If out hiking you could come across a Rattlesnake sunning itself on a rock similar to what this snake is doing. It has been noticed that more and more of the Rattlesnakes in the western part of Texas will not rattle before striking but many of the adults will not necessarily inject a full dose of venom when biting an adult human. See they have the ability to control the amount of venom that they wish to inject into their prey and quite often they won't waste their venom stores on a large prey that they don't consider to be a meal for them. Now what will happen is that the rattlesnakes on a hotter day will go under a bush or mesquite tree to get out of the sun and then a cow will go into that same shade area without realizing that the snake is there. The snake bites the cow in the neck area, the neck swells shutting off the windpipe of the cow and the cow will die from suffocation which is why many ranchers will try to keep the rattlesnake population to a minimum.