ANIMAL BEHAVIOUR, 2000, 59, 371–378 doi: 10.1006/anbe.1999.1316, available online at http://www.idealibrary.com on Free female mate choice in house mice affects reproductive success and offspring viability and performance LEE C. DRICKAMER*, PATRICIA ADAIR GOWATY† & CHRISTOPHER M. HOLMES* *Department of Zoology, Southern Illinois University †Institute of Ecology, University of Georgia (Received 24 May 1999; initial acceptance 15 July 1999; final acceptance 21 September 1999; MS. number: A8356R) We tested a critical assumption of sexual dialectics theory (Gowaty 1997, Feminism and Evolutionary Biology, Chapman & Hall) using house mice, Mus musculus. We asked if female house mice accrue viability benefits for their offspring when they mate with males they prefer versus with males they do not prefer. Our experiment was designed to eliminate or control other mechanisms of reproductive competition besides female mate choice. After allowing females to discriminate behaviourally between two males, which were at random with respect to phenotypic variation discriminating females were paired with preferred (P) or nonpreferred (NP) males. We then tested whether females mating with males they preferred had offspring of higher viability than females mating with nonpreferred males. In pairwise comparisons, we tested for differences in offspring performance in dominance contests and in nest- building skill. At weaning, we exposed half of the pups to cold stress. We tested progeny performance and viability in the laboratory or in outdoor field enclosures. In comparison to P females, NP females produced significantly fewer litters. Sons from P matings were socially dominant to sons from NP matings. Adult offspring from P matings built better nests than those from NP matings. In field enclosures significantly fewer NP than P offspring survived to 60 days after introduction. Male and female progeny from P matings established larger home ranges and constructed better nests than progeny from NP matings. This is the first demonstration of progeny viability differences for females allowed to express mate preferences between males presented to them at random.  2000 The Association for the Study of Animal Behaviour Darwin (1871) posited female choice of mates as a mech- anism of reproductive competition among males. Based on Bateman’s (1948) experiment, Williams (1966) and Trivers (1972) revived the idea of female choice as a potent sexually selected mechanism accounting for the evolution of the traits of males, and it is now accepted that female choice can lead to differential mating by males and the evolution of male traits (Andersson 1994). Most modern investigations of mate preference show how female discrimination among potential males results in variation in traits in sons. However, there also may be other important effects on the fitness of choosers. Reynolds & Gross (1992), Niccoletto (1995) and Wilkinson (1998), for example, showed that sexually selected traits in sons also correlate with other fitness measures, showing that sexually selected characters may act as indicators of male genetic quality. Unlike most other studies of female mate preferences (Andersson 1994; Wagner 1998), our experiment tested whether female preference for mates yields fitness benefits for females independent of investigator-measured or manipulated phenotypic traits in to-be-discriminated males. We specifically tested whether females mated to males they preferred would have higher viability off- spring than females mated to males they did not prefer. Here we report results on house mice, Mus musculus. Our interest in offspring viability was motivated by a critical assumption of a sexual conflict theory (Gowaty 1997) called sexual dialectics that posits that the dynami- cal character of affiliative and antagonistic behaviour of the sexes is fuelled by selection against evolving rather than existing strains of pathogens and parasites. If mate choice is caused by the threat of evolving pathogens, the best mate for any one female may not be the best mate for another, because females should prefer to mate with males with complementary alleles at crucial immune- coding loci. Thus, because females themselves will pro- vide half of the solution to the equation of immunity alleles in their offspring, and assuming that females are unique, the most complementary male is unlikely to be the most complementary for most females. If freely Correspondence and present address: L. C. Drickamer, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, U.S.A. (email: lee.drickamer@nau.edu). 0003–3472/00/020371+08 $35.00/0  2000 The Association for the Study of Animal Behaviour 371