A "hair helmet" is a thick, protective layer of hair that covers the head like a helmet. In the animal kingdom, the hair helmet is commonly found in mammals, such as the American bison and the Tibetan yak, providing insulation against extreme cold and protection from predators.
Its relevance lies in its ability to shield the wearer from harsh environmental conditions, both hot and cold. Additionally, hair helmets enhance sensory capabilities, allowing certain animals to detect predators or prey from afar. Historically, humans utilized hair helmets, particularly during ancient battles, for protection against head injuries.