Growing up in Louisiana, I can tell you for sure. If it looks like a water moccasin, shoot. Don't worry too much about the yellow belly water snake, or whatever they think it might be. The only snake I don't mind is a king snake. I just saved one on the road today. I like those, they eat bad snakes. I will go out of my way to help a king snake. Every other snake... meet my arrow, or Ruger or mossberg or whatever it takes.
My dog got bit by a rattler 3 weeks ago. He is just now starting to look and act normal (finally doesn't have a basketball sized pouch of swollen puss on his neck). I figure the vet bill will be equal to about 200 rattler hides. I plan to get my money back on that deal...
Rat control? King snakes eat bad snakes AND RATS... and I have two boys under 12, with bows and pellet rifles. Between the king snakes I save, and the boys, there aren't too many rats around here... God willing, soon there won't be many, if any, rattlers around here either.