed intermediate fly numbers, while few flies landed on foals under any circumstances. The use of thermal and chemical cues by flies selecting a host may have helped create this disparity. When flies were abundant, ponies reduced spacing within the group. Ponies in larger groups suffered from fewer flies than ponies in smaller groups. There was, however, no evidence that ponies merged into larger groups in response to fly harassment, suggesting that biting flies play little role in structuring pony social organization.
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