Baker, K. C., Seres, E., Aureli, F., & De Waal, F. B. (2000). Injury risks among chimpanzees in three housing conditions. Am. J. Primatol., 51(3), 161–175.
Abstract: Meeting the psychological needs of chimpanzees (Pan troglodytes) can be a challenge given their aggressiveness on the one hand and the complexity of their social lives on the other. It is unclear how to balance the need to provide opportunities for species-appropriate behavior against potential risks of injury chimpanzees may inflict on each other. This study evaluates the suggestion that simpler social environments protect chimpanzees from wounding. Over a two-year period all visible injuries to 46 adult males, 64 adult females, and 25 immature chimpanzees were recorded at the Yerkes Regional Primate Research Center. Approximately half of the subjects were mother-reared, and the rest were nursery-reared. Housing included compounds containing about 20 chimpanzees, interconnected indoor-outdoor runs for groups of up to 12 individuals, and smaller indoor-outdoor runs for pairs and trios. Annual wounding rates were calculated for serious wounds (extensive injuries and all those requiring veterinary intervention) as well as for minor wounds. Compound-housed chimpanzees incurred the highest level of minor wounding, but serious wounding levels were not affected by housing condition. Even with a period of dominance instability and elevated levels of wounding in one compound, compound chimpanzees were not injured more than those in smaller social groups over the long term. Nursery-reared females in moderate-sized groups were wounded more than mother-reared females. Also, nursery-reared males and females were wounded less often when paired with mother-reared companions. Overall, this study indicates that maintaining chimpanzees in pairs and trios would not be an effective means for reducing injuries. The management of wounding in chimpanzee colonies is influenced more by the sex and rearing composition of a colony.
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Parish, A. R., & De Waal, F. B. (2000). The other “closest living relative”. How bonobos (Pan paniscus) challenge traditional assumptions about females, dominance, intra- and intersexual interactions, and hominid evolution. Ann N Y Acad Sci, 907, 97–113.
Abstract: Chimpanzee (Pan troglodytes) societies are typically characterized as physically aggressive, male-bonded and male-dominated. Their close relatives, the bonobos (Pan paniscus), differ in startling and significant ways. For instance, female bonobos bond with one another, form coalitions, and dominate males. A pattern of reluctance to consider, let alone acknowledge, female dominance in bonobos exists, however. Because both species are equally “man's” closest relative, the bonobo social system complicates models of human evolution that have historically been based upon referents that are male and chimpanzee-like. The bonobo evidence suggests that models of human evolution must be reformulated such that they also accommodate: real and meaningful female bonds; the possibility of systematic female dominance over males; female mating strategies which encompass extra-group paternities; hunting and meat distribution by females; the importance of the sharing of plant foods; affinitive inter-community interactions; males that do not stalk and attack and are not territorial; and flexible social relationships in which philopatry does not necessarily predict bonding pattern.
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de Waal, F. B., & Berger, M. L. (2000). Payment for labour in monkeys. Nature, 404(6778), 563.
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Parr, L. A., Winslow, J. T., Hopkins, W. D., & de Waal, F. B. (2000). Recognizing facial cues: individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). J Comp Psychol, 114(1), 47–60.
Abstract: Faces are one of the most salient classes of stimuli involved in social communication. Three experiments compared face-recognition abilities in chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). In the face-matching task, the chimpanzees matched identical photographs of conspecifics' faces on Trial 1, and the rhesus monkeys did the same after 4 generalization trials. In the individual-recognition task, the chimpanzees matched 2 different photographs of the same individual after 2 trials, and the rhesus monkeys generalized in fewer than 6 trials. The feature-masking task showed that the eyes were the most important cue for individual recognition. Thus, chimpanzees and rhesus monkeys are able to use facial cues to discriminate unfamiliar conspecifics. Although the rhesus monkeys required many trials to learn the tasks, this is not evidence that faces are not as important social stimuli for them as for the chimpanzees.
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de Waal, F. B. (1999). The end of nature versus nurture. Sci Am, 281(6), 94–99.
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Lilienfeld, S. O., Gershon, J., Duke, M., Marino, L., & de Waal, F. B. (1999). A preliminary investigation of the construct of psychopathic personality (psychopathy) in chimpanzees (Pan troglodytes). J Comp Psychol, 113(4), 365–375.
Abstract: Although the construct of psychopathy has received considerable attention in humans, its relevance to other animals is largely unknown. We developed a measure of psychopathy for use in chimpanzees (Pan troglodytes), the Chimpanzee Psychopathy Measure (CPM), and asked 6 raters to complete this index on 34 chimpanzees. The CPM (a) demonstrated satisfactory interrater reliability and internal consistency; (b) exhibited marginally significant sex differences (males > females); (c) correlated positively with measures of extraversion, agreeableness, and observational ratings of agonism, sexual activity, daring behaviors, teasing, silent bluff displays, and temper tantrums, and negatively with observational ratings of generosity; and (d) demonstrated incremental validity above and beyond a measure of dominance. Although further validation of the CPM is needed, these findings suggest that the psychopathy construct may be relevant to chimpanzees.
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Call, J., Aureli, F., & de Waal, F. B. M. (1999). Reconciliation patterns among stumptailed macaques: a multivariate approach. Anim. Behav., 58(1), 165–172.
Abstract: This study focused on two aspects of the dynamics of reconciliation in stumptailed macaques, Macaca arctoides. First, we investigated the combined effects of multiple variables (i.e. sex, age, rank, conflict intensity, outcome, or number of participants, interopponent distance, kinship and friendship) on the occurrence of reconciliation. Second, we investigated whether opponents used different behaviour patterns in their postconflict reunions depending on the characteristics of their conflicts or their relationship with their opponents. We studied a multimale, multifemale group of 38 stumptailed macaques housed in a large outdoor compound. Three types of data were collected: (1) instantaneous scan sampling of contact sitting to infer 'friendship'; (2) ad libitum data on bared-teeth and teeth-chattering displays to infer dominance rank; (3) 10-min focal observations during postconflict (PC) and matched control (MC) periods in which we recorded interopponent distance at the beginning of the observation and all aggressive and affiliative behaviours between former opponents. Our study confirmed the high conciliatory tendency of stumptailed macaques previously reported for other groups. A stepwise logistic regression revealed that initial interopponent distance in PC, friendship and kinship were the only factors that independently contributed to explain the occurrence of reconciliation. Two main clusters of postconflict behavioural patterns emerged: allogrooming+contact sitting and sociosexual behaviours (e.g. hold-bottom). It is hypothesized that postconflict allogrooming and contact sitting may be used for the maintenance of valuable relationships, whereas sociosexual behaviours may be used more indiscriminately by any pair of opponents as a buffering mechanism to prevent immediate recurrence of aggression. Copyright 1999 The Association for the Study of Animal Behaviour.
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Parr, L. A., & de Waal, F. B. (1999). Visual kin recognition in chimpanzees (Vol. 399).
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de Waal, F. B. (1999). Cultural primatology comes of age. Nature, 399(6737), 635–636.
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Aureli, F., Preston, S. D., & de Waal, F. B. (1999). Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): a pilot study. J Comp Psychol, 113(1), 59–65.
Abstract: Heart rate telemetry was explored as a means to access animal emotion during social interactions under naturalistic conditions. Heart rates of 2 middle-ranking adult females living in a large group of rhesus macaques (Macaca mulatta) were recorded along with their behavior. Heart rate changes during 2 types of interactions were investigated, while controlling for the effects of posture and activity. The risk of aggression associated with the approach of a dominant individual was expected to provoke anxiety in the approachee. This prediction was supported by the heart rate increase after such an approach. No increase was found when the approacher was a kin or a subordinate individual. The tension-reduction function of allogrooming was also supported. Heart rate decelerated faster during the receipt of grooming than in matched control periods.
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