TABLE 4 ∣.

Putative pathways to reductions in physical sexual dimorphism and reduced “Masculine” traits.

Hypothesized pathways	Evidence in the prairie vole
1. Reduced levels of testosterone or DHT	High levels of T(Lansing et al., 2013) DHT levels have not been reported
2. Failure to convert testosterone to DHT, possibly due to variation in the 5a-reductase enzyme	??
3. Genetic or epigenetic variation in the androgen receptor (AR)	??
4. Genes on sex chromosomes vulnerable to epigenetic modification?	??
5. Presence of inhibitory factors such as stress or high levels of glucocorticoids	Very high corticosterone, likely across the life cycle (DeVries et al., 1995, 1996) Glucocorticoid receptor insensitivity (Taymans et al., 1997)
6. Exposure to oxytocin in the perinatal period	Reduced sex difference in the brain (Yee et al., in preparation) Decreased AVP V1a receptors (both sexes; Bales et al., 2007b) May act to demasculinize via anti-inflammatory pathways (Nugent et al., 2015)