I don't know about Yosemite rattlesnakes being "mellow" - this seems naive to me. My boyfriend was bitten by a rattlesnake and he nearly died. This was hiking in the LA area in early Feb. last year. The snake bit him twice on the shin and pumped a LOT of venom in. He was airlifted and to the hospital within an hour, got lots of antivenin over the course of several days, but it took overby mytwocents - General Discussion