The term "maneless lion" or "scanty mane lion" often refers to a male lion without a mane, or with a weak one.
The purpose of the mane is thought to signal the fitness of males to females. Experts disagree as to whether or not the mane defends the male lion's throat in confrontations.
Although lions are known for their mane, not all males have one. This might be because of a polymorphism within males.