Just wanted to chime in and say that pet rabbits certainly do this, usually when they are very happy or relaxed.
I have read it but never observed it in my own rabbit, so I concluded it was an exaggeration.
OK - since the topic has moved to tickling, check out this timely story!
My dog would argue that with any wolf. I can hear the conversation;
Duncan; " You idiot, why don’t you just warm-up to these humans. They’ll give you everything".
Wolf; "But I have everything. Look here (turns to fan outspread paw across the horizon). I’ve got mountains, valleys, deer, elk, and clear streams from which to drink.
Duncan; “Ok, ok. But I’m sleeping inside on a comfy dog bed. I have my meals handed to me, no chase required. And I don’t have to ask the Alpha how much of the food I get today… it’s all MINE!”
Wolf; “yea, but i’ve got mountains and elk and water”
Duncan; “I had fried bacon and eggs this morning”.
Wolf; “howwwwwlllllll”.
Any time you try to compare animal intelligence, you run into the trouble of trying to define what intelligence is.
Obligatory Onion article: Study: Dolphins Not So Intelligent On Land