"do you really think it is fair that all the wildlife are kicked out of their habitat..."
Was your house built on a natural clearing or was it once forest and clear felled? Your not getting any sympathy for letting a couple of creatures live there. Also in the wild i'm fairly sure a dingo would make a nice meal out of mr possum.
I'm not sure how practical it is or how well they learn but a cheap electric fence worked very well with my dog. They generally only have to get zapped once or twice to learn.
