Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
After 3 years in prison Robert Wagner is released and goes to visit his now-dead father's abandoned ranch house which is falling apart. To show us just how abandoned and miserable it is, he sees a Gila Monster standing on a bench just outside the house. It's doubtful that a Gila Monster is capable of climbing that high up a wooden bench, but this is not reality, it's a movie. Earlier he shot a rattlesnake with another man's gun, but he isn't carrying a gun here, and that's probably the only reason he leaves the lizard alone. It's a little hard to see, but it looks like they used a live Reticulated Gila Monster in the scene.