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Boesch C, & Boesch H. (1984). Mental maps in wild chimpanzees: an analysis of hammer transports for nut cracking. Primates, 25, 160.
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Yamakoshi G, & Sugiyama Y. (1995). Pestle-pounding behavior of wild chimpanzees at Bossou, Guinea: a newly observed tool-using behavior. Primates, 36, 489.
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Cordeiro de Sousa, M., Xavier, N., Alves da Silva, H., Souza de Oliveira, M., & Yamamoto, M. (2001). Hand preference study in marmosets ( Callithrix jacchus ) using food reaching tests. Primates, 42(1), 57–66.
Abstract: Abstract Hand preference has been investigated in New World primates but the data obtained thus far are controversial. In this study we investigated hand preference in common marmosets,Callithrix jacchus, during the execution of a reaching for food task. We used 46 adult common marmoset males (n=27) and females (n=19) from the Universidade of Rio Grande do Norte colony, both wild and captive-born. To test the hand preference we used a device measuring 10 cm2, with a central hole 1 cm in diameter, to force the animal to use only one hand to reach for food on a food dish located underneath. Each animal was tested 5 times and had to make a maximum of 20 successful attempts per session. A total of 100 successful attempts per animal and 4,600 successful attempts for all animals were recorded during the experiment. Latency and duration of the sessions were measured and we found preference for the use of one of the hands in common marmoset individuals, i.e. 45 of total of 46 animals used significantly more the right or the left hand when performing the task. However no bias at the population level was found. Females born in captivity presented an increase in the duration of latency for the first successful attempt and in the total duration of the test sessions. These findings might be indicating differences associated with a natural tendency for females to be more selective and to spend more time exploring alimentary sources. Additionally, captive-born females may have a constrain in developing cognitive abilities regarding foraging since they have food available during most part of the time.
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Brennan, J., & Anderson, J. (1988). Varying responses to feeding competition in a group of rhesus monkeys (Macaca mulatta). Primates, 29(3), 353–360.
Abstract: The behaviour of members of a group of rhesus monkeys was observed in experimentally created, competitive feeding situations. Socially dominant members of the group tended to start eating before lower-ranking subjects, and generally ate more. Dominants sometimes used aggression to control access to food, but overall, intermediate-ranking monkeys were involved in most agonistic episodes. Non-dominant subjects improved their feeding performance when food was presented in three piles rather than one pile, often by snatching food and consuming it away from the pile. These general patterns were less evident when realistic snake models were placed on some of the food piles. Feeding was disrupted by the presence of snakes, but notably, subordinates risked feeding in these conditions. Piles containing preferred foods and snakes were eaten from, but a low-preference food (carrot) under snakes went untouched by all subjects. The results suggest that group-members evaluate potential risks and benefits of competing for a restricted resource, and that dominance status, while an important factor, is only one element in the equation.
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Neville, M. K. (1968). Male leadership change in a free-ranging troop of Indian rhesus monkeys (Macaca mulatta). Primates, 9(1), 13–27.
Abstract: The male leadership of a troop of rhesus living at the foot of the Kumaon foothills of India was studied from January to December of 1965. The troop, inhabiting a region of fields and forests, varied in size from a maximum of 20 after the birth season to a minimum of 14 in December during the breeding season. The troop initially contained two adult males with the occasional presence of a third, more peripheral male. This third male disappeared in March and was perhaps identical with the male who began to appear in August and succeeded in displacing the dominant male from the troop. The second initial male succeeded to the dominant position in September. During the breeding season various extra-troop males followed and occasionally penetrated the troop. The second male had difficulty in maintaining his position against one of these, who had perhaps been the peripheral male at the beginning of 1965.
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Mori, A., Iwamoto, T., & Bekele, A. (1997). A case of infanticide in a recently found gelada population in Arsi, Ethiopia. Primates, 38(1), 79–88.
Abstract: Abstract There have been no reports of infanticide in wild gelada baboons and it has been argued that infanticide is not necessary in geladas, since the birth interval of female gelada can be shortened after takeover of a unit by a new leader male without infanticide. However, we observed an instance of infanticide in a newly-found wild gelada population in the Arsi Region of Ethiopia. After a leader male of the unit was severely wounded by a leopard attack, he was quite weakened. The second male of the unit, a young adult male, became the leader of the unit three weeks later, but the former leader continued to stay in the unit as a second male. After a week, two other adult males joined the unit which, therefore, came to include four adult males. The infanticide took place nine days later. The perpetrator was one of the immigrant males and he showed great interest in the mother of the unweaned victim infant. Although the perpetrator copulated with her after the infanticide, the usurper was found to own all three adult females after two weeks following the infanticide; i.e. the perpetrator could not own any female. The wounded former leader showed conspicuous protective behavior towards the victim's mother and the dead infant. One possible explanation for the occurrence of infanticide in this population of geladas is as follows. Gelada males in this area may be able to join units more easily to form multi-male units but then have shorter tenure in the units. Facing the unstable condition of units, they may sometimes engage in infanticide to increase their breeding opportunities, even before becoming a leader.
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Dunbar, R. I. M. (1974). Observations on the ecology and social organization of the green monkey,Cercopithecus sabaeus, in Senegal. Primates, 15(4), 341–350.
Abstract: The green monkey,Cercopithecus sabaeus, has not been studied in its natural habitat in West Africa. This paper reports observations made during a 3-month study in Senegal. Green monkeys live in multimale groups averaging some 12 individuals. Information is given on home range size, use of habitat, daily activity patterns, diet and birth seasonality. Social organization is discussed and data are given on the relationships between age-sex classes, aggression and leadership. Inter-group relations are discussed and it is suggested that groups defend their ranges as territories. The ecology and social organization of green monkeys is compared with that of populations ofC. aethiops studied in East Africa and they are found to be similar.
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Southwick, C. H., & Siddiqi, M. R. (1967). The role of social tradition in the maintenance of dominance in a wild rhesus group. Primates, 8(4), 341–353.
Abstract: Following the injury and disability of the dominant male, the home range of a group of rhesus in a rural habitat in Aligarh district was significantly reduced from 40 acres to less than 10 acres. Throughout this injury and prior to his death, the male maintained his dominance in reference to a peripheral male who frequently attempted to enter the group. Upon the death of the dominant male, group leadership and dominance was assumed by a young subdominant male within the group and the peripheral male still remained outside the group. These observations indicate a strong social tradition in the maintenance of dominance within this wild rhesus group, and they emphasize the role of the dominant male in maintaining home range.
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Bunnell, B., & Perkins, M. (1980). Performance correlates of social behavior and organization: Social rank and complex problem solving in crab-eating macaques (M. fascicularis). Primates, 21(4), 515–523.
Abstract: Abstract Seventeen male crab-eating macaques, drawn from two captive troops, were tested on a series of complex problem solving tasks in a Wisconsin General Test Apparatus (wgta). The animals were trained on a series of 6-trial object quality learning set problems followed by a series of 10-trial object quality learning set problems. They were then given problems in which the correct stimulus object was reversed part way through the problem. After the animals reached criterion on this task, the reversal learning set was then extinguished. High ranking animals made more intraproblem errors than low ranking animals on the 6-trial problems, but there was no relationship between social status and the rapidity with which the object quality learning set was established. Animals that received overtraining on the 6-trial problems transferred their learning virtually intact to the 10-trial problems; however, high ranking animals without overtraining made more errors than low ranking animals. On reversal learning and reversal extinction, high ranking animals made more errors on critical trials, indicating that they formed and extinguished the reversal set more slowly than low ranking animals. Object quality sets, as measured by trial-2 performance, were not affected by the reversal conditions.
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Bunnell, B., Gore, W., & Perkins, M. (1980). Performance correlates of social behavior and organization: Social rank and reversal learning in crab-eating macaques (M. fascicularis). Primates, 21(3), 376–388.
Abstract: Abstract Seventeen male crab-eating macaques drawn from two captive troops, were tested on a brightness discrimination, reversal learning task. Fourteen of these animals completed ten reversals. It was found that the performance of the three highest ranking animals from each troop, taken together, was poorer than that of the lower ranking animals that were tested. The high ranking animals made more errors before reaching criterion on both initial learning and the reversal problems. Analysis of error patterns revealed that, while the high ranking animals had no more difficulty than the others in withholding their responses to the previously correct stimulus following reversals, they did not adopt the correct strategy as soon as the low ranking animals. The results have been interpreted in terms of a carry-over of a hypothetical factor or factors resulting from pressures created by the ongoing social dynamics involved in establishing and maintaining a given social rank at the time laboratory testing occurred.
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