Free female choice in house mice: Leaving best for last
Rolland C., Macdonald DW., De Fraipont M., Berdoy M.
We investigated female multiple mating in the house mouse (Mus musculus), a promiscuous mammal that exhibits male-male competition. Our experimental design, which allowed females free movement between confined dominant and subordinate males, enabled the study of females' preferences and their mating strategies unconstrained by direct male-male competition. We found that: (1) Females were actively promiscuous, always switching male after the first mating session. (2) They accepted more intromissions and ejaculations from the dominant than from the subordinate male. Female preference for dominant males was active rather than the 'passive' result of an enhanced willingness or ability by the dominant males to copulate. (3) The preference exhibited during mating was not apparent outside the period of receptivity: females neither spent more time with odours of dominant males nor with these individuals themselves, outside oestrus. Females began to spend more time with dominant males only two hours before the start of mating. (4) Females were indiscriminate in their choice of male during the first mating session. Instead, they mated with the preferred male last. (5) Finally, there was evidence that the males' mating patterns were, in turn, influenced by the females' preference (exhibited a few hours before mating). Subordinate males, which had less access to females, tended to ejaculate as soon as possible, whereas the mating pattern of dominant males was more consistent with mate guarding.