Evaluating drivers of female dominance in the spotted hyena: R code and data

Introduction: Dominance relationships in which females dominate males are
rare among mammals. Mechanistic hypotheses explaining the occurrence of
female dominance suggest that females dominate males because 1) they are
intrinsically more aggressive or less submissive than males, and/or 2)
they have access to more social support than males. Methods: Here, we
examine the determinants of female dominance across ontogenetic
development in spotted hyenas (Crocuta crocuta) using 30 years of detailed
behavioral observations from the Mara Hyena Project to evaluate these two
hypotheses. Results: Among adult hyenas, we find that females
spontaneously aggress at higher rates than males, whereas males
spontaneously submit at higher rates than females. Once an aggressive
interaction has been initiated, adult females are more likely than
immigrant males to elicit submission from members of the opposite sex, and
both adult natal and immigrant males are more likely than adult females to
offer submission in response to an aggressive act. We also find that adult
male aggressors are more likely to receive social support than adult
female aggressors, and that both adult natal and immigrant males are 2-3
times more likely to receive support when attacking a female than when
attacking another male. Across all age classes, females are more likely
than males to be targets of aggressive acts that occur with support.
Further, receiving social support does slightly help immigrant males
elicit submission from adult females compared to immigrant males acting
alone, and it also helps females elicit submission from other females.
However, adult females can dominate immigrant males with or without
support far more often than immigrant males can dominate females, even
when the immigrants are supported against females. Discussion: Overall, we
find evidence for both mechanisms hypothesized to mediate female dominance
in this species: 1) male and female hyenas clearly differ in their
aggressive and submissive tendencies, and 2) realized social support plays
an important role in shaping dominance relationships within a clan.
Nevertheless, our results suggest that social support alone cannot explain
sex-biased dominance in spotted hyenas. Although realized social support
can certainly influence fight outcomes among females, adult females can
easily dominate immigrant males without any support at all.