The Righting Reflex

Drop a cat from a reasonable height, and it will almost always land on its feet. This ability, known as the righting reflex, begins the instant a fall starts. The cat's vestibular system, a set of fluid-filled canals in the inner ear, continuously tracks the body's orientation relative to gravity, and it signals the brain within milliseconds of the fall beginning. What follows is a rapid sequence of coordinated movements rather than a single motion. Because a cat's spine is unusually flexible and it has no rigid collarbone to restrict its shoulders, it can rotate the front half of its body toward the ground while the rear half briefly rotates in the opposite direction, conserving the animal's overall angular momentum without needing to push off any surface. Once the front half has turned, the rear half catches up, and the whole rotation is typically complete in well under a second. As the cat approaches the ground, it also extends its legs and arches its back slightly, a posture that increases air resistance and softens the impact. The reflex is remarkably reliable, but it depends on having enough time and distance to complete: cats dropped from very low heights, below roughly thirty centimeters, often cannot finish rotating before they land.