Squirrels shake their tails for several reasons related to communication and survival. They use tail shaking to signal warnings to other squirrels about nearby predators, to show frustration or alertness, and sometimes as part of mating behavior to attract potential mates. Tail flicking can also serve to confuse predators or make the squirrel appear larger and more threatening. Additionally, it helps squirrels protect themselves by signaling they are aware of danger and ready to flee if necessary.