Wednesday, July 25, 2007

Peturbation - update

Following on from our posting below where we explored Professor, Sir John Kreb's proposals for his trial in 1997, and the reality of what the ISG delivered, a dialogue on 'peturbation' and its effect of the ISG results ensued, the basics of which we post below.

We wondered why previous clearances had been so successful and the RBCT so dramatically the opposite. What was this so-called 'edge effect' of Bourne's trial and why was it not apparent in previous clearences - or if it was, why not a problem?

We were accused of naivity in 'ignoring the results of the trial', to which we replied:
Which trial?
This posting explored the protocol proposed by Professor, Sir John Krebs in 1997 for the latest effort by the ISG. It is quite clear from his recommendations that to avoid peturbation (and thus increased spread of disease), many things should be done and conversely, other things should not.
It is equally clear that these recommendations were not followed by the ISG in the current trial, with entirely predictable consequences.

Smaller, more targetted but intense clearances over a longer (than 8 nights) time frame would appear from past policies to have a far better effect as Professor Krebs explained in 1997. A policy which was supported by Professor Steven Harris in his

"alternative to the RBCT" which we explained in July 2004.

We pointed out that the The RBCT showed how NOT to carry out a cull, from information which was known already : not that it should not happen at all, a point with which our questioner agreed - with reservations.

You're right when you say that it showed how not to carry out a cull - an experiment isn't always there to show how to do something but also that something isn't the right thing to do. But you miss my point which is: more intense culling would not have prevented the perturbation which caused the rises in incidence that were seen. Therefore your constant harping about how they should have culled more intensively is completely irrelevant as it wouldn't have actually improved the result in terms of lower cattle incidence.

We had not missed the point at all, but it was a point with which we did not agree, for the following reasons:
The results from Thornbury, the 'Clean ring' strategy and Professor Harris' proposed alternative to the Krebs RBCT do not support your conclusion. And from our posting here, even Professor Krebs realised how not to do his trial.

You are saying that peturbation occurs if any or all of a group are removed, I think.
We agree that of course another group would gradually expand territory to fill that gap, but we also pointed out from a badger expert's extensive research, that the first dominant scent marker to define that new territory would prevent territorial scrapping and bite wounding.

We then explored what we have learned as cattle farmers about badger behaviour in this situation.

Is it possible that when an entire social group is removed then the next badgers moving quickly into the area may be diseased 'dispersers' from neighbouring groups? Is that why a more prolonged culling stratgy, even on a small scale worked? And after this, the inevitable recolonisation is from a healthier, more stable group?

In other words, it is not the first foray into an infected population (especially with cage traps) which is important, it the the second one which mops up dispersers and those missed the first time around? Thus to prevent the spread of disease, that second or even third clearance should be within a very short period of time and certainly not the years the ISG took.

We pointed out that past policies of large scale of intensive clearance (Thornbury) worked extremely well with "no other contemporaneous change identified that could have accounted for the reduction in [cattle] Tb incidence within the area” [Hansard 24thMarch 2004 Col 824W [157949]. The Thornbury clearance, (begun when cattle incidence reached 5.4 percent) was not so very long term either, starting in December 1975, and ending in August 1976. After which badgers were able to recolonise clean ground, their numbers recovering to pre cull levels, but the area remained clear of Tb in cattle for in excess of 10 years.

Smaller clearances in response to Tb breakdowns, which targetted setts (and groups) implicated in a farm or group of farms breakdown during the ‘clean ring’ strategy were also successful, and from contributers to the site who were involved, lasted about 6 / 8 weeks.

And we agreed with the questioner's point of leaving the social group intact, while querying the peturbation effect of this:

We do wonder if provided the group is left intact, or conversely removed completely the ‘peturbation’ effect is overstated? When a food source is available, Prof. Roper's research showed up to three groups sharing feed during night filming in Glos. cattle sheds. And we have told on this site of 84 badgers crossing a small field nightly, on their way to be served peanuts for the benefit of paying viewers in a Staffordshire wildlife park. That would be around 8 groups on Harris methodology, would it not?

CSL’s hand fed Woodchester badgers often make forays into adjacent territory: “Temporary and permanent dispersal from one group to another occurs regularly” Hansard: 17th March 2004. Col 274W [157988].

The point we were trying to make here is NOT to remove the strongest, leaving the sick, old and weak behind as the RBCT did – at least for its first 4 years. WLU operatives have commented on this site that after that the ISG did listen – a little bit – and refined trapping protocol accordingly, with better results.
Thus we cannot agree your conclusion that better culling would have made no difference to the results of the RBCT. That’s hypothetical and not born out by the examples above.

Experience has shown that even smaller clearances are successful if carried out thoroughly. And last years’ PCR trial from Warwick found about 64 per cent of the setts in the Glos. hotspots showed negative for Tb, so any movement of badgers from these would be without immediate risk to cattle, or to other badgers.

Our questioner thought we had made two opposing answers to badger clearances but we had not:

We have not altered tack at all on this site. We do not favour wipe out - of any species, just tuberculosis.

But we cannot see the sense in criticising the basis or conclusions of the RBCT, and then trying to cherry pick bits of it, while expecting government to ignore its less palatible proposals. In the interim and final ISG reports, Bourne intimated that a bigger cull with 'hard' boundaries would be more successful. It would, but the boundaries and scale would be so big as to be unworkable - in our opinion. That is not to say that some groups / politicians may not grab this as a possibility.

What they ignore is the ISG's seductive prediction of a drop in cattle Tb of 15 percent if more cattle measures are adopted, over and above preMT, now into its second year.

The only way this will happen is if gamma and more frequent testing (difficult if you are aleady doing it every 60 days) takes out 15 percent more cattle. How killing more cattle but faster can answer the problem, while leaving a reservoir behind in badgers, we explored in our post here.

And we are aware that any such proposal on badger control could inevitably have extra cattle controls bolted on, despite the past futile experience which we have described above: from past (bitter) experience, government have a nasty habit of dividing their agreement 'packages', prior to implementation.

We think what this boils down to, is to understand how badger ecology - away from the well drained, well fed population at Woodchester - operates, and use this to 'manage' a now widely infected population in areas of endemic tb. And for several years now, that is what the authors have tried to do (understand that is - it is government's responsibity to control bTb, not farmers.)

Cattle testing on a regular (annual) basis of course is part of this, but in isolation from clearing infection from wildlife reservoirs, it has been shown to be totally ineffective.

It is futile to repeat past mistakes; but we must learn from them, including the latest debacle and move on from strategies which proved succesful, using up to date technology as back up.

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