In several BMN 673 datasheet plural breeders where female competition is unusually intense, the genitalia of mature females show signs of masculinization, which in some cases, appear to mimic male traits (Licht et al., 1992, 1998; Drea et al., 1998; Glickman et al., 1998). For example, in spotted hyenas, mature females have an extended

clitoris that mimics the male’s penis and the sexes can be difficult to tell apart (Kruuk, 1972; Glickman et al., 1998). Although hyenas are the best known example, the genitalia of adult females also show evidence of masculinization in other species where females compete intensely, including some lemurs and golden moles (Ostner, Heistermann & Kappeler, 2003; Drea, 2007). Early explanations of masculinization of female genitalia suggested that it represented PLX4032 cell line a non-adaptive by-product of elevated maternal androgen levels affecting sexual differentiation during early development, or of increased sensitivity to androgens (Racey & Skinner, 1979; Frank, 1997). However, several empirical observations suggest that this is not an adequate explanation.

First, experimental suppression of androgenization during pregnancy does not prevent female genital masculinization, suggesting that genetic factors are involved (Drea et al., 1998). Second, genital masculinization can disappear when individuals reach an age where it no longer serves any purpose. For example, transient masculinization has recently been found in two solitary carnivores, the Malagasy fossa (Hawkins et al., 2002) and the striped hyena (Wagner et al., 2007) as well as in red-fronted lemurs (Barthold, Fichtel & Kappeler, 2009). In fossas, juvenile females develop an enlarged spinescent clitoris supported by an os clitoridis and a pigmented secretion on the fur MCE公司 underparts,

which, in adults, is confined to males (Hawkins et al., 2002). In addition, in the sexually dichromatic red-fronted lemurs, where competition among females is intense, female infants show transient ‘fur masculinization’ (Barthold et al., 2009). One possible explanation is that sexual mimicry may allow young females to deflect aggression from other females. For example, in spotted hyenas, the striking pseudo-penis and pseudo-scrotum of female spotted hyenas may allow females to reduce the aggression they receive from strangers when crossing the territory of another group (Muller & Wrangham, 2002), although other explanations have been suggested (East et al., 2003). Adaptive explanations of sexual mimicry are strengthened by evidence that, in some species where there is intense competition between males, adolescent males show evidence of transient feminization.

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