Logan Cates (Rory Calhoun) is a cowboy drifter who's riding to Yuma when he is attacked by some renegade Apache Indians. He shoots and kills some of them and the remaining two ride away. We see one Indian ride over a hill, then we see a rattlesnake crawling on for a few seconds, then we see the second Indian riding up the hill when his horse is frightened by the rattlesnake and throws the Apache to the ground. Cates jumps the Apache and then they roll around wrestling in the dirt with knives drawn until, of course, Cates wins the fight.

We don't see enough of the rattlesnake to identify the species, but it's probably a very dark Southern Pacific Rattlesnake from Southern California since that's where the movie was filmed.