Well they SHOULDN'T be able to...

...because due to some strange trait of rat physiology, they can't burp or vomit. What goes down doesn't come up again! This is why you shouldn't feed them any fizzy drinks, cos they can't get rid of the gas. So if this is true, I wouldn't have thought they'd be able to hiccup either.

But I know what you're talking about - my rats do it occasionally sometimes as well. I don't know what causes it, but there are lots of knowledgeable types around here, hopefully someone will know!