A great book I have been reading about creatures that live around oak trees in California says that ground squirrels have long been the staple of the rattlesnake diet. Over time, the squirrels evolved to have higher resistance to the rattlesnake venom, and then, in coevolutionary fashion, the snakes with less poisonous venom starved before leaving offspring. The surviving snakes had stronger venom and left offspring with that trait. In turn, the more resistant squirrels left more offspring. The circle has continued for a long time, making snakes more venomous. If our ancestors had been snake food, then we too would have more natural resistance.
The first rattlesnake I saw in the San Jacintos crossed the Devil Slide trail one afternoon as I was coming down. It was not more than a 100 feet in elevation below saddle junction. The second one that I remember coiled up and rattled at me, only about a foot away from my leg, while hiking on the PCT on the desert divide. I remember another at a switchback on the PCT north of saddle junction, at about 8400 feet. There have been others, but after encountering so many, the details are blurry.
I do see them more often at lower elevations. I remember several within a few minutes at lower elevations on the snow creek trail.
BTW, I have never personally seen poison oak above about 4500 feet in the San Jacintos. I know of a botanist who has unexpected found it above 6000 feet, where it really should not be. I guess nature does not respect boundaries.
