Sex in the morning or the evening?

In fowl, the probability that an insemination results in fertilization is lowest around midday when oviposition occurs and highest in the evening, indicating that both males and females should maximize copulation efficiency by mating in the evening.

In research appearing in the July issue of The American Naturalist, researchers at the University of Oxford found that, as expected, male fowl are more sexually active in the evening. Female fowl on the other hand, change their daily pattern of sexual activity in response to the sex ratio of a population.

Females solicit sex in the evening in populations that are heavily female-biased, where sexual harassment by males is minimal, and females have more control of copulation. However, in male-biased populations, male sexual harassment of females is intense, especially in the evening. Here, females solicit sex early in the morning and avoid males in the evening. This behavioral plasticity in sexual behavior may enable females to reduce the cost of mating while maintaining some control over paternity.

Citation: Hanne Løvlie and Tommaso Pizzari, "Sex in the morning or in the evening" females adjust daily mating patterns to the intensity of sexual harassment" (open access) The American Naturalist (2007) 170:E1–E13, DOI: 10.1086/518180

Source: University of Chicago