Fig. 2

Mean hormone concentration (ng/mL) ± standard error of the mean. An interaction between sex and group indicates that males, but not females, had increased circulating testosterone following 1 week of pairing. Females had increased estradiol and progesterone at 1 month, although estradiol declined after becoming a breeder. Estradiol, but not progesterone, was increased in males that produced a litter. *p < .05; &p < .10. ns non-significant