Why do cats land on their feet?

When a cat falls, an automatic righting reflex kicks in, usually by about three to four weeks of age. Using their inner-ear balance system to sense which way is down, cats bend at the middle and rotate the front and back halves of the body in sequence, conserving angular momentum to flip upright. Their unusually flexible backbone and lack of a rigid collarbone allow the twist, and they spread their legs to slow the fall. Even so, falls can still injure cats, so the reflex is not a guarantee of safety.