An examination of the breeding biology of the Humboldt penguin (Spheniscus humboldti) using molecular genetic techniques

This study demonstrated that Humboldt penguins at Punta San Juan, Peru, despite forming pair-bonds, are not strictly monogamous in their mating behavior as 19.2% of the study males and 30.7% of the study females (21 nests) engaged in extra-pair copulations. Using DNA fingerprinting I demonstrated that none of these extra-pair copulations resulted in extra-pair fertilizations, as all 49 offspring were attributed to the putative father. Location of copulations support the idea that females solicit these extra-pair copulations since 89.2% of Humboldt penguin within-pair copulations occur at the home burrow, yet extra-pair copulations differ in location based on the sex of the penguin. Extra-pair copulations by males occur at their nest, whereas females conduct 92% of their extra-pair copulations away from the nest. These results are more supportive of "mate-appraisal", "ensurance-against-male-infertility", and "extra-pair-copulations-as-a-non-selected trait" hypotheses, than of "increasing-genetic diversity-of-the-brood", "good-genes", and "induction-of-sperm-competition" hypotheses.