Cats who are familiar and friendly with each other often have a greeting ritual. They use a similar ritual to greet their humans or other household animals. They rub their head, flank and tail against the other cat or person to exchange odours. They hold the tail straight up so that the other cat can sniff the anal glands. When stroked, cats raise their rumps even higher (almost standing on tiptoe) to invite you to sniff their anal glands!