Up to day 15 after male emergence, there were 206 encounters with one day old females and 202 encounters with three days old females, among them, only 80 (38.8%) and 126 (62.3%) of the females, respectively, copulated as evidenced by the presence of fertile eggs.
However, a negative correlation was observed between the male age and the number of females that copulated (one day old females: r = -0.621; df=23; P=0.0009) (three days old females: r = -0.786; df=27; P<0.0001).
In the male-male competition experiment, when two differently sized males and one female were combined in one tank on days three and four, the larger male copulated with the female five times, but the smaller male never copulated with the female (Fisher's exact test, 0.05 < P < 0.1).
Our results show that, although the number of offspring per egg sac decreased, females that only copulated once could produce up to six viable clutches.
(1996) challenged this interpretation and showed by another empirical study of Scatophaga that Ward's results could be equally or better explained by differential sperm displacement rates: when larger males copulated second they displaced previously stored sperm more rapidly than smaller males.
(1992) in another reptile, the adder Viperus berus: females copulated indiscriminately with several males, and the more partners a female had, the lower the level of mortality and morphological abnormalities in her offspring.
In the second experiment, in which males carrying two mites competed against uninfested males, significantly fewer infested males (31%) copulated
compared to uninfested males (68%) (table 4).
The drunken bout didn't affect the male rodents' interest in sex: The hungover males copulated
with the same vigor as 75 control males that were also paired with female rats.
Four of the seven "secondary males" copulated
with females, fertilizing up to 70 percent of the eggs and generating normal offspring, the investigators say.