Consequences of Male Chemosignals and Condition on Female Mate Choice and Reproductive Success

 Funded By:  National Science Foundation EPSCoR and
The Committee on Institutional Studies and Research

In many vertebrate species, females can distinguish among potential male mates through chemosignals emitted by males.  These chenosignals are known to communicate information such as body size, reproductive experience, kinship, dominance status, diet, and many other characteristics.  Chemosignals may, therefor, select males with odors (ie.e, chemosignals) that indicate high genetic quality.  Dr. Jill Kruper, undergraduate research students, and I investigated the effects of male chemosignals on female odor preferences and female reproductive success in the prairie vole (Microtus ochrogaster) and the house mouse (Mus musculus).  We hypothesized that 1) females prefer the odors of males of high quality and 2) females that mate with males with preferred odors will have greater reproductive success than females that mate with males with non-preferred odors.  

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In prairie voles we found a positive relationship between male testosterone level and the attractiveness of male odors to females. The relationship between testosterone level and odor attractiveness was affected negatively, however, by depriving males of food post-weaning; suggesting an influence of non-gonadal hormones. One very interesting result was that, in contrast to food-deprivation post-weaning, food-deprivation during gestation enhanced the attractiveness of male odors to females and enhanced testosterone level. Jill Kruper, a Ph.D. student, is currently determining whether male house mice (Mus musculus) with more attractive odors are preferred by females as social partners and as mates and, through paternity analyses, whether males with more attractive odors have higher reproductive success.   The dependent variables that she is investigating are the testosterone level, corticosteroid level, and the nutritional history of males.

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In house mice, our first set of experiments showed that females that were mated with males with preferred odors conceived more offspring than females that were mated with males with non-preferred odors.  There were no differences, however, in litter size at birth or growth rates of offspring.  

House mice embryos.

The number of placental scars was significantly greater in females that were paired with males with preferred odors compared with those paired with males with non-preferred odors.
The mass of the testes was significantly greater in sons born to females paired with males with preferred odors.  There was no significant difference in blood concentrations of testosterone, however.
The digestive organs of sons born to females paired with males with preferred odors were significantly heavier than those of sons born to females paired with males with non-preferred odors.
CONCLUSIONS: Females who mate with males with preferred odors may produce more offspring than if mated with males with non-preferred odors. The sons born to females who mated with preferred males may have greater fitness due to their larger testes and digestive tract. Females may increase their fitness by mating with males with preferred odors.