Engagement in extra-pair copulations is common in some species; other species have breeding systems that are polygynous (many females) or, rarely, polyandrous (many males).
For females, possible benefits of extra-pair copulation include getting better genes for her offspring and insuring against the possibility of infertility in her mate.
One such tactic attributed to older, subordinate males involves forming alliances to combat higher-ranking males in order to achieve access to females for copulation.
