Sex Differences in Spotted Hyenas

The eco-evolutionary landscape of power relationships between males and females

“…Third, male-biased power has often been implicitly considered as the default state, whereas female-biased power has traditionally been viewed as anecdotal and emerging from lineagespecific oddities [16,20], such as the 'lemur syndrome' or the peculiar anatomy of female genitalia in spotted hyenas, moving the topic outside mainstream socio-ecology. These oversimplifications, and the lack of a standardised methodology to quantify intersexual power, have prevented the conceptual integration of intersexual power into the broader evolutionary theories of sexual conflict and mating systems as well as comparative analyses that could reveal general mechanisms driving biases in intersexual power.…”

“…Early empirical and theoretical studies of intersexual power have largely focused on the evolutionary drivers of female-biased power [12]. In the centre of attention were a handful of species where females were considered 'masculinised' because they possess behavioural, physiological or morpho-anatomical traits that are more strongly expressed among males in most mammals, such as large body size, aggressiveness, levels of androgens, or erectile external genitalia -as in many lemurs [13][14][15], spotted hyenas (Crocuta crocuta) [16], rock hyraxes (Procavia capensis) [17], and meerkats (Suricata suricatta) [18]. A predominant set of hypotheses has therefore emphasised the role of intrinsic attributes on female coercive potential [12,15,19].…”

“…They posited that females outcompete males when they match or surpass males in size, weaponry or fighting ability. Extensions of these hypotheses later integrated the role of behavioural and hormonal masculinisation in female empowerment [13,14,16,20]. A second set of hypotheses emphasised asymmetries in motivation that may arise from differences in life history between males and females.…”

“…Intersexual power follows a diagonal from species where power is strongly male-biased in both contexts (see Hamadryas baboons, Papio hamadryas) to strongly female-biased in both contexts (see ring-tailed lemurs, Lemur catta); mammalian societies where reproductive control is strongly female-biased and social control is strongly male-biased, or vice versa, are unlikely to emerge. Reference list: Hamadryas baboon [29,46]; chimpanzee (Pan troglodytes) and bonobo (Pan paniscus, see Box 3); Guinea baboon (Papio papio) [77] ; meerkat (Suricata suricatta) [30,78], moustached tamarin (Saguinus mystax) [79][80][81][82][83]; rock hyrax (Procavia capensis) [17,84]; spotted hyena (Crocuta crocuta) [16,28,85]; ring-tailed lemur [15,49]; cross-specific data [27,36,86].…”

“…In this species, females have complete reproductive control owing to the peculiar anatomy of their external genitalia. Females lack a vaginal opening (because their labia are fused) and instead possess an elongated and erectile clitoris through which they copulate, urinate and give birth [16]. A direct consequence is that copulation requires the full cooperation of the female and that females can actively choose when and with whom they mate [85].…”