More Fun with Snakes

Sedona is doing quite well. She acts as if nothing happened at all. The swelling had gone down a bit but remains rock hard. The wound is not currently enlarging.
The following story happened about a month ago. It was a hot day and I was in the house watching a DVD from Netflix. I finished and when I turned off the television, I heard a noise. It was a noise I did not recognize. I followed it to the front of the house and realized it was coming from the cat patio. About the time I looked out the window I knew what it was--a rattlesnake--and a very large one and very annoyed from the sound of it. The cats were circling in a semi-circle around a corner under the steps. I was able to safely open the door and snatch up each cat and toss them inside. I got a look at the snake under the steps. Oh my--all coiled up and rattling loudly and just huge. It was as big around as my upper arm, probably a 6 footer.
Now what?! The only way I could shoot him would be to lie down on the concrete and aim under the steps. I was not about to lie down anywhere in the vicinity of that snake. By the time I finished dithering around and looked again, the snake was gone. I suspect that as soon as I removed the cats, the snake got out of there fast. My theory is that while the cats were asleep on the table, the snake came onto the patio to be on the cooler concrete. When the cats woke up and jumped on the steps, it awoke and annoyed the snake who then started rattling which made the cats curious, albeit cautious, and the circling predators annoyed the snake further. The snake was in a corner with on where to go and the cats were not going to leave. I broke the stalemate.

My question--Sedona does not know about snakes. Many dogs have to have snake training to beware snakes. So, how did the cats know? They are house cats and have been so all their lives. Do other cats know? Or was I just lucky with my cats? When I ask them, they just give me a look!
I have more snake stories but I also have customers in my store who require my attention so I'll get back to this Friday.