Pronghorn
Description
The pronghorn is the fastest land mammal in the Western Hemisphere, being built for maximum predator evasion through running. The top speed is very hard to measure accurately and varies between individuals; it can run 35 mph for 4 mi (56 km/h for 6 km), 42 mph for 1 mi (67 km/h for 1.6 km), and 55 mph for 0.5 mi (88.5 km/h for 0.8 km). While it is often cited as the second-fastest land animal, second only to the African cheetah, it can sustain high speeds longer than cheetahs. University of Idaho zoologist John Byers has suggested the pronghorn evolved its running ability to escape from now-extinct predators such as the American cheetah, since its speed greatly exceeds that of all extant North American predators. Compared to its body size, the pronghorn has a large windpipe, heart, and lungs to allow it to take in large amounts of air when running. Additionally, pronghorn hooves have two long, cushioned, pointed toes which help absorb shock when running at high speeds. They also have an extremely light bone structure and hollow hair.
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