A Low Phytoestrogen Diet Reduces the Proceptivity But Not the Attractivity of Meadow Voles (Microtus pennsylvanicus)

The literature is replete with studies showing that phytoestrogens can impact the reproductive physiology of a wide variety of vertebrates. However, the results of many of these studies provide mixed results, with phytoestrogens exerting an estrogenic effect, antiestrogenic effect, or no effect on reproductive physiology across taxa and within species. Less is known about the role phytoestrogens may play in the sexual behavior of vertebrates and most of those studies have focused on rats and mice, and again produced mixed findings on the impact of phytoestrogens on the sexual behavior of rodents. In this study, we determined whether the removal of dietary phytoestrogens impacted two of the three components of sexual behavior: attractivity and proceptivity in meadow voles, Microtus pennsylvanicus. Attractivity refers to the attractiveness of the scent marks male and female meadow voles produce to opposite-sex conspecifics, whereas proceptivity refers to the interest voles have in investigating opposite-sex conspecifics or their scent marks. We tested the hypothesis that the amount of phytoestrogens in the diet will induce different effects on the attractivity and proceptivity of voles by maintaining voles on either a moderate phytoestrogen diet (standard rodent chow) or a low phytoestrogen diet. The results showed that the attractiveness of the scent marks of voles was not affected by whether they were fed either a moderate or low phytoestrogen content diet. However, voles fed a low phytoestrogen diet did not behave proceptively toward opposite-sex conspecifics, spending similar amounts of time investigating the scent mark of the opposite-sex donor and that of the same-sex donor. Thus, voles that eat a low phytoestrogen diet may be less likely to find a mate and may have lower mating and reproductive success relative to that of voles that eat a diet containing moderate phytoestrogens. Our findings also lend support to the conclusions reached by some studies of nonhuman primates, rodents, ungulates, fish, and birds in which exposure to phytoestrogens produced estrogenic effects for certain sexual behaviors and no effect on other sexual behaviors.