The Arizona Diamond Rattlesnake, or the western diamondback rattlesnake, is a venomous rattlesnake species found in the United States and Mexico. According to wikipedia, it is responsible for the majority of snakebite fatalities in northern Mexico and the second-greatest number in the U.S.
This specimen was found half way down a trail in the Grand Canyon, just on the side of the trail. Hundreds of tourists were just meandering past like it was nothing.
The color pattern generally consists of a dusty-looking gray-brown ground color, but it may also be pinkish-brown, brick red, yellowish, pinkish, or chalky white. This ground color is overlaid dorsally with a series of 24-25 dorsal body blotches that are dark gray-brown to brown in color.