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Jumping Spider Dances: Sex ratios and Operational Sex Ratios

The "sex ratio" in a population is the ratio of females to males. If there are equal numbers of males and females, the ratio is 1 : 1.

picture of equal numbers of male and female spiders

However, although there may be equal numbers of males and females, the "operational sex ratio" (ratio of sexually receptive males to sexually receptive females) can be quite different. If half the females are already mated, or if half the males are sexually immature and can't mate yet, the "operational sex ratio" will be quite different from the actual sex ratio.

Males have enough sperm to inseminate many females (with sperm to spare).
Females can only produce 10 eggs at a time, and one mating can easily fertilize all the eggs.

Therefore, because the potential rate of reproduction is quite different between the sexes, at any one time there are many more sexually receptive males than sexually receptive females.

same image but with half the females x-ed out

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