The cheetah is the fastest land animal on earth, capable of accelerating from 0 to 100 kilometres per hour in just three seconds. This extraordinary speed comes at a cost -- the cheetah is a fragile predator, with a lightweight frame, reduced jaw size, and claws that cannot fully retract, all adaptations for speed that sacrifice the fighting ability possessed by other big cats.
Cheetahs are uniquely adapted for speed. Their spine is unusually flexible, acting like a spring that flexes and extends during a chase. Their long tail provides balance during high-speed turns. Their black "tear lines" -- the dark streaks running from eyes to mouth -- are thought to reduce glare and help them focus on prey during daylight hunts.
The species has undergone catastrophic declines -- from perhaps 100,000 individuals in 1900 to roughly 7,000 today. The primary driver has been habitat loss as African rangelands are converted to agriculture and settlements. Cheetahs require large territories -- up to 1,500 square kilometres for a male coalition -- and are extremely sensitive to habitat fragmentation.
A unique aspect of cheetah biology is their genetic uniformity. The entire global cheetah population descends from a bottleneck roughly 10,000 years ago, making them one of the most genetically similar mammalian species to their own kind. This makes them particularly vulnerable to disease.