Rare male aggression directed toward females in a female‐dominated society: Baiting behavior in the spotted hyena

Abstract

Spotted hyenas (Crocuta crocuta) are gregarious carnivores. The females are socially dominant to males, and adult males rarely direct aggression toward adult females. This study analyzed all cases in which adult immigrant males behaved aggressively toward adult females in a large population of freeliving hyenas in Kenya, observed for 11 years. Our goals were to describe the conditions under which male attacks on females occur, and address possible adaptive functions. Most aggression directed by adult immigrant males against females occurred when coalitions of two or more males attacked a single adult female, who typically responded by defending herself and fighting back. Male aggression against females frequently occurred at sites of ungulate kills, but males never behaved aggressively toward females over food, and all male attacks on females were unprovoked. Although no mounting or other copulatory behaviors ever occurred during or immediately after an attack, the number of male attacks on females peaked around the time of conception. Daily rates at which males attacked females did not vary with female social rank. However, daily attack rates did vary significantly with female reproductive state, and the highest rates of male attack on females were observed during the two stages of the reproductive cycle during which females were most likely to conceive litters. The adaptive significance of male aggression against females in this species remains unknown, but a tight association between male attacks on females and a female's time of conception provides strong evidence of some role for male aggression in hyena sexual behavior. In particular, our data are consistent with hypotheses suggesting that male aggression toward females in this species either serves to inform females about male fitness or represents sexual harassment.

Sex and the Frontal Cortex: A Developmental CT Study in the Spotted Hyena

“…Captive female spotted hyenas are more likely than males to initiate acts of aggression [Glickman et al, 1993;, and in the wild females emit aggressive acts at higher rates and intensities than do males [Szykman et al, 2003]. We have anecdotally observed in the field that wild male spotted hyenas, as they start to exhibit effects of anesthesia during immobilizations, sometimes direct aggression inappropriately at females and their cubs, but they never do this under any other circumstances.…”

Society, demography and genetic structure in the spotted hyena

“…That is, adult females are larger and more aggressive than adult males, they are socially dominant to all adult males born elsewhere, and the female’s genitalia are heavily ‘masculinized’ (Kruuk 1972; Frank 1986; Hamilton et al. 1986; Mills 1990; Szykman et al. 2003; Van Meter 2009).…”

“…). That is, adult females are larger and more aggressive than adult males, they are socially dominant to all adult males born elsewhere, and the female's genitalia are heavily 'masculinized' (Kruuk 1972;Frank 1986;Hamilton et al 1986;Mills 1990;Szykman et al 2003;Van Meter 2009). These unusual traits not only give females top priority of access to food, but they also give females virtually complete control over mating (East et al 1993).…”

Post-weaning maternal effects and the evolution of female dominance in the spotted hyena

“…Along with those of several lemurs and two mole rat species (Sherman et al 1991;Kappeler 1993), the societies of spotted hyenas (Crocuta crocuta) represent rare exceptions to the typical mammalian pattern of male dominance. Adult female spotted hyenas are more aggressive than males (Szykman et al 2003) and socially dominant to them in virtually all social contexts (Kruuk 1972;Tilson & Hamilton 1984;Frank 1986). Despite great interest in this unusual pattern of 'sex-role-reversed' behaviour, there is not yet a satisfactory functional explanation for the evolution of female dominance in any mammalian species.…”