The lion is a muscular, deep-chested cat with a short, rounded head, a reduced neck and round ears, and a hairy tuft at the end of its tail. Male lions have a prominent mane, which is the most recognizable feature of the species. It starts growing when lions are about a year old. Mane color varies and darkens with age; research shows its colour and size are influenced by environmental factors such as average ambient temperature.
Lions spend much of their time resting; they are inactive for about 20 hours per day.