The lion's mane is the most recognizable feature of the species.It starts growing when lions are about a year old. Mane color varies and darkens with age; research shows its color and size are influenced by environmental factors such as average ambient temperature.

Mane length apparently signals fighting success in male–male relationships; darker-maned individuals may have longer reproductive lives and higher offspring survival, although they suffer in the hottest months of the year. The presence, absence, color and size of the mane are associated with genetic precondition, sexual maturity, climate and testosterone production; the rule of thumb is that a darker, fuller mane indicates a healthier animal.