the "traditional" macro lens for technical shots of snakes is a 90mm prime - but with today's aps-c sensors, that needs to be more like a 60mm lens. I know a lot of people who have tried to use 100mm macros for snakes and have a hard time because they have to shoot from six feet away to get more than just the snake's head in the frame.

I can't wait to see your local stuff, I haven't been to oz but I do have plans to spend a month there next spring (november, maybe).