Tail Positions and Movements A dog’s tail can be a strong indicator of aggressive intentions when you look at its height and the stiffness of the wag:

• Height: A tail held very high—often described as pointing up “like a flag”—signals high confidence, assertiveness, or potential aggression.

• Stiff Wagging: While people often associate wagging with happiness, an aggressive dog will typically have a stiff tail movement. This can manifest as a slow, stiff wag as the dog assesses a threat, or as short, fast, jerky twitches that indicate high, negative arousal.

Ear Positions: Ears can signal aggression in two very different ways, depending on whether the dog is acting offensively or defensively:

• Offensive Aggression: Ears that are erect and pointing forward indicate dominance, intense alertness, or an offensive threat.

• Defensive Aggression: Ears that are flattened or slicked tightly back against the head can indicate fearful or defensive aggression. Dogs often pull their ears back in this manner just before launching an attack.

The Importance of Context: Because a single signal can mean multiple things—for example, erect ears can also just mean a dog is happily alert—you must read ear and tail positions together with other holistic cues. An aggressively posturing dog will typically pair a high, stiff tail and forward ears with a stiff, frozen body, a hard, unblinking stare, raised hackles (hair standing up on the back), and bared teeth or snarling.

Furthermore, you must take a dog’s physical anatomy into account. Breeds with cropped, permanently erect, or heavily dropped ears, as well as dogs with short or docked tails, may be physically restricted and unable to clearly broadcast these specific warning signals.