The spotted hyena (Crocuta crocuta) is one of the most distinctive carnivores in the African ecosystem, known for its unique vocalizations and highly organized social structure. This species challenges typical mammalian norms due to the remarkable degree of masculinization exhibited by its females. The unique characteristics of the female spotted hyena are deeply intertwined with her anatomy, dominance, and the significant challenges she faces in reproduction.
Addressing the Terminology Question
A female hyena is simply referred to as a female hyena or, informally, as a sow, unlike species with specialized terms like “lioness” or “tigress.” The spotted hyena does not possess a unique, single-word designation for its adult female. Hyenas live in large, cooperative units known as a clan or a cackle. The most dominant female in a clan is sometimes informally called the matriarch, reflecting her position at the top of the social hierarchy.
The Unique Anatomy of the Female Hyena
The primary reason for confusion regarding the female hyena’s sex stems from her unusual reproductive anatomy. The female spotted hyena lacks an external vaginal opening, possessing instead a highly elongated clitoris, commonly called a pseudo-penis or phallus, that is structurally identical to the male’s penis. The female uses this structure to urinate, copulate, and give birth.
This morphological feature is an example of virilization, where the external genitalia resemble the male’s. The female also possesses a fleshy pouch similar to a scrotum, though it contains no testes. Scientists link this masculinization to high concentrations of androgens, specifically androstenedione, produced by the placenta late in gestation.
The clitoris is traversed by a single, long urogenital canal, which serves as the pathway for all reproductive and excretory functions. This anatomical arrangement means that sexing a spotted hyena is difficult for an untrained observer, as the external differences are minimal. The unique morphology acts as a mechanical barrier, ensuring that copulation can only occur with the full cooperation of the female, giving her complete control over mating.
Social Structure and Matriarchal Dominance
The female’s physical masculinization is mirrored in the species’ social structure, a strict matriarchy where females dominate all males. Female spotted hyenas are physically larger and heavier than their male counterparts. Females typically weigh between 120 and 150 pounds, while males weigh 100 to 130 pounds.
This size difference, combined with high aggression, ensures that the lowest-ranking female holds a higher social position than the highest-ranking male. Dominance is inherited matrilineally; offspring of a high-ranking female automatically assume a high rank. This system is reinforced because females remain in their birth clan, establishing alliances, while males disperse to join new clans at the bottom of the hierarchy.
High levels of androgens experienced prenatally contribute to both the female’s physical traits and her aggressive, dominant behavior. This hormonal exposure may predispose female cubs to the assertive demeanor necessary to maintain their social standing. Females enforce the hierarchy, ensuring they and their cubs have priority access to food resources, especially at a kill site.
Reproductive Challenges and Parturition
The female’s unique anatomy presents significant challenges during the process of giving birth, known as parturition. The single, narrow urogenital canal running through the rigid pseudo-penis must stretch to allow the cub’s passage. Unlike most mammals, the female hyena lacks the elasticity of a typical vulva and vagina.
This difficult process leads to a high rate of dystocia, or difficult birth, especially for first-time mothers. First pregnancies often result in a stillbirth rate of approximately 60%. The birthing canal is so restrictive that the clitoral tissue often tears during the cub’s passage, resulting in a wound that takes several weeks to heal.
This physical difficulty highlights a significant biological cost associated with the female’s masculinized anatomy. Newborn cubs, which weigh around 3.3 pounds, are born highly precocial, with their eyes open and teeth erupted. This advanced state may be an evolutionary adaptation to help them survive the initial high-risk period.