The effects of food restriction and testosterone level on reproductive success in wild house mice, Mus musculus

Testosterone levels in males can be elevated by situations such as aggressive encounters with conspecifics or the proximity of reproductive females, and lowered by stressors such as food restriction. Numerous studies of small mammal species have shown that females prefer the odor of males with high testosterone levels compared with males with low testosterone levels. No studies, however, have shown directly whether female odor preferences result in increased male reproductive success. My research examined the effects of food restriction and differing levels of testosterone of males on female odor and nesting preferences and male reproductive success in wild house mice, Mus musculus. Specifically, females were tested with males that had been food restricted during gestation or postweaning, or males that had been phenotypically engineered to have high or low testosterone levels.; In food-restriction and testosterone-level experiments, differential relationships resulted between female investigation time of male odors and male reproductive success. In the food-restriction experiments, an inverse relationship existed between female investigation time of male odors and the number of offspring a male then sired, while testosterone-level experiments revealed a positive relationship between female investigation time of male odors and the number of offspring sired by the male. A further contrast between experiments was seen in the relationship between the testosterone level of males and the paternity of offspring. In food-restriction experiments, the testosterone level of males had a significant, but weak relationship with paternity of offspring. There was no relationship, however, between testosterone level and paternity of offspring in testosterone-level experiments.; While the study revealed relationships between female investigation time of male odors and male reproductive success, the utilization of testosterone levels as a proximate cue for females when investigating male odors was not clear and merits further attention. In addition, this study questions the use of female odor preference tests when testing female preferences of mates.; Future studies that examine physiological mechanisms need to incorporate both natural-manipulation and phenotypic-engineering methods when testing female odor preferences of males and male reproductive success. In addition, both laboratory and field experiments are needed to accurately assess relationships between behavior and physiology in small mammal species.