The lion is a species in the Felidae family and a member of the genus Panthera. It has been listed as Vulnerable on the IUCN Red List since 1996, as populations in African range countries declined by about 43% since the early 1990s. Lion populations are untenable outside designated protected areas. Although the cause of the decline is not fully understood, habitat loss and conflicts with humans are the greatest causes of concern. The West African lion population is listed as Critically Endangered since 2016. The only lion population in Asia survives in and around India's Gir Forest National Park and is listed as Endangered since 1986.
The mane of male lions starts growing when they are about one year old. Mane colour varies, and darkens with age. Research results indicate that environmental factors such as average ambient temperature influence the mane's colour and size. 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, colour, and size of the mane is associated with genetic precondition, sexual maturity, climate, and testosterone production; the rule of thumb is the darker and fuller the mane, the healthier the lion. Female lions favour males as mates with the dense, dark manes.