What makes a rattlesnake's rattle...rattle?

The sound of a rattler's raspy buzz fills most hikers with dread -- and for good reason. Rattlesnakes, who belong to the pit viper family, are known for beating the pointy tips of their tails against the ground to ward off enemies.

A rattlesnake baby is born with what's called a "pre-button" at the end of its tail. When the rattlesnake sheds its skin (which happens about 10 days after birth and every few months thereafter), the skin gets caught on the pre-button and a button is formed. At the second shed, the first segment is formed and can now rattle slightly against the button. Each time the snake sheds, a new segment is added and the rattle gets longer and louder. The segments knocking against each other create the sound and allow a rattlesnake to rattle its tail in the air rather than beat it against the ground.

The rattle can be loud: its frequency can peak at 5,000 to 8,000 hertz (which is roughly equivalent to an ambulance siren) and at a loudness of 60-80 decibels from a distance of one meter.

However, as a rattlesnake gets older, the outer segments of the rattle sometimes become brittle and fall off. That's why you can never tell the age of a snake by the size of its rattle. Not that you were eager to examine them up close anyway.