I was walking out in the middle of the desert with my dogs on state-trust land (basically untouched desert with a few dirt trails). I took off their leashes so they can run around happily. It's completely silent; no cars, no houses, nothing. Without any warning whatsoever, I hear a very abrupt and VERY loud hissing noise at my feet. I look down to see I'm standing ON one of these
http://upload.wikimedia.org/wikipedia/commons/e/e3/Crotalus_atrox_CDC.png, half coiled, sitting right there in the middle of a dirt trail probably soaking up some sun.
A Western Diamondback Rattlesnake, responsible for the most snake-bite fatalities in Mexico, and the second greatest in the USA. They are one of the more aggressive species found in North America because they rarely back away from confrontation. Most of the toxin released is proteolytic like all other American pit vipers. Proteolytic venoms are, in fact, advanced and concentrated fluids that destroy tissues and other cells through intramolecular digestion. A few toxic effects include: cytotoxic (destroys cells), hemotoxic (destroys red blood cells), myotoxic (causes paralysis and muscle destruction), hemorrhagic (causes persistent bleeding). Smaller amounts of neurotoxins are also present.
After being shocked in place for a split second, my instinct kicked it, causing me to scream like a little girl while jumping back 5 feet. Very surprisingly, it didn't strike. These snakes are very well known to strike even if you're 3-5 feet away, let alone standing on it. Not to mention I was alone, had left my cell phone at home, and was a 10 minute walk away from any paved road.
Looking back on it, it was a hell of an adrenaline rush and I'm glad it happened. Now I know to stay alert and look more closely where I step while walking in the middle of the desert. I'm planning on getting my dogs snake trained as well.