I am marlborough in nth qld working and have seen two black snakes both with bright yellow bellies and with a white/grey head. One i found dead and the other very much alive while out jogging. both were decent size snakes. The first i thought was a red belly black but after seeing the dead one i gather they are both the same and have a yellow belly..will try and get a photo of the dead one this arvo but can someone tell me what they are.. and they are not tree snakes lol ( google found under yellow belly black)