Cat show you their butt as a way of telling you that they are comfortable with you.
Image may be NSFW.
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Because nothing says “let’s be friends” like “hey, do you wanna see my butt?” Tail sniffing behavior is normal between cats. In fact, when two cats greet each other, they usually do so by sniffing each other’s nether regions, as each cat’s signature scent is found there. Cats that keep their tail down “might be compared to a shy person hiding his/her face.”
A raised tail says “I mean no treat.” When your cat decides that you’re worthy of having its butt in your face, it does not expect you to sniff (thankfully). Cats have a way of realizing that you are not a feline, and will be content with a friendly pet or scratch.
