How do posture and tail position show confidence or status in cats and dogs?

In the context of avoidance behaviour, the status and confidence of social mammals like cats and dogs can be inferred through specific physical cues, including leg extension, vertebral tonus (arched back), and tail elevation.1

Cats

A cat’s body language serves as a primary indicator of its internal state:
* Confidence: Holding the tail erect generally signals that a cat is feeling calm and confident, often serving as a friendly greeting.2
* Status and Threat: To appear larger and more ferocious, a cat may arch its back and bend its tail into an upside-down U. Conversely, a cat signaling fear, submission, or defeat will crouch low to the ground, flatten its ears, and tuck its tail between its hind legs.2

Dogs

For dogs, posture and tail position are essential tools for social interaction and communication:3
* Confidence and Aggression: An aggressive dog may display high status or dominance by holding its tail high, often wagging only the tip.3
* Submission: A submissive or fearful dog typically adopts a low posture, holding its tail low and often wagging it stiffly.3

When an animal perceives a threat from which there is no escape, it may move away from these confident postures toward general motor inhibition or freezing.1