Darker, fuller manes indicate a healthy lion with plenty of testosterone. This makes him catnip to the ladies, but also tells potential rivals to beware; he won’t back down from a fight. Mane length is also a signal to other lions of fighting success (presumably manes are damaged in these challenges).

Black manes are perhaps the most telling status-symbol; manes darken with age, and thick dark hair indicates a well-fed lion. That means a black-maned lion is likely in his prime, eating well, and getting plenty of lovin’ from the ladies. Who would want to mess with that?