Why do male lions have manes? [VID: Why do male lions have manes? When a male lion reaches sexual maturity, he starts to grow a thick mane. The hormone testosterone is responsible for this process. Neutered males usually lose their manes entirely. Research shows that females are attracted to males with larger, darker manes. It is believed that manes are a signal of sexual fitness and status. A male's mane serves as a form of display, similar to a peacock's tail. It is also believed that the mane