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A problem of cunning tasmanian foxes or much less cunning innovation?

By Clive Marks - posted Tuesday, 25 September 2012

Foxes would bring disastrous ecological consequences for the island state of Tasmania. That's been stated so often that it is deserving of a fridge magnet.

While we should all be supportive of the intention of any effort that seeks to prevent foxes establishing in Tasmania, there is much more required than good intentions alone. After all, the road to hell is paved with them.

In the scientific equivalent of feeling the width and disregarding the quality, good intentions and programme names containing active verbs can sometimes seem good enough. However, callingsomething an 'eradication programme' is not the same as demonstrating that you have the potential to do just that.


The problem is that I still can't know if there is a free-living fox population in Tasmania or if there ever was. If a fox population is present, I can't know if it is being 'eradicated' either.

The devil, as always, is in the details.

Two known fox introductions, one in 1998 and another in 2001 stand as convincing evidence of 'free-living' foxes once existing in the Tasmanian environment in the recent past. In more than a decade since, the Tasmanian fox eradication programme has not managed to obtain conclusive direct evidence of a 'free-living' fox (ie. one that has perhaps been photographed by trail cameras; freshly killed by shooting; trapped; evidenced by fresh tracks or bait take; confirmed calling in the mating season or by locating a den, cub or a very recently dead carcass etc.).

Of course, the absence of evidence is not evidence of absence – granted.

Yet, given the Tasmanian government's claims of large-scale releases of up to 19 foxes prior to 2000 and thousands of public sightings and the investigations that followed, the dearth of convincing physical evidence has been surprising. Did the big fox release even happen as once claimed? Well, no one actually has presented any evidence for that either. Even the Tasmanian Police agree on that point.

Significantly, there is no evidence that even one 1080 bait has been taken by a fox; something regularly monitored on the mainland to the point of being a prosaic event. Instead, public sightings have been widely used to justify not only the start of the fox eradication programme but also its focus, the status of the assumed population and eradication success. Strangely, from 2003 fox sightings in Tasmania became progressively more common as the media campaign grew.


I'll be blunt. Reliance upon public sightings of foxes to target eradication efforts and to determine control effectiveness is pseudoscientific - and illogical. Public sightings are not scientific 'data' and should never be treated as such. They are unable to be replicated or controlled and without physical evidence located to corroborate them, they are totally useless. Otherwise the thylacine must also abound, not only in Tasmania, but also in mainland Australia where thousands of similar public sightings have been made over the decades. Accept public sightings, without corroboration, as a measure of a fox population, and you can bring the thylacine back from extinction with a similar piece of pseudoscience.

The Victoria government recently took a refreshing and commendably scientific approach to this very problem. Despite many sightings, dubious prints, stories and prey kills that many claim are proof of 'big cats' (pumas or panthers) in south-east Australia, scientists concluded that there just wasn't any reliable scientific data to suggest their existence was likely. The onus now remains squarely with those who make claims otherwise to find some – and that's how it should always be.

Thank goodness the Victorian government did not set about to eradicate big cats on the strength of public sightings, claims and dubious evidence.

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About the Author

Dr Clive A Marks is the director of Nocturnal Wildlife Research Pty Ltd and was the head of Vertebrate Pest Research in Victoria for over a decade. He has published widely on aspects of fox biology and control in independently peer-reviewed science journals.

Other articles by this Author

All articles by Clive Marks

Creative Commons LicenseThis work is licensed under a Creative Commons License.

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