quite right…I’d think that the bigger question would be what does.
No, but now I feel really stupid the way you asked that question. I’m going to have to find some cats to watch to see how they greet each other.
Usually they hunker down and hiss or growl warnings, if they’re not housemates. More usually they make a point of avoiding each other if they’re not bent on asserting dominance.
If they’re housemates on good terms, they might touch noses or butt heads or groom each other. Stuff like that. Sometimes there’s no discernible greeting at all. “Oh, you’re here. lies his head back down to snooze some more”
Yes, my cats sniff each other’s bottoms regularly.
I think rather than a “hug”, it’s part of how they identify each other.
I’d agree with the identification part, but I have to say I don’t recall ever seeing a habit of buttsniffing-as-greeting among cats. Maybe I just don’t get the right ones.
“So… whatcha been up to?.. mmm… hey, where’d you get the fieldmouse?.. hmmm… oh, man… you mean the humans let you in the house lst night???.. i gotta get me some of that BlueJay… mmmmm… oooh, man… you need to quit getting into the milk… that’s just not right!.. whew! …”
I wonder if this is a numbers thing? Maybe with just, say, 2 cats in the house,
they don’t need to bother with identification? There was a time when we only
had 2 cats in the house, but I don’t remember it…
Female cats don’t do this. Or not the female pussycats I’ve seen. Damn tomcats stick their noses into everything, so it wouldn’t surprise me at all.
Couple of professional perspectives if I may be indulged…
1st The keester sniffiing in dogs is for identification. More of a “glad to meet you” handshake than a hug. They’re smelling the secretions of the anal glands. These are anatomically equivalent to the glands that skunks squirt you with.
2nd Chas, have you considered surgery for your kitty’s thyroid tumor? Scalpel blades are all natural and have no side effects. 
Doc
We have 4 queens and a tom. They all do it.
Doc J, when they’re marking in the wild, do cats use the anal sacs for scent marking?
I think dogs sniff nether regions; cats touch noses.
That’s the view from here. Further investigation sort of, um, worries me.
T
Well, our cats seem to think that a little tush sniffing is normal… I’ve always thought it was kind of like reading the news.
We currently are owned by a low 6. It has sometimes been more than double that. Butt sniffing, though not as invasive as the doggie version, definitely is a daily occurrence.
We only have one cat so I don’t know about any cat-to-cat relations. But my cat only touches my nose with hers when she wants attention and affection
Our cats do both but not serially.
This was a great thread. It sort of flared up and then settled down. Like a surge of gas after a heavy meal.
My cats are all pretty small. I make them run a treadmill.
It did, at that.
What can I say? I’ve lived with cats - and in multiples up to four from time to time - all my life, and I’ve honestly never seen buttsniffing-as-greeting.
Y’all just have seriously trashy cats. 
..