This is the first time that I have seen this sort of behavior. The video (animated .gif file, actually) is a bit peculiar and I hope it plays for you. Below the video is a still image in case the video disappears. If you click the object in the middle you get music and …
The cat tail up position in relation to a cat meeting another cat is a communication signal – a piece of body language – which says: “I am friendly and I accept my social status”. So, it is more likely to be initiated by a cat of lower status to a cat of higher …
Note: Some older videos on this page were hosted on Vimeo. That account has now been retired, so a few video blocks may appear blank. Thanks for understanding — there’s still plenty of cat content to enjoy!