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Shanghai, China

Ren B.,CAS Institute of Zoology | Li D.,CAS Institute of Zoology | Li D.,China West Normal University | He X.,Shanghai Wild Animal Park | And 2 more authors.
PLoS ONE | Year: 2011

Background: Infanticide by adult male occurs in many mammalian species under natural conditions, and it is often assumed to be a goal-directed action and explained predominately by sexual selection. Motivation of this behavior in mammals is limitedly involved. Methodology and Principal Findings: We used long-term reproductive records and direct observation in captivity and in the field of two snub-nosed langur species on the basis of individual identification to investigate how infanticide happened and to be avoided in nonhuman primates. Our observations suggested that infanticide by invading males might be more accidental than goal-directed. The invading male seemed to monopolize all the females including lactating mothers during takeovers. Multiparous mothers who accepted the invading male shortly after takeovers avoided infanticide in most cases. Our results conjectured primiparous mothers would decrease infanticidal possibility if they sexually accepted the invading male during or immediately after takeovers. In the studied langur species, voluntary abortion or mating with the invading male was evidently adopted by females to limit or avoid infanticide by takeover males. Conclusions and Significance: The objective of the invading male was to monopolize all adult females after his takeover. It appeared that the mother's resistance to accepting the new male as a mating partner was the primary incentive for infanticide. Motivation analysis might be helpful to further understand why infanticide occurs in primate species. © 2011 Ren et al.

Ren R.-M.,Peking University | Yan K.-H.,Peking University | Su Y.-J.,Peking University | Xia S.-Z.,Shanghai Wild Animal Park | And 3 more authors.
Zoological Studies | Year: 2010

Detailed accounts of social relationships in the golden snub-nosed langur Rhinopithecus roxellana are rare, and little is know about its social structure. The aim of this study was to contribute to the understanding of social relationships by analyzing patterns of affiliative and aggressive interactions in a captive group of this poorly known species. The 11 focal individuals were organized into a one-male unit, or OMU (i.e., a single adult male that associates with multiple adult females and their offspring), and an all-male unit, or AMU (i.e., a social unit formed only by males). One-minute instantaneous scans and ad libitum sampling techniques were used to record affiliative and agonistic behaviors, respectively. In general, OMU and AMU individuals displayed similar amounts of affiliative behaviors. However, affiliative interactions were more frequent within than between subunits. On the other hand, AMU members displayed more aggression towards members of their own subunit, and more often counterattacked any group member than did individuals of the OMU. Although OMU and AMU individuals did not interchange more agonistic behaviors with members of their own subunit than with members of the other subunit, they intervened more often on behalf of members of their own subunit, and against individuals of the other subunit. We discuss our results in the context of what is known regarding social behavior in captive and wild populations of this species and other primates with a multilevel social system.

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