Here are some of the fastest animals in the animal world.As you read about them，remember that the top speed of human runners is 20 to 25 miles an hour.And the fastest human runners can only run at this speed for a few hundred yards(码)．

　　Heavy people do not run very fast.But some heavy animals can run at amazing speed.Black rhinos can run at a speed of almost 30 miles an hour，even though they may weigh over 3,500 pounds.

　　Cheetahs are the fastest land mammals(哺乳动物) over short distances(距离)．They can run at a speed of over 70 miles an hour.But they get tired quickly and usually stop after a few hundred yards.

　　Pronghorn antelopes are the fastest land mammals over long distances.They can run at a speed of 35 miles an hour for many miles.Their top speed is probably more than 50 miles an hour.

Hummingbirds are the smallest birds.But they move their wings(翅膀) faster than other birds.Some of them beat their wings 4,500 times a minute.