APA Dictionary of Psychology

competition between the sperm of different males to fertilize the eggs of females that mate with multiple males. Among nonhuman animals, males have several strategies for dealing with sperm competition, including mate guarding, leaving an ejaculatory plug in the female genitalia to prevent other males from mating, or removing sperm from previous males prior to mating. Females have tactics to counter these strategies (see cryptic female choice). In the muriqui monkey of Brazil, for example, males produce sperm plugs that block the vagina but both females and other males can remove these plugs.