Actually, what I've always noticed about them is that they don't seem to have a clue how small they are. They'll run right up to a German Shepherd or Great Dane or Rottweiler and start in with assertive and even aggressive barking and nipping. One of my vets has the most awesome picture in her office of a Great Dane and a Chihuahua. Both are on leashes, but the Chihuahua -- with teeth bared -- is straining against the leash to try to get at the Dane and show it who's alpha dog. The Dane, on the other hand, has it's leash drooping loosely and is looking at the crazed Chihuahua like "Hmmmm, I wonder what that little insect is so excited about".
I knew Chihuahuas and other micro-dogs could convince them*selves* that they're full-sized dogs. Had no idea they could convince a mountain lion.
Micro-dogs, lol.
I have an English Mastiff (300 lb) who is terrified of my 4lb Toy Fox Terrier.
Ol' mountain lion was convinced she didn't have a chance with a pack of three of them. Those guys are fast. Chihuahuas are to dogs what piranhas are to fish!
The mountain lion, as a solitary hunter, can't afford to get injured, so it will usually run if it thinks it could get harmed. It likely ran into the garage and found itself trapped and the little dogs prevented it from getting out without injury.
If the chihuahuas had headed in to attack him, he likely would have killed them all and made his escape, but as they hung out in the access point, he couldn't chance it.