The Parable of the Rabbit Plague in Australia

To understand the rabbit plague ,we need to understand a very simple dynamic about the rabbit population. This little causal diagram describes it particularly well.

Rand F1

As the number of rabbits goes up, the number of births also go up. This is indicated by a S at the  end of the causal arrows.   Births and rabbits form a reinforcing or growth loop. The important thing to remember about rabbits is that they only die once ,but may produce hundreds of offspring. This is what leads to exponential growth in rabbit populations.

So when Farmer Brown came out to Australia from England, he wished to make Australia as much like mother England as possible. So he imported as much of the flora and fauna as possible, particularly rabbits when he released on his rural property.

Now life in Australia was particularly good for the rabbit. There were no natural predators  and there was abundant food on Farmer Brown’s farm. It wasn’t long before the rabbit population exploded and the rabbits began to make serious inroads into Farmer Brown’s pastures.

Then Farmer Brown had a brilliant idea that was linked to the idea of making Australia more like mother England: import foxes. This would have the advantage of curbing the rabbit population and allow  Farmer Brown, now a member of the landed gentry, to gallop about in funny clothes shouting Tally Ho.

The logic went like this:

Rand F 2

As the number of rabbits goes up, you increase the number of foxes (foxes up, rabbits up)  as the foxes go up, the deaths of rabbits go up and then the number of rabbits goes down (deaths up rabbits down: moving in the opposite direction).  This loop is what is known as a balancing loop. It is reflection of Farmer Brow’s policy of importing foxes. Policy loops are often designed to bring systems back into balance

Now this worked particularly well for a while and the foxes had a field day because rabbits was so fat and lazy they almost  stumbled into the jaws of the foxes.  But after a while, something began to worry Farmer Brown. He noticed that the foxes were beginning to attack his chooks.  So he redoubled his efforts at fox hunting.

Rand F4

This was another policy decision designed to bring the fox problem under control. And it was successful. As the fox hunting went up, the number of foxes declined. But unfortunately, as a number of foxes declined so did the number of rabbit deaths and the rabbit population increased once more.

The logic goes like this: as fox hunting goes up the number of foxes goes in the opposite direction, namely down. As the foxes go down, deaths  of rabbits go in the same direction as well down also. As the rabbit deaths go down, the rabbit population goes in the opposite direction namely up. So unfortunately, Farmer Brown’s fox hunting policy was completely counter intuitive in that it led to a renewed increase in the rabbit population.

Then Farmer Brown, who was now in State Parliament and Minister for Agriculture hadanother brilliant idea: poison the rabbits. This was done using a poison known as myxomatosis.

R and F5

The logic was that increases in the number of rabbits would lead to an increase amount of poisoning and this would increase rabbit deaths. It was wildly successful. Farmer Brown received his knighthood for his efforts in controlling the rabbit population.

But what Farmer Brown did not know was there was a limit to the success of the poisoning program. It killed off all the rabbits but two, a male and a female living out beyond Gapuwiyak. Two tough old bastards, who were myxomatosis resistant and extremely fertile.

rand F 6

The result of the poisoning was to produce genetic modifications in two rabbits  (it only needed to) and that led to the production of the Super Rabbit.

The first inkling that Farmer Brown had of this was, when one night as he was looking out over his pastoral spread he suddenly heard a heavy thump, thump, thump. As he turned round, he was shirt-fronted by a large furry steamroller.

When he stood up, what he saw filled him with terror. In the nearby paddock, the super rabbit was enjoying sexual congress with a kangaroo.

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