During 12 years of observation, we have observed three confirmed and two inferred lethal coalitio... more During 12 years of observation, we have observed three confirmed and two inferred lethal coalitionary attacks on adult male white-faced capuchins (Cebus capucinus) by members of two habituated social groups at Lomas Barbudal Biological Reserve, Costa Rica. In one case, an alpha male was badly wounded and evicted from his group, and when later found by his former groupmates he was attacked by several of them and died less than 24 h later. In two other cases, lone extra-group males were mobbed by adult and immature males of a bisexual group. One victim's abdomen was torn open and he died less than 24 h later. A second victim was quite badly bitten but may have escaped. The fourth and fifth cases resulted from intergroup encounters. One victim lost the use of both arms but may have survived, whereas the other died of unknown causes within an hour of the attack. The observed death rate from coalitionary aggression at our site is approximately the same as that reported for eastern chimpanzees. Because at least three of the five observed incidents involved large coalitions attacking lone victims, they support the general hypothesis that imbalances of power contribute to intraspecific killing in primates. However, the occurrence of lethal coalitional attacks in a species lacking fission-fusion social organization poses a challenge to the more specific version of the imbalance-of-power hypothesis proposed by Manson and Wrangham in 1991 to explain chimpanzee and human intergroup aggression.
Research on nonhuman primate personality dimensions has focused on a small number of taxa, and li... more Research on nonhuman primate personality dimensions has focused on a small number of taxa, and little of this work has focused on wild populations. We used ratings to assess personality structure in wild white-faced capuchins (Cebus capucinus) over a 9-year period, using a capuchin-specific rating instrument based partly on existing instruments. Adequate levels of interrater reliability were found for 24 of 26 items. A longitudinal analysis found that 15 of these items showed significant rank-order stability from adolescence through early adulthood. Principal components analysis revealed 5 components. Four of these components were recognizable "Big Five" dimensions: Extraversion (E), Openness (O), Neuroticism (N), and Agreeableness (A). A dimension incorporating aspects of high O and high Conscientiousness (C) was labeled Eccentricity. Every dimension except for N showed significant rank-order stability from adolescence through early adulthood. Males were more extraverted, open, neurotic, and eccentric than females, whereas females were more agreeable than males. A cross-sectional analysis revealed that openness and agreeableness declined, whereas eccentricity increased, during adulthood. The item content of capuchin Extraversion and Openness, and the existence of a distinctive Eccentricity dimension, are consistent with known characteristics of capuchin social and ecological adaptations, specifically the central roles of alliances, behavioral innovation, and social learning.
The parcelling model of reciprocity predicts that grooming partners will alternate between giving... more The parcelling model of reciprocity predicts that grooming partners will alternate between giving and receiving grooming within grooming bouts, and that each partner will perform approximately as much grooming as it receives within each bout ('time matching'). Models of allogrooming based on biological markets theory predict that individuals of lower dominance rank will exchange grooming for tolerance from high-rankers, and therefore an inverse relation will be found between grooming partners' dominance rank distance and how closely they match each other's grooming contributions within each bout. We used weighted logistic regression and weighted least-squares regression to test these predictions using data from female white-faced capuchins, Cebus capucinus, and bonnet macaques, Macaca radiata. Only 5e7% of macaque grooming bouts, and 12e27% of capuchin grooming bouts, were reciprocated. However, (1) the duration of grooming by the first groomer significantly predicted whether the groomee would reciprocate at all, and (2) when bouts were reciprocated, the duration of grooming by the first groomer significantly predicted the duration of grooming by the second groomer. Grooming was most balanced among females of similar dominance ranks. Both the time-matching and rank-related effects were weak, although significant. These results indicate that although some form of time matching may be a general characteristic of grooming in female-bonded primate species, time matching accounts for relatively little of the variation in the distribution of grooming within bouts. We also draw attention to weighted regression as a technique that avoids pseudoreplication while using all available data.
Whether nonhuman primates avoid copulating with close kin living in their social group is controv... more Whether nonhuman primates avoid copulating with close kin living in their social group is controversial. If sexual aversion to relatives occurs, it should be stronger in females than in males because of females' greater investment in each offspring and hence greater costs resulting from less viable offspring. Data presented here show that adult male rhesus macaques breeding in their natal groups at Cay0 Santiago experienced high copulatory success, but copulated less with females of their own matrilineages than with females of other matrilineages. Adult females were never observed to copulate with males of their own matrilineage during their fertile periods. Although natal males sometimes courted their relatives, examination of two measures of female mate choice showed that females chose unrelated natal males over male kin. Female aversion to male kin was specific to the sexual context; during the birth season, females did not discriminate against their male relatives in distributing grooming. Evolved inbreeding avoidance mechanisms probably produce different outcomes at Cay0 Santiago than in wild rhesus macaque populations. Gender differences in sexual aversion to relatives may be partly responsible for differences between studies in reported frequency of copulations by related pairs. o 1993 Wiley-Liss, Inc.
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During 12 years of observation, we have observed three confirmed and two inferred lethal coalitio... more During 12 years of observation, we have observed three confirmed and two inferred lethal coalitionary attacks on adult male white-faced capuchins (Cebus capucinus) by members of two habituated social groups at Lomas Barbudal Biological Reserve, Costa Rica. In one case, an alpha male was badly wounded and evicted from his group, and when later found by his former groupmates he was attacked by several of them and died less than 24 h later. In two other cases, lone extra-group males were mobbed by adult and immature males of a bisexual group. One victim's abdomen was torn open and he died less than 24 h later. A second victim was quite badly bitten but may have escaped. The fourth and fifth cases resulted from intergroup encounters. One victim lost the use of both arms but may have survived, whereas the other died of unknown causes within an hour of the attack. The observed death rate from coalitionary aggression at our site is approximately the same as that reported for eastern chimpanzees. Because at least three of the five observed incidents involved large coalitions attacking lone victims, they support the general hypothesis that imbalances of power contribute to intraspecific killing in primates. However, the occurrence of lethal coalitional attacks in a species lacking fission-fusion social organization poses a challenge to the more specific version of the imbalance-of-power hypothesis proposed by Manson and Wrangham in 1991 to explain chimpanzee and human intergroup aggression.
Research on nonhuman primate personality dimensions has focused on a small number of taxa, and li... more Research on nonhuman primate personality dimensions has focused on a small number of taxa, and little of this work has focused on wild populations. We used ratings to assess personality structure in wild white-faced capuchins (Cebus capucinus) over a 9-year period, using a capuchin-specific rating instrument based partly on existing instruments. Adequate levels of interrater reliability were found for 24 of 26 items. A longitudinal analysis found that 15 of these items showed significant rank-order stability from adolescence through early adulthood. Principal components analysis revealed 5 components. Four of these components were recognizable "Big Five" dimensions: Extraversion (E), Openness (O), Neuroticism (N), and Agreeableness (A). A dimension incorporating aspects of high O and high Conscientiousness (C) was labeled Eccentricity. Every dimension except for N showed significant rank-order stability from adolescence through early adulthood. Males were more extraverted, open, neurotic, and eccentric than females, whereas females were more agreeable than males. A cross-sectional analysis revealed that openness and agreeableness declined, whereas eccentricity increased, during adulthood. The item content of capuchin Extraversion and Openness, and the existence of a distinctive Eccentricity dimension, are consistent with known characteristics of capuchin social and ecological adaptations, specifically the central roles of alliances, behavioral innovation, and social learning.
The parcelling model of reciprocity predicts that grooming partners will alternate between giving... more The parcelling model of reciprocity predicts that grooming partners will alternate between giving and receiving grooming within grooming bouts, and that each partner will perform approximately as much grooming as it receives within each bout ('time matching'). Models of allogrooming based on biological markets theory predict that individuals of lower dominance rank will exchange grooming for tolerance from high-rankers, and therefore an inverse relation will be found between grooming partners' dominance rank distance and how closely they match each other's grooming contributions within each bout. We used weighted logistic regression and weighted least-squares regression to test these predictions using data from female white-faced capuchins, Cebus capucinus, and bonnet macaques, Macaca radiata. Only 5e7% of macaque grooming bouts, and 12e27% of capuchin grooming bouts, were reciprocated. However, (1) the duration of grooming by the first groomer significantly predicted whether the groomee would reciprocate at all, and (2) when bouts were reciprocated, the duration of grooming by the first groomer significantly predicted the duration of grooming by the second groomer. Grooming was most balanced among females of similar dominance ranks. Both the time-matching and rank-related effects were weak, although significant. These results indicate that although some form of time matching may be a general characteristic of grooming in female-bonded primate species, time matching accounts for relatively little of the variation in the distribution of grooming within bouts. We also draw attention to weighted regression as a technique that avoids pseudoreplication while using all available data.
Whether nonhuman primates avoid copulating with close kin living in their social group is controv... more Whether nonhuman primates avoid copulating with close kin living in their social group is controversial. If sexual aversion to relatives occurs, it should be stronger in females than in males because of females' greater investment in each offspring and hence greater costs resulting from less viable offspring. Data presented here show that adult male rhesus macaques breeding in their natal groups at Cay0 Santiago experienced high copulatory success, but copulated less with females of their own matrilineages than with females of other matrilineages. Adult females were never observed to copulate with males of their own matrilineage during their fertile periods. Although natal males sometimes courted their relatives, examination of two measures of female mate choice showed that females chose unrelated natal males over male kin. Female aversion to male kin was specific to the sexual context; during the birth season, females did not discriminate against their male relatives in distributing grooming. Evolved inbreeding avoidance mechanisms probably produce different outcomes at Cay0 Santiago than in wild rhesus macaque populations. Gender differences in sexual aversion to relatives may be partly responsible for differences between studies in reported frequency of copulations by related pairs. o 1993 Wiley-Liss, Inc.
APA PsycNET Our Apologies! - The following features are not available with your current Browser c... more APA PsycNET Our Apologies! - The following features are not available with your current Browser configuration. - alerts user that their session is about to expire - display, print, save, export, and email selected records - get My ...
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