The Cheetah is a creature built for speed: she can accelerate four times faster than a human and attain speeds of up to 120 km/h, making her the fastest land animal in the world. Her claws are semi retractable, and the pads of her feet are ridged, allowing her greater traction. She uses her tail as a rudder, allowing her to turn sharply and flank her intended prey. To aid her breathing, she has large nostrils and enlarged lung and heartthat help circulate oxygen efficiently. For all her adaptations, however, the Cheetah is vulnerable to extinction. At some point in the past her species "bottlenecked" after the last ice age, losing a great deal of genetic variability, and suffering a decreased sperm count. This, combined with a cub mortality rate of up to 90%, means the future of this feline is by no means assured.