Meeting Abstract
Traditionally in mammals, males are the more aggressive sex, owing in part to the action of androgens; however, in some species, the roles are reversed. In the most iconic example of aggressively mediated female dominance – the spotted hyena (Crocuta crocuta) – females are morphologically and behaviorally masculinized. Although testosterone (T) in female hyenas remains lower than in males, during gestation, ovarian androstenedione (A4) is increasingly converted to T, which has been implicated as a mediating mechanism for this sex-role reversal. The generalizability of this model to other ‘masculinized’ species remains unclear. In the meerkat (Suricata suricatta), a cooperative breeder with extreme female reproductive skew, the proximate mechanisms of female dominance are unknown. Here, we first tested for sex and status effects on adult serum concentrations of A4, T and estradiol (E2). As in hyenas, nonpregnant female meerkats (n= 30) had greater A4 concentrations than did males (n=50). More unusually, nonpregnant female T concentrations were equivalent to those of males. E2 values showed the more traditional sex difference. Moreover, within females (but not within males), dominant meerkats had greater concentrations of sex steroids than did subordinates. We next examined the effects of pregnancy on female endocrine profiles and found that gestation magnified these sex and status effects, notably raising total androgen concentrations of females well above those of males. We suggest that female meerkats are hormonally masculinized: Androgens may thus mediate female, but not male, dominance, partially explaining the extreme reproductive skew in females of this species. Supported by NSF IOS-1021633.
