Like a cheetah’s spots or a zebra’s stripes, a male lion’s mane is perhaps the animal's most iconic feature. But there is actually a significant amount of variation in the king of the jungle's 'do, from voluminous golden locks to none at all. 

For years, scientists identified different lion species and subspecies, in part, by the length of their locks. They believed that mane length was a genetic characteristic, passed down from generation to generation. 

But a study by Bruce Patterson, the curator of mammals at the Field Museum in Chicago, reveals that the length can largely be attributed to climate. According to The Field Museum, the temperature of the zoo lion's environment is responsible for up to half of the span and density of its mane. While genetics may also be a factor—some of the big cats may be predisposed to longer, more luxurious manes—temperature can cause a huge amount of variation. This means scientists may need to reevaluate some of their existing taxonomy.

Patterson studied lions at 17 zoos across the United States, recording area temperatures and the length of the hair around each mammal's neck. He found that those in colder climates had significantly longer strands than those in warmer areas. Because manes take energy to grow and maintain, lions in warmer temperatures, who don’t need the ring of hair to keep warm, simply grow smaller ones. 

While it’s relatively rare, some lions in particularly extreme heat don’t grow manes at all. In fact, Patterson’s study was inspired by two such lions—the famous Tsavo man-eaters. Back in the late 19th century, the Tsavo lions hunted and killed as many as 135 people in Tsavo, Kenya. They were eventually shot, killed, and donated to the Field Museum where, close to a century later, Patterson became transfixed by their maneless condition. 

[h/t Field Museum]