The unique biology of the spotted hyena (Crocuta crocuta) defies typical mammalian norms. In this species, females are the social leaders and the physically dominant sex. Female spotted hyenas are generally larger, heavier, and more assertive than their male counterparts, reversing the sexual size dimorphism seen in most other carnivore species. This rare female supremacy results from a complex interplay between physical size, unique hormonal environments, and a rigid, female-led social structure.
Comparing Physical Attributes
Female spotted hyenas consistently outweigh the males, providing the most direct measure of their strength. Adult females typically weigh between 44.5 and 63.9 kilograms, while males range from 40.5 to 55.0 kilograms. This difference means a female may be 6.6 kilograms heavier than a male, giving her a significant advantage in physical confrontations.
Females are also structurally more robust, showing greater girth and approximately 10% more brawniness in overall body size, particularly in the head and neck. This increased mass and muscularity translate directly into greater physical power, displayed in competitive feeding and territorial defense. While both sexes possess one of the strongest bites in the animal kingdom (1,100 PSI), the female’s size secures her dominance in disputes over food. Due to their greater size, females are better equipped to crush bone and maintain access to a carcass against competitors, including males.
The Biological Basis for Female Masculinization
The female spotted hyena’s unusual physical and behavioral traits are rooted in a distinctive prenatal hormonal environment. During gestation, the placenta produces large amounts of androgens. This high level of exposure to masculinizing hormones affects the developing brain and body of both male and female cubs. Consequently, both sexes are born with a heightened predisposition toward aggression and dominance behavior, traits instrumental for survival in their highly competitive society.
This hormonal influence is also responsible for the female’s unique external anatomy, known as the pseudo-penis, or peniform clitoris. This elongated organ, traversed by a urogenital canal, is used for urination, copulation, and giving birth. The female lacks an external vaginal opening, as her labia are fused to form a structure resembling a male’s scrotum.
The highly masculinized genitalia come with a significant biological cost. The narrow, inflexible birth canal can lead to complications during the female’s first delivery. The difficulty of passing a cub through the pseudo-penis results in a high mortality rate for first-born cubs, with estimates suggesting that 65 to 70 percent do not survive. This evolutionary trade-off suggests that the benefits of producing aggressive, high-ranking offspring outweigh the risks of a dangerous birth.
Matrilineal Social Structure and Dominance
The physical and hormonal advantages of the female sex directly underpin the spotted hyena’s strict, female-led social organization, known as a matrilineal hierarchy. Within a clan, females hold the highest social ranks, and this dominance is so rigid that the lowest-ranking female is still dominant over the highest-ranking male. This social structure dictates that females have preferential access to resources, securing the best feeding spots on a kill and receiving deference from all males.
Social rank is largely inherited from the mother, not earned by the cub through fighting alone. Offspring acquire a social position immediately below that of their mother. This rank is maintained through the mother’s active intervention and support during aggressive interactions with other clan members. High-ranking mothers are more successful in defending their cubs, allowing the young to learn who they can dominate from a very early age.
Males born into the clan eventually disperse and join a new group, where they assume the lowest available rank upon immigration, reinforcing their subordinate status. For a male to successfully mate, he must gain the female’s full cooperation, necessary due to the female’s pseudo-penis anatomy. The female’s physical size, hormonal-driven aggression, and control over copulation ultimately cement her as the stronger and more dominant force in the spotted hyena’s complex social world.