Mating System - in Animals

In Animals

See also: Polygyny threshold model, Monogamous pairing in animals, and Animal sexual behavior

The following are some of the mating systems generally recognized in animals:

• Monogamy: One male and one female have an exclusive mating relationship. The term "pair bonding" often implies this.
• Polygamy: Three types are recognized:
  • Polygyny (the most common polygamous mating system in vertebrates so far studied): One male has an exclusive relationship with two or more females
  • Polyandry: One female has an exclusive relationship with two or more males
  • Polygynandry:Polygynandry is a slight variation of this, where two or more males have an exclusive relationship with two or more females; the numbers of males and females need not be equal, and in vertebrate species studied so far, the number of males is usually less.
• Promiscuity: A member of one sex within the social group mates with any member of the opposite sex.

These mating relationships may or may not be associated with social relationships, in which the sexual partners stay together to become parenting partners. As the alternative term "pair bonding" implies, this is usual in monogamy. In many polyandrous systems, the males and the female stay together to rear the young. In polygynous systems where the number of females paired with each male is low, the male will often stay with one female to help rear the young, while the other females rear their young on their own. In polygynandry, each of the males may assist one female; if all adults help rear all the young, the system is more usually called "communal breeding". In highly polygynous systems, and in promiscuous systems, paternal care of young is rare, or there may be no parental care at all.

It is important to realize that these descriptions are idealized, and that the social partnerships are often easier to observe than the mating relationships. In particular:

• the relationships are rarely exclusive for all individuals in a species. DNA fingerprinting studies have shown that even in pair-bonding, matings outside the pair (extra-pair copulations) occur with fair frequency, and a significant minority of offspring result from them.
• some species show different mating systems in different circumstances, for example in different parts of their geographical range, or under different conditions of food availability
• mixtures of the simple systems described above may occur.