Extra-pair copulations (EPC's) and Extra-pair paternity (EPP's) best studied in birds and humans, where they are surprisingly common in species that were presumed to be monogamous or polygynous. 95% of birds presumed monogamous, but across species the mean rate of EPP is 13% (range 0-76). Extrapair copulations are not restricted to monogamous species; they also **
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Petrie, M., D. Doums, and A. P. Moller. 1998. The degree of extra-pair paternity increases with genetic variability. P. N. A. S. (USA) 16:9390-9395. Could be characterized as cryptic polyandry.