My dissertation focuses on understanding the mechanisms underpinning growth, reproduction, and survival in the spotted hyena. Following a general introductory chapter, my dissertation is composed of four independent research chapters. I begin with Chapter 2 in which my colleagues and I document a positive linear relationship between social dominance rank and telomere length. We also report significant variability in telomere length of high-ranking females among different social groups, suggesting that both social dominance rank and group membership influence this important biomarker of aging. In Chapter 3, we describe the role of juvenile concentrations of the hormone, insulin-like growth-factor -1 (IGF-1), in predicting trade-offs between early-life growth and later-life reproduction and survival among female hyenas. In Chapter 4, I explore IGF-1 as a potential mechanism of female-biased sexual size dimorphism by documenting sex-biased concentrations, sensitivities, and adaptive values of IGF-1 during the early postnatal period. Finally, in Chapter 5, I describe that age-related improvement and senescence in reproductive performance varies with social dominance rank among female hyenas. Cumulatively, my dissertation is an exploration of how physiological mechanisms may be used to understand social, physiological, and evolutionary forces operating in a free-living social carnivore. My work offers a unique contribution to the field of life-history evolution and furthers our understanding of the mechanisms that give rise to it.
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