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The Cape ground squirrel, Xerus inauris, is a highly social cooperative breeder that forms groups containing multiple breeding females. While the distribution of reproduction among group members is fairly even (i.e. exhibits low reproductive skew), previous studies of Cape ground squirrels suggest the reproductive development of sub-adult females is inhibited by the presence of adult breeding female group mates. As reproductive delay is known to be influenced by a number of different parameters, my goal was to determine if other factors affected the timing of sexual maturity, and if so, which factors are the most influential. In this study, I simultaneously test the relative power of seven different social and environmental parameters at explaining the variation in the female age of sexual maturity in two populations of Cape ground squirrels. Field work was conducted at two study sites in southern Africa, where trapping, behavioral and hormonal data were collected to determine the timing of reproductive development. Hormonal data was analyzed through the use of steroid enzyme immunoassay analysis to quantify the concentration of gonadal hormone in fecal samples which indicate the onset of sexual maturity. Prior to the start of the field season, I conducted an initial experiment to determine the best alternative form of fecal storage if freezing was unavailable. I found that drying feces provides a more reliable method for long-term preservation of fecal steroid concentrations when compared to storing fecal samples in alcohol. Data associated with each of the seven parameters was analyzed using model selection to simultaneously measure the ability of different combinations of parameters to explain the observed variation in female age of sexual maturity. I found that an increase in the number of adult breeding female group mates and related adult male group mates resulted in a substantial inhibition of female reproductive maturity. I concluded that a female Cape ground squirrel's age of sexual maturity is principally a result of the interaction between adult breeding females' capacity for reproductive suppression and sub-adults' ability to maximize lifetime reproductive success while minimizing inbreeding. The overall reproductive dynamics of each social group results from the tug-of-war between the adult and sub-adult female group mates to control breeding within the group, with minimal direct influence on sexual maturity by environmental factors.

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Thesis (M.Sc.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 101-113. Also available online.

Call number: LD2668 .T4 1963 G42 / Master of Science

Thesis (MSc (Biochemistry))--University of Stellenbosch, 2004. / This study describes: 1. Investigation of product inhibition regarding the metabolism of progesterone in ovine adrenal micosomes. 2. The employment of novel cell culture techniques to study the effect of CYP17 and CYP21 concentration on adrenal progesterone metabolism. 3. The formulation of a mathematical model describing the behaviour of the observed results in point 2.