In 2003 did a 3 month trip around the Eastern half of Australia with my wife, 4wheeldrive and tent. We visited some friends in Queensland near Claremont, they are broad acre farmers, aside from shooting ferral pigs one of the sports the boys got into was eliminating cane toads. At that point I had never seen one, for the whole week we couldn`t find one cane toad. This area was supposedly overrun with them.
When we went further up north to catch up with more of my wife`s friends and cousins we still saw very few. During the same trip I spend a bit of time talking to rangers in different National Parks and it appears that there is a drop in numbers in Cane toads.
Keep in mind down here in Victoria, we don`t get Cane toads, so not really that familiar with them.
Things become a bit different as we left Queensland and started heading to the Northern Territory. We spend a couple of day in a fishing/camping lodge near Burketown, the name escapes me for the minute. The whole camping area was overrun with small cane toads and they were going stupid feeding on moth and any other insects. They were all small 5cm or less.
When we got to Katherine Gorge near the town Of Katherine the gorge was full of cane toads, just small ones, but they were everywhere. I had been there in 1998 when I did a motorbike trip up the center and then around West Australia and there were no cane toads anywhere.
Basically it appears that they are unstoppable, they will marsh across the top of the continent, depending on affects of temperature , rain , floods , etc until they have conquered the lot. It also appears that they have a significant impact on the native wildlife, but eventually the cane toads seem to run out of food and their super fast breeding cycle slows down. Or as native animals adapt their numbers increase and they make a bigger dent in cane toads numbers. Maybe something has developed a taste for cane toad eggs?
Saw a documentary on tv that showed that the cane toads that were going west had grown longer legs and were able to cover more area faster, ie evolution. The quicker you get to new hunting grounds the more you eat, the more you breed etc.
Its bad for some natives like some quolls, etc, but once the natives ride out the initial assault, the impact from the cane toads drops off and they do recover.. Some species seem to do that better than others.
If I get a chance later I will go and have a google in particular see what the CSIRO has got going.
http://www.csiro.au/