Cheetah hair (Acinonyx jubatus), coloured scanning electron micrograph (SEM). Although the cheetah is similar to the domestic cat (Felis domesticus) and is of the family felidae, the hair is markedly different. The domestic cat hair scales are much more pointed in shape and evenly spaced. The cheetah is the fastest land animal running at speeds of up to 75mph/120kmh. It can accelerate at an incredible 0-60 in 3 seconds, faster than most sports cars. Unlike true big cats the cheetah does not roar but it does purr as it inhales and exhales just like the domestic cat. Big cats on the other hand, purr only when they exhale. Cheetahs have a Red List status of \Vulnerable\" as assessed in 2008, with a total population estimated at no more than 15, 000 worldwide (2008) with numbers falling yearly. Magnification x422 at 10cm wide."