Spotted hyenas are carnivores known for their complex social structures and unique adaptations. A particularly intriguing aspect of their biology involves the reproductive process of female hyenas. Their method of reproduction is notably distinct and presents considerable challenges.
Unique Female Anatomy
Female spotted hyenas possess genitalia unique among mammals. They lack an external vaginal opening. Instead, their clitoris is significantly enlarged, forming a “pseudo-penis” capable of erection. The labia are fused, creating a “pseudo-scrotum.”
This pseudo-penis is a functional organ through which the female urinates, copulates, and gives birth. The development of this masculinized external genitalia is influenced by high levels of androgens, to which female fetuses are exposed. These elevated hormone levels are thought to contribute to the aggressive nature and social dominance observed in female hyenas.
The Birthing Process
The birthing process for female spotted hyenas is difficult due to their anatomy. Cubs must pass through the narrow urogenital canal within the pseudo-penis, which can be as small as 1 to 1.5 inches (2.5 to 3.8 cm) in diameter. This is challenging because hyena cubs are among the largest neonates relative to their mother’s body weight among terrestrial carnivores.
During a female’s first birth, tearing of the clitoral tissue is inevitable, causing pain and blood loss. This can lead to severe injuries and a high risk of infection for the mother. Mortality rates for first-time mothers can range from 10% to 20%. For the cubs, the passage through this constricted canal often results in suffocation, leading to mortality rates that can exceed 60% for firstborns. While subsequent births may be easier due to permanent scarring, the process remains risky.
Cub Rearing and Survival
After the challenging birth, spotted hyena cubs are born in a den, which can be either a private burrow or a communal den shared by multiple females. Newborn cubs are precocial, meaning they are born with their eyes open, dark fur, and even some teeth. This advanced state allows for immediate, intense competition among littermates.
Aggression among cubs begins almost at birth, with siblings often fighting violently to establish dominance, sometimes leading to the death of weaker littermates. This sibling rivalry is partly fueled by the high androgen levels the cubs are exposed to in utero. Mothers provide rich milk, which has the highest protein and fat content of any terrestrial carnivore, supporting the rapid growth of their young. Cubs nurse for 12 to 18 months, reflecting prolonged dependency on maternal care. Despite this intensive care, overall cub mortality remains high, with many succumbing to birth trauma, siblicide, or other environmental factors in their early lives.