A wagging tail means a variety of things depending on the animal and the circumstance. For instance, a cat might wag its tail when it’s annoyed or uncomfortable, while a dog might do so to express excitement and happiness. When a squirrel wags its tail, it usually means the animal feels upset in some way. Squirrels often wag their tails to communicate a message. This might be a warning to other squirrels about potential predators or other dangers. On the other hand, it could also point to feelings of fear or even frustration. Odds are, if a squirrel is wagging or twitching its tail near you, you should probably back off.