Free mutual mate preferences in house mice affect reproductive success and offspring performance

When social constraints on the expression of mate preferences are absent, variation in offspring viability is predicted to favour females and males that display mate preferences. Earlier studies showed that female and male house mice, Mus domesticus, tested individually and mated with preferred (P) partners had higher reproductive success and better progeny performance than individuals mated with nonpreferred (NP) partners. Here we tested the effects of mutual mate preferences on reproductive success, offspring viability and performance. We conducted mate preference tests and created four types of reproductive pairings. One involved females and males that preferred each other (P–P); the second type had females that preferred the male but the male did not prefer the female (P–NP); the third had females that did not prefer the male but the male did prefer the female (NP–P). The last set consisted of females and males that did not prefer each other (NP–NP). We measured components of fitness for breeders (reproductive success) and offspring viability (birth-to-weaning viability and weight variation) as well as measures of offspring performance. There were no statistical differences in reproductive success of breeders or offspring viability and quality (weight variation) among the four types of pairings. There were, however, consistent differences between P–P versus NP–NP matings. The number of pups weaned, time to first litter, birth-to-weaning viability, pup body weight at birth and weaning, and the growth rates for pups of both sexes were consistently greater for progeny from P–P matings than NP–NP matings. Significant differences occurred among the four mating types in dominance of sons during aggression trials, nest construction and predator avoidance. Progeny from P–P matings displayed behaviour associated with higher fitness more often than progeny from NP–NP matings. These data show that breeders produce more highly competent progeny, most likely to survive, when social constraints on the expression of mate preferences in both sexes are relaxed.