A truckie going from Melbourne to Perth picks up a hitch-hiker. After a while the hitch-hiker says he's tired and lays down in the truck's "sleeper" compartment for a rest.
A while later the hitch-hiker is woken up by the noise of the truck running over something: "BASH!, BASH!, BASH!".
"What's all the racket?" he asks the driver.
"Oh, I just hit an Abo."
"But, what was all that other noise?"
"Well, I had to go over two fences to get the bastard."