Prairie Rattlesnake

On October 17 it was a cool 62 degrees F and we were sailing down a dirt road headed east in extreme eastern Colorado or extreme western Kansas on our way to Mount Sunflower, the high point of Kansas. I was going 50 mph or so and noticed a large greenish rattlesnake on the dirt road. I stopped as quickly as I could, did a three-point turn, and back-tracked to the snake, still on the dirt road. I couldn't believe it was out in such cool weather, although it was sunny. 

When I first saw it it was stretched out, but it pretty quickly got in a coiled defensive posture where it stayed. While we were looking at it and taking photos a huge tractor came by. I wanted to move it off the road so that it would not end up as road kill, but couldn't find anything long enough to allow me to safely move it, so we left it where it was and moved on. 

It was a prairie rattlesnake, also known as a Great Plains rattlesnake, which is a subspecies of the western rattlesnake. The maximum recorded size is 5 feet, but they commonly get more than 3.3 feet. I think this one was that big, and quite fat. It is usually a greenish gray, olive green or greenish brown. I would characterize this one as greenish brown. I was quite excited as this is the first rattlesnake of this species that I've seen. 

In Kansas, they are only found in the western half. They have a pit on each side of the head, between and slightly below the eye and the nostril. They have a large scale over each eye. 

Distribution of the prairie rattlesnake (from Wikipedia).