What does it mean when a cat's tail is arched?

When a cat arches its tail, it's displaying a distinct body language that communicates its emotional state. An arched tail can indicate the following:

Fear or Startlement
One of the most common reasons for a cat to arch its tail is in response to sudden fear or startlement. This is often accompanied by the cat's back arching and its fur standing on end (piloerection), making the cat appear larger. This is a defensive posture meant to make the cat appear bigger and more intimidating to potential threats.

Playfulness
Kittens and young cats, in particular, might arch their tails during play. This can be seen when they're "ambushing" toys, other cats, or even your feet. In this context, the arched tail is part of a playful, exaggerated hunting posture.

Aggression
In some cases, an arched tail, especially when combined with other signs like hissing, growling, and flattened ears, can indicate aggression. The cat might be feeling threatened and is signaling that it's ready to defend itself if necessary.

Excitement
Some cats might arch their tails when they're particularly excited or stimulated, especially if something in their environment has captured their attention.

Greeting
In rare cases, some cats might arch their tails as part of a greeting ritual, especially if they're feeling particularly affectionate or excited to see someone.

As with all feline body language, it's essential to consider the broader context when interpreting an arched tail. Observing the cat's overall posture, facial expressions, vocalizations, and the situation will provide a clearer understanding of what the cat is feeling or trying to communicate.

If a cat frequently displays an arched tail in situations where there's no apparent threat or stimulus, and especially if it's accompanied by other signs of stress or discomfort, it might be worth consulting with a veterinarian or feline behaviorist to ensure there aren't underlying health or behavioral issues.