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Kerhoas D.,Max Planck Institute for Evolutionary Anthropology | Kerhoas D.,University of Leipzig | Kerhoas D.,Jr Research Group Of Primate Sexual Selection | Kerhoas D.,University of Gottingen | And 8 more authors.
Behavioral Ecology and Sociobiology | Year: 2016

Abstract: In promiscuous primates, interactions between adult males and infants have rarely been investigated. However, recent evidence suggests that male affiliation towards infants has an influence on several aspects of the infants’ life. Furthermore, affiliations may be associated with male reproductive strategy. In this study, we examined which social factors influenced male-infant affiliation initiated by either male or infant, in wild crested macaques (Macaca nigra). We combined behavioral data and genetic paternity analysis from 30 infants living in three wild groups in Tangkoko Reserve, Indonesia. Our results indicate that adult males and infants do not interact at random, but rather form preferential associations. The social factors with the highest influence on infant-initiated interactions were male rank and male association with the infant’s mother. While infants initiated affiliations with males more often in the absence of their mothers, adult males initiated more affiliations with infants when their mothers were present. Furthermore, males initiated affiliations more often when they were in the same group at the time the infant was conceived, when they held a high dominance rank, or when they had a close relationship with the mother. Interestingly, paternity did not affect male-infant affiliation despite being highly skewed in this species. Overall, our results suggest that adult males potentially associate with an infant to secure future mating with the mother. Infants are more likely to associate with a male to receive better support, suggesting a strategy to increase the chance of infant survival in a primate society with high infant mortality. Significance statement: We explore social relationships between males and infants in a promiscuous primate, the wild crested macaque. Our novel approach addresses the nature of affiliations both from males’ and infants’ perspectives. The results show that males and infants form preferential associations. Male-female affiliation, but not paternity, was a significant predictor of interactions initiated both by males and infants. Males initiated more interactions towards infants when the mother was in proximity, while infants initiated more interactions in her absence. Finally, high-ranking males were more likely to initiate interactions towards infants. We demonstrated that paternity is not a good predictor of male-infant affiliations, even in a species with a high reproductive skew and a relatively high confidence of paternity. Our paper is one of the first to show that infants are active agents in establishing and maintaining preferential relationships with males. © 2016 The Author(s)

Engelhardt A.,Jr Research Group Of Primate Sexual Selection | Engelhardt A.,Free University of Berlin | Fischer J.,Research Group Cognitive Ethology | Neumann C.,Jr Research Group Of Primate Sexual Selection | And 2 more authors.
Behavioral Ecology and Sociobiology | Year: 2012

Primates are unusual in that many females display sexual signals, such as sex skin swellings/colorations and copulation calls, without any sex role reversal. The adaptive function of these signals remains largely unclear, although it has been suggested that they provide males with information on female reproductive status. For sex skin swellings, there is increasing evidence that they represent a graded signal indicating the probability of ovulation. Data on the functional significance of copulation calls are much scarcer. To clarify the information content of such calls, we recorded copulation calls in wild long-tailed macaques (Macaca fascicularis) and analysed the structure of these calls during the ovarian cycle. Specifically, we correlated selected call parameters with the female oestrogen to progestogen ratio (obtained from faecal samples), which are known to be elevated during the female's fertile phase. In addition, we ran a general linear mixed model for these call parameters, testing factors (cycle phase, occurrence/absence of ejaculation, male dominance status, occurrence/absence of mate guarding) which potentially influence female copulation calls in primates. Our results show that copulation calls of female long-tailed macaques signal mating outcome and rank of the mating partner, but not female reproductive status. They also show for the first time on primates that copulation calls can convey information on whether a female is mate guarded or not. We suspect that the function of these calls is manipulation of male mating and mate-guarding behaviour and that in this way the degree of sperm competition and ultimately male reproductive success is influenced. © 2011 The Author(s).

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