GlennT,
We've got a good population of your Texas rat snakes here in SE Louisiana. I've run across a 5+ footer or two with lots of lumps along their lengths, so I guess they are feeding on rats & mice pretty well. They are also EXCELLENT climbers. My wife was working in our barn one afternoon & looked up to see a snake in the rafters, entering the loft. Didn't do her much good to call me at work, 50 miles away! I told her to be thankful we had a barnsnake to keep the rats out of her tack room.
Unfortunately, we've also had them in our garage, & I'm pretty sure they've been in my attic, although I'm not telling my wife. Neither of us want to move back to town.
By the way, a barn cat adopted us about a year & a half ago - - that's eliminated the rat problem, & we haven't seen a snake out there in some time. Now if I could just get him to take up residence in the garage.
In 9+ years here in the sticks, I've only seen two poisonous snakes, both copperheads. And they are the only snakes I've killed. The others I just flip into the woods - - although I know they come back as soon as I'm out of sight.