Something weird happened to one of my cats (Halle Berry) a few days ago.
I recently moved to a new apartment that is quite a lot colder than my old place, and close enough to a major highway that you sometimes can hear it.
Anyway, I was sleeping the couch since my bed isn't assembled yet and it is very cold in that bedroom, and woke up noticing that the couch was sorta vibrating. I had my ear against the pillow, and it sounded like either they were doing construction nearby using jackhammers, or there was some big diesel semi truck idling on the highway. When the noise wouldn't go away I though maybe my big subwoofer had gotten damaged during the move and was now vibrating on its own. After a few minutes, Halle who was lying near my feet moved up to lay on top of my belly, and that's when I notice the noise was coming from here. She was purring, and also vibrating, and the vibration was causing the low-frequency rumbling sound. It was strong enough that I could feel the couch vibrating. At first I though something was wrong, but by morning she was her normal self.
Anyone ever seen a cat vibrate like that? Any suggestions on what was causing it? Yes, it was cold, but not THAT cold. But could she be shivering?
And before anyone suggests, it is not just a case of enthusiastic purring. I've had cats at home my entire life, and have Hally since 2007 or so and never heard anything like that coming from a cat.