Both Eastern gorillas have longer hair than Western gorillas. In Eastern gorillas both sexes and all age classes have hair that is generally black. Longer, darker hair may occur in response to the colder conditions experienced by gorillas living at higher altitudes. Western gorilla females and immatures are covered in relatively dense, moderate length hair. As with all gorillas, the cheeks and nose are hairless, but adult females also lack hair on the chest. Hair colour varies in shade but usually contains chestnut tones. The head is often slightly more red than the rest of the pelage.