Adog's tail between his legs indicates that the dog is

At the point when a dog moves his tail into an upright, unbending position, it is an indication of sharpness. This happens when something startles or stimulates the dog. While some tail-swaying shows bliss, firm tail-swaying can be an indication of animosity against an interloper. A tail tucked up against a pooch's gut is an indication of dread or outrageous accommodation.