And it can't be eradicated. But it can be made to practice birth control.

Poisoning, trapping, and shooting have been the traditional ways of culling the fox, but these are not enough to keep control over the numbers.

So rather than developing a means of killing foxes, CSIRO scientists decided to focus on preventing their birth, which is a more humane approach to controlling the fox population.

At first they attempted to identify a virus to deliver a vaccine to make the fox populations infertile, but then came up with a much better idea.

They developed a contraceptive vaccine to place inside blocks of bait that is irresistibly tasty to foxes.

"We are actually in the process of making a bait that will contain a contraceptive vaccine and this vaccine will actually trick the foxes' immune system into attacking its own eggs or sperm as though it was a foreign molecule and in this way preventing pregnancy."

Studying the behaviour of the fox is also important in controlling the population with contraception. For example there are dominant foxes which reproduce more than the others and some groups of foxes only meet occasionally to mate.

A similar birth control is also being developed for the European rabbit which currently costs Australia more than 600 million dollars annually in lost production.

The sterility bait is a totally new, humane way to control the fox population and other major pests around the country.