Image for Where has the evidence gone?

No new confirmed evidence of fox activity has been found in Tasmania since 24 March 2010. Does the recent absence of evidence confirm evidence of absence?

The short answer is no, or at least, not yet. From 2008 to 2010 the Fox Eradication Program ran a strategic carnivore scat survey across the State. It became colloquially known as the ‘Great Poo Hunt’ and collected a substantial number of fox scats including the most recent one found in the Forth area last year. It became clear from this and other monitoring activities that continued searching would likely locate further evidence but that this would not increase the knowledge about foxes in the State.

This view was supported by two independent reviews of the Program that were conducted in 2009. Indeed, it wasn’t the best use of resources to continue to repeat the effort when the focus should be on eradicating the animal leaving the scats.

‘The focus is now on eradicating the threat rather than chasing further evidence.’

The focus (under Stage 2 operations that commenced in 2010) is now on eradicating the threat rather than chasing further evidence that foxes are in Tasmania. The monitoring focus has shifted from state-wide, strategic activities to localised, post-bait monitoring behind baiting fronts. Two baiting fronts are now moving across Tasmania under this new approach and monitoring resources are being used to search areas where baiting has been completed. The lack of evidence found behind baiting fronts to date is a positive for Tasmania and provides some confidence that the eradication effort is delivering the desired outcomes. It is still early days for this approach and ongoing monitoring is occurring to ensure it is effective.

[Reference: Eradicate - the official newsletter of the Fox Eradication Program - Issue 4; Winter 2011]

Consider the following two statements:
1)    Fox scats are produced by foxes
2)    This fox scat was found in Tasmania

In the absence of any other information, the conclusion that the fox scat is from a fox living in Tasmania is a guaranteed outcome if both statements are true. Such arguments, in which the truth of the statement implies the truth of the conclusion, are called deductively valid. Such deductive arguments based on two simple premises nearly always have the flavour of certainty about them.

Two statements can be true and yet the conclusion linking both may be invalid. If you think a fox scat found in Tasmania is not from a fox living in Tasmania, but you still accept both premises, then you have an invalid conclusion.

The deductive conclusion up to 2010 has been: the evidence is here, so the foxes are here. [unsound arguments and an invalid conclusion] Now in 2011 reasoning is: we don’t look for evidence any more, we just eradicate the foxes leaving the scats. [unsound arguments and no conclusion]