Female lions, known as lionesses, do not possess the prominent manes characteristic of adult male lions. This visible difference is a typical example of sexual dimorphism, where distinct physical traits exist between males and females of the same species.
Purpose of the Male Lion’s Mane
The male lion’s mane serves multiple biological and social functions within the pride. Its primary purpose is sexual selection, as the mane acts as a visual signal to attract mates. Female lions often prefer males with darker, more impressive manes, indicating genetic fitness, overall health, and protection ability.
Beyond attracting females, the mane also plays a role in establishing dominance among males. Males with more substantial manes are often perceived as more formidable leaders, deterring challenges over territory or mates. This visual display exaggerates the head and neck size, making the male appear larger. Additionally, the thick hair may offer some protection during physical confrontations, absorbing impacts from blows and bites, though this is a secondary benefit.
Absence of Manes in Female Lions
The absence of a mane in female lions is primarily due to hormonal differences, specifically lower testosterone levels. Testosterone is the hormone responsible for stimulating mane growth in male lions as they reach sexual maturity. While lionesses do produce testosterone, the amount is typically insufficient to trigger extensive mane development.
Furthermore, the lack of a mane in females is linked to their roles within the pride. Lionesses are the primary hunters, and a large, cumbersome mane would hinder their agility and stealth. A sleek, unencumbered body allows for efficient movement and better camouflage. A thick mane would also increase body temperature, which would be disadvantageous in the hot African climate, potentially impacting strenuous activities like hunting.
Unusual Mane Growth in Females
Although rare, female lions have developed mane-like features. These unusual occurrences are typically linked to hormonal imbalances, often involving elevated levels of androgens such as testosterone, androstenedione, or cortisol. Such surges can trigger male secondary sexual characteristics. These imbalances can sometimes stem from underlying conditions like benign tumors on the adrenal glands or ovaries.
For example, in 2016, researchers observed five lionesses in Botswana’s Okavango Delta with manes and male-like behaviors, including increased roaring and scent-marking. One well-known case involved Bridget, an 18-year-old lioness at the Oklahoma City Zoo, who sprouted a mini-mane due to elevated cortisol and androstenedione levels, likely caused by a benign adrenal tumor. While maned lionesses may display masculine behaviors, their reproductive capacity can be affected, with some mating but not conceiving, suggesting potential infertility linked to the hormonal changes.