Mating Systems

Ecological and evolutionary considerations, such as the availability of food resources and unequal investment by the sexes in offspring, underlie differences in the mating systems employed by most species. Mating systems include promiscuity, polygamy (either polygyny or polyandry), and monogamy. These systems can manifest themselves in a simultaneous or serial manner, and can be expressed annually or seasonally. Farm animals are typically promiscuous or polygynous. Promiscuous animals have no exclusive breeding rights over any other individual. Typically, much copulation occurs during periods of female receptivity, yet no pair bonds or extended associations are formed. This is the mating system most commonly observed among cattle, sheep, goats, swine, and chickens. Some promiscuous species can also show simultaneous polygyny, in which the mating system may involve a male forming a bond with many females for variable periods. Simultaneous polygyny is typical of species in which the male forms harems, such as in horses. Mating systems in intensive confinement may differ from those in a more natural environment due to housing and management. Domestic fowl, for example, are really a polygynous species, but in intensive production systems the male is unable to maintain a harem, and the mating system becomes promiscuous instead. The promiscuous and polygynous mating systems of most livestock species served as a preadaptation that contributed to the success of domestication, because monogamy or other pair bond formation would likely have hindered animal breeding programs.

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