The Western Diamondback is a perennial favorite. (Well, they are my favorite, anyway.) (Several people have even seen them mating in the canyon.) The Black-tailed is also common. The Tiger is not seen nearly as often. Note the differences between in the tail sections before the rattle - all very prominent in these great photos by Ned Harris. Western d-back: black and white rings; Black-tailed: entirely black; Tiger: neither. Regardless of type, though, rattlesnakes don't always rattle before striking. Although they don't 'want' to waste venom on you (you are way too big to eat), if you step on or startle one, s/he will likely strike first and beg your pardon later (or not bother with the latter). Look before you put your hands and feet (and those of your companions) into holes, shady spots, or other good rattlesnake hideouts. If you get bitten, call 911 immediately. Don't wait. Venom digests tissue and doesn't discriminate between rabbits and humans.