The silent shake
Rattlesnakes didn’t always have rattles. Before developing their characteristic warning signal, scientists believe they would still shake their tails when threatened. Whether this was a sign of stress or an attempt to scare away other animals with the movement alone, the action worked in letting threatening animals know that the snake was about to attack. How the rattle evolved is less well known, but some think that a genetic mutation meant some snakes were more likely to leave excess skin behind at the end of their tails during shedding. As they continued to shake their tails, the outcome was a noisy deterrent to other species. Over time this advantage kept the noisier snakes alive. These rattles would then have evolved further to become the more intricate and impressive structures they are today.