If you are going to spend much time hiking in rattlesnake country you might want to check out a rattlesnake aversion course for your dog. I'm sure you can find one offered in Texas; check with a few vets and I expect you'll find one. I live in rural SE Arizona and have a lot of rattlers on our property. I have put our golden retriever Rosie through aversion courses twice: now she won't get within ten feet of a rattler but she will let us know by her behavior that one is around. I'm pretty sure it is a scent thing because often the snakes are/were pretty well hidden.

Around here the cost of a typical course of anti-venom for a snakebiten dog is about $3000. An aversion course costs about $50.

It would be nice if bear aversion courses were offered too but I don't think they are. I don't worry too much about cougars though they are not uncommon around here; we'll hear about an occasional sighting from neighbors. Bobcats too.
May I walk in beauty.