Does the winner–loser effect determine male mating success?

Abstract

Winning or losing a fight can have lasting effects on competitors. Controlling for inherent fighting ability and other factors, a history of winning often makes individuals more likely to win future contests, while the opposite is true for losers (the 'winner-loser effect'). But does the winner-loser effect also influence a male's mating success? We experimentally staged contests between male mosquitofish () such that focal males either won or lost three successive encounters with stimulus males. We then placed a size-matched (to control for inherent fighting ability) winner and loser with a female and monitored their behaviour ( = 63 trios). Winners spent significantly more time associating with the female. Winners did not make more copulation attempts, nor have a greater number of successful attempts. There was, however, a significant effect of male size on the number of successful copulation attempts: success decreased with male size for losers, but size had no effect on the success rate of winners.

Winners have higher pre-copulatory mating success but losers have better post-copulatory outcomes

“…Here, we used randomly assigned winners and losers and found that the outcome of a variety of reproductive competitions can be significantly affected by the previous fighting experience. Previous studies have documented that the experience of winning or losing can influence the expression of pre- [7] and post-copulatory reproductive traits [12]. We add to these findings by documenting the differential effects of winning and losing on pre-and post-copulatory success.…”

“…with females, or losers actively avoiding winners to reduce the potential costs of further fighting. The winners, however, did not make more copulation attempts or mate more often than the losers [7]. In other species, similar protocols have demonstrated that female choice may also influence the mating success of winners and losers.…”

The effect of brief or prolonged bouts of winning or losing male-male contests on plasticity in sexually selected traits

“…We then measured a set of traits that are under pre-or post-copulatory sexual selection. We randomly selected focal males from the stock population to test for winnerloser effects in males of all sizes to extend the findings of Harrison et al (2018). We assigned the very smallest (< 18 mm) and largest (> 25 mm) males as rival competitors.…”

“…Males were then kept in individual 1 L tanks for one week prior to competitive trials. Focal males were randomly assigned to have either a winning or losing experience by being paired with either a smaller or larger competitor, respectively (see Harrison et al 2018). Size differences are an important determinant of social dominance in mosquitofish (Caldwell and Caldwell 1962).…”

“…We expected male and female body size to affect pre-copulatory mating behaviour (e.g. Harrison et al 2018). We again fit GLMMs (negative binomial error) for each of the four precopulatory traits.…”