9.3 An Introduction to Operational Sex Ratios

Operational sex ratio (OSR) is the ratio of sexually receptive males to sexually receptive females, (typically expressed as male:female ratio). The term “operational” refers to the idea that it is the sex ratio of sexually active, or sexually competing, individuals, that matters to much of our discussion. For example, a population’s OSR can affect the intensity of competition between same-sex individuals for access to mates.

Figure 9.3 Various sex ratios

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