Mate Switching and Copulation Behaviour in the Adélie Penguin

Abstract

[In monogamous species of birds sperm competition may result from either extra-pair copulations or mate switching. Copulation behaviour in individuals involved in extra-pair activity is well documented while little attention has been paid to mate switching. The aim of this study was to examine copulation behaviour in the Adelie penguin (Pygoscelis adeliae), a species in which females copulate sequentially with more than one male. 14.9% of females switched mates during the pre-laying period; all of these females engaged in successful copulations with both initial and final males. An estimated 9.8% of females engaged in successful EPCs over the same time period. Females that switched mates had on average 8 successful copulations with their initial partner while females that engaged in extra-pair copulation attempts had on average only 0.5 successful copulations with their extra-pair partner. These same females had on average 17 pair copulations per clutch. So in both cases females had significantly more copulations with their final, pair male than their initial partner or extra-pair partner. Frequencies of copulation that are higher than necessary for fertilisation are consistent with mechanisms of both last male sperm precedence and proportional representation. However there is no support for last male sperm precedence from either diurnal or seasonal patterns of copulation relative to fertilisation. It appears that a high frequency of copulation may have evolved in pair males to protect paternity against initial males in this species., In monogamous species of birds sperm competition may result from either extra-pair copulations or mate switching. Copulation behaviour in individuals involved in extra-pair activity is well documented while little attention has been paid to mate switching. The aim of this study was to examine copulation behaviour in the Adelie penguin (Pygoscelis adeliae), a species in which females copulate sequentially with more than one male. 14.9% of females switched mates during the pre-laying period; all of these females engaged in successful copulations with both initial and final males. An estimated 9.8% of females engaged in successful EPCs over the same time period. Females that switched mates had on average 8 successful copulations with their initial partner while females that engaged in extra-pair copulation attempts had on average only 0.5 successful copulations with their extra-pair partner. These same females had on average 17 pair copulations per clutch. So in both cases females had significantly more copulations with their final, pair male than their initial partner or extra-pair partner. Frequencies of copulation that are higher than necessary for fertilisation are consistent with mechanisms of both last male sperm precedence and proportional representation. However there is no support for last male sperm precedence from either diurnal or seasonal patterns of copulation relative to fertilisation. It appears that a high frequency of copulation may have evolved in pair males to protect paternity against initial males in this species.]