Editing Animal sexual behaviour (section)

===Polygamy===

Polygamy is defined as a mating structure in which a single individual of one gender has exclusive access to several individuals of the opposite gender.  It takes two main forms - polygyny and polyandry.  As polygyny is the most common form of polygamy among vertebrates (including humans, to some extent), it has been studied far more extensively than polyandry.

====Polygyny====
In some species, notably those with [[harem]] male structures, only one of a few males in a group of females will mate. This is also known as [[polygyny]] in [[sociobiology]].<ref>Technically, [[polygyny]] in sociobiology and zoology is defined as a system in which a male has a relationships with more than one female, but the females are predominantly bonded to a single male.</ref> Should the active male be driven out, killed, or otherwise removed from the group, in a number of species the new male will ensure that breeding resources are not wasted on another male's young.<ref>This section and examples taken from:[[Robert Sapolsky]] ''Why Zebras Don't get Ulcers'', p.140-141.</ref> The new male may achieve this in many different ways, including:
* Competitive [[infanticide (zoology)|infanticide]]
:in [[lion]]s and some [[monkey]]s the new male will kill other young; therefore, the females, which are no longer [[lactation|nursing]], rapidly become [[sexual receptiveness|receptive]] again.
* [[Harassment]] to [[miscarriage]]
:amongst wild [[horse]]s and [[baboon]]s, the male will "systematically harass" pregnant females until they miscarry.
* [[Pheromone]] based spontaneous abortion
:in some [[rodent]]s such as [[mouse|mice]], a new male with a different scent will cause females who are pregnant to spontaneously fail to implant recently fertilized eggs. This does not require contact; it is mediated by [[scent]] alone. It is known as the [[Bruce effect|Bruce-Parkes effect]].