My mother swore that you could tell how near a cat was to full of food or water by the position of its tail. She said when the cat first comes to the bowl, its tail will be off the floor. But as it gets closer and closer to full, the tail will slowly come down to the floor.
Don't think that works on my cats...but then, when are they ever seriously hungry or thirsty?
Don't think that works on my cats...but then, when are they ever seriously hungry or thirsty?