Even the poisonous snakes are helpful to your environment... They just carry some added risk.
Funny Story, We have a large Black Racer that lives under the porch and kills lots of rodents. Sometimes I see it sunning and I swear it has bulges from multiple varmints it has eaten recently. We also have an open carport and a Mazda Miata that lives its summer with the top down. One day I jump in the Miata to run to the parts store and about a mile from the house I hear hissing and see the snake peeking down from under the dashboard looking up at me! I pulled off of the road immediately and tried to chase it out of the car, but I only chase it further up into the dash. After an hour of waiting I drive the car home looking the whole time for the snake to slither out.... I then left the car under the carport for a week with the doors open. Haven't seen the snake since, so I'm not sure what happened to him, but he scared the crap out of me!
However, after having the rodents eat the wiring out of the dash of my TC18, I'd rather have the snakes around than the rodents....
