There are two reasons why lions have manes. The first is as a visual signal, even from a distance, that a male lion has status and is intimidating. The second reason is as a form of protection to the head and neck region during fights.

A ‘WOW’ lion mane. Photo in public domain or fair use.
There is possibly a third reason which is worth mentioning. A darker mane appears to be more attractive to female lions. In this case the mane serves as a sexual signal of strength and desirability.
The distinctive lion mane can be yellow, brown or reddish brown and it darkens with age. As young males mature they grow a mane usually at around 3 1/2 years of age.
The growth rate varies with each individual. Some male lions have a short rough at the age of four years while others have a heavy mane at that age.
Lion Strut
The mane comes in all sizes but they generally increase in length and thickness as the animal becomes older. They make the adult male look impressive and…
“…serve as a conspicuous visual signal. In open habitat a mane can be seen at some distance. With his mane, combined with a stiff-legged, tail-up display posture that Jonathan kingdon calls the ‘lion strut’, a male lion presents an identifiable and intimidating figure even at a distance”.
The quote above is from East African Mammals: An atlas of evolution in Africa Vol. 3A, Carnivores. Chicago: University of Chicago Press.
It appears that lions can distinguish male lions from the characteristics of their mane. Certainly, human biologists can do this.
Schaller G.B. in his 1972 study, The Serengeti Lion (Chicago: University of Chicago Press) writes:
“The dense mat of hair absorbs blows and harmlessly tangles claws in a part of the body toward which most social contact is directed; bites to may leave an opponent with a mouthful of hair rather than skin”.
ASSOCIATED: DETAILED INFORMATION ABOUT THE LION MANE.
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