Sex ratio '' Multiple types of male-male competition may occur in a population at different times depending on the conditions. Competition variation occurs based on the frequency of various mating behaviours present in the population. In some species, particularly
parasitoid wasps like those in the genus
Sclerodermus, females lay eggs communally and their offspring mate locally, creating strong local mate competition (LMC). Under classical LMC theory, the sex ratio is expected to become less biased as more females (foundress) contribute offspring, since their sons compete with a wider pool of males, not just their brothers. However, empirical studies have found persistently extreme female-biased sex ratios in
Sclerodermus, even in large multi-foundress groups. Recent models propose that dominant foundresses suppress male production by subordinates, either by
infanticide or by social dominance that prevents them from producing sons at all. The risk of competition must therefore be worth the value of the resource. A male is more likely to engage in competition for a resource that improves their reproductive success if the resource value is higher. While male-male competition can occur in the presence or absence of a female, competition occurs more frequently in the presence of a female.
Winner–loser effects A third factor that can impact the success of a male in competition is
winner-loser effects. Burrowing crickets,
Velarifictorus aspersus, compete for burrows to attract females using their large mandibles for fighting. Female burrowing crickets are more likely to choose winner of a competition in the 2 hours after the fight. The presence of a winning male suppresses mating behaviours of the losing males because the winning male tends to produce more frequent and enhanced mating calls in this period of time. == Effect on female fitness ==