It's either snakes or rats and mice, take your pick. I personally pick snakes....as long as they are not venomous. The rattlers and moccasins get destroyed, don't see any other choice as long as i have dogs.
If I can catch one somewhere else, I'll bring it home, I've relocated many here. I have found nests with eggs not far from the house.
Hopefully you have more around and now you know.
I suspect a large colubrid will eat 30-50 rodents a year, about one a week, less in the winter, more in the summer, depending on the size of the rodent. So if their not around ....do the math.
just a guess