Only last week our dog chased a snake out of the garden during mid day, about same size as the one on the image and also with black lines on the body, but more grey color instead of the brown from this one.
Bugger was very fast and aggressive, snapping a few times at the dog, almost jumping through the air but our dog seemingly knew enough about snakes to keep out of the way and out of reach. Finally it disappeared in the bushes and we couldn't find it again.
According my wife it was 'very dangerous' but they say that about every snake they see, I had the impression that it was some variety of ratsnake and thus non-poisonous but I had no intention of trying to find out
Next time I keep the camera handy, but those things are really fast and usually you have enough other things on your hands. You don't see them very often, been living here now for almost 5 years and this was only the second time, suppose most of the time they get out of your way, only at night I'm a bit more careful about walking through the garden in darkness. Stamping your feet helps, they say, so far I believe them
