Estrous female goats use testosterone-dependent cues to assess mates

In a promiscuous species like the domestic goat (Capra hircus), in which maternal investment is greater than paternal investment, a female may mate selectively with a more-fit male to improve her reproductive fitness. Testosterone (T) controls a large suite of male-typical behaviors and morphological characteristics. High T concentrations may be energetically costly or even detrimental to survival; thus, preventing lower quality males from falsely advertising their fitness. Three preference studies were conducted to examine if females use T-dependent cues to assess potential mates. For Experiment 1, females were given a choice between a pair of morphologically similar males, bucks (intact males) and stags (post-pubertally castrated males), during the breeding and non-breeding seasons. In both seasons, females preferred the bucks compared to stags. In Experiment 2, females were given a choice between bucks, stags and wethers (pre-pubertally castrated males) during the non-breeding season. For some comparisons, castrated males received 25 mg testosterone propionate (TP) or were untreated. Females preferred TP-treated males compared to untreated males and showed no preference when given a choice between either two TP-treated or two untreated males. In Experiment 3, females were given a choice between a pair of bucks and a pair of stags treated with 25 mg TP during monthly tests in the breeding season. At each monthly test, females preferred the males with higher T concentrations near the time of the behavior test. These studies suggest that females use T-dependent cues to assess potential mates, and T concentrations may indicate a male's overall fitness.