Social factors affecting reproductive success in female gelada baboons (Theropithecus gelada).
Item
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Title
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Social factors affecting reproductive success in female gelada baboons (Theropithecus gelada).
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Identifier
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AAI9605630
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identifier
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9605630
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Creator
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McCann, Colleen Marie.
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Contributor
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Adviser: John F. Oates
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Date
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1995
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Language
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English
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Publisher
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City University of New York.
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Subject
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Anthropology, Physical | Biology, Animal Physiology
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Abstract
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A knowledge of variation in female reproductive success and of the factors responsible for such variation is essential for a full understanding of the evolution of primate life-history strategies, including social behavior. Inter-individual variation in female fertility has been observed in several primate species; and in some, evidence of a positive correlation between a female's dominance rank and her fertility has suggested that increased fertility is a corollary of the advantages accrued by dominant individuals (Harcourt, 1987; Dunbar, 1988; Abbott, 1991). In wild gelada baboons (Theropithecus gelada), low-ranking females raise offspring less frequently than do high-ranking females. In discussing the results of his long-term field studies, Dunbar (1989) has suggested that reproductive suppression in low-ranking females, as a consequence of social stress, is a significant factor contributing to the variation in birth rates of individual females.;In the present study, I investigated whether ovarian suppression resulting from social stress contributed to the reproductive impairment of low-ranking females. This question was investigated in semi-free-ranging groups of gelada baboons maintained at the Wildlife Conservation Society's Bronx Zoo. Observational sampling was combined with the laboratory analysis of hormones in samples of urine collected from individual females.;The main findings of this study were that a female's dominance rank can have important consequences for her relationship with other females and the unit male, and ultimately for her reproductive success. Low-ranking females experienced lower copulation frequencies and higher rates of aggression and cortisol secretion, which increased significantly during the follicular phase of the menstrual cycle. The interval between ovulations was greater for low-ranking females than it was for high-ranking females, and the increased length of the menstrual cycle was due to an elongation of the follicular phase.;The data suggest that harassment of low-ranking female gelada baboons by high-ranking females may have resulted in lengthened menstrual cycles and reduced ovulatory frequency in low-ranking females. Reduced ovulatory frequency may lead to the delay in conceptions in low-ranking females found in wild populations. High-ranking female gelada baboons may be imposing stress-induced suppression of reproduction on their female subordinates to obtain a reproductive advantage.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
