In A Nutshell
A lion’s mane isn’t just there for protection: The color indicates the male’s strength and health, letting potential mates—or rivals—know just how powerful the lion is. The darker the man, the closer the male is to the top of his game. The color can fluctuate based on how much stress or trauma the lion has experienced.
The Whole Bushel
The color of a lion’s mane directly correlates with his health, testosterone, and vigor. Mane color indicates a lion’s prowess to his fellows. The darker the mane, the more powerful the lion; when darker, the lion will scare off potential rivals or attract potential mates. A lighter mane conveys the opposite.
Mane color is not static—it changes according to the well-being of the lion. The mane will lighten if the lion has gone through a rough patch. It will darken again after he recovers, moves to more hospitable territory, or receives nourishment.
Females have shown a preference for lions with dark manes over light manes—even when the dark hair was significantly shorter. Mane length may signify lion health, like mane color, but length more than likely simply corresponds with temperature and climate. Because of this, color is more significant to females interested in mating.
Long, dark manes come at a price: They’re extraordinarily hot and heavy. In relatively cooler climates, like parts of Morocco and South Africa, males can manage bigger, darker manes. Many of the males of Tsavo, Kenya have no manes at all (and consequently, no dark hair). Lions who move to cooler climates can grow thicker, longer manes—which will just as easily shed when the lion moves somewhere warmer. Only the most biologically superior of males can afford a huge, dark mane in the hottest of climates.
The mane has also been correlated with protection, as it makes the lion look bigger to would-be attackers.
These realities don’t bode well for the protagonists of The Lion King: though Mufasa and Simba had thick, large manes, Scar’s jet-black mane would have marked him out as the most powerful lion on the planet and the rightful ruler of the pride.