Adult Sex Ratio in Social Systems: Causes and Consequences in Primates

Saccà, Tommaso (2020) Adult Sex Ratio in Social Systems: Causes and Consequences in Primates. Master's Thesis / Essay, Ecology and Evolution.

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Abstract

Adult sex ratio is a central topic in sociobiology and has been hypothesized to be linked to social behavior and population dynamics. This essay aim is to survey the literature on the general theory concerning which factors cause skewed adult sex ratio and how this influences social systems, specifically in primates. Shifts in adult sex ratio are bound to specific proximate causations, namely changes in birth sex ratio and sex-biased mortality. In primates, while biases in birth sex ratio are present, the main drivers of biases in adult sex ratio are sex-specific behaviors (i.e. male-biased risky behaviors) and physiological differences (male-biased sexual dimorphism), and the resulting male-biased mortality results in the typical female-biased adult sex ratio observed in most species. Consequences of different adult sex ratio on social systems mainly revolve around mating systems, specifically in the relationship between decreasing mating skew and increasing female proportion in groups. Also, an increased male proportion in primate groups influence dominance hierarchies, increasing female dominance over males. Among primates, lemurs show an unusual, even adult sex ratio, and their case is explored in the discussion to identify the possible causes of it and the consequences on their social systems.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Hemelrijk, C.K.
Degree programme:	Ecology and Evolution
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	18 May 2020 07:52
Last Modified:	18 May 2020 07:52
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/21885

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