Lazy,
I've not seen a rattlesnake back there yet. I've killed two water moccasins/cotton mouths,however. And from counting snake skins, I know there is at least one more calling our yard "home".
I wouldn't have killed them, but I've got two dachsunds who would have got themselves in trouble if the had spotted the snakes first.
We have a nimbler of snake eating birds that hang around the house, too. They help with some of the lesser snakes.
We are fortunate in that our back yard buts up against somebody else's small ranch. They only mow twice a year, and there are lots of wildflowers, so we have plenty of forage for the bees.