Badger culling 2015: where are we now?

For the ambitious civil servant, there must be no worse nightmare than a transfer to TB section. For decades, efforts to control bovine tuberculosis in Britain have been mired in uncertainty and controversy. It’s almost impossible to succeed, because the solution is guaranteed to infuriate somebody.

The TB problem is a genuine one. Frequent cattle testing keeps the disease more or less in check, but this testing places a financial and emotional strain on farmers which cannot and should not be ignored. Although most transmission to cattle comes from other cattle, badgers also help to maintain the disease. To many farmers, badger culling seems an obvious solution – but there are two major obstacles. First, badgers are among Britain’s most iconic species, protected by their own Act of Parliament, and beloved by many. Second, scientific evidence shows that badger culling must be all-or-nothing: virtually eradicating badgers from vast swathes of countryside would probably help to reduce cattle TB, but culls which are small-scale, patchy, inefficient or discontinuous have been found to increase TB rates in cattle. So, there can be no compromise: killing a few badgers may be more acceptable to the public, but it is likely to worsen the TB problem.

Male badger. Image (c) Seth Jackson
Male badger. Image (c) Seth Jackson

This last point may seem counter-intuitive; the underlying mechanism relates to the interplay between badger numbers and badger behaviour. Left undisturbed, family groups of badgers defend their territories against intruders: this behaviour also stops diseased badgers from ranging widely through the countryside. But culling disrupts this territorial system. Badgers which have evaded culling, and those which move in to exploit land vacated by culling, range more widely and mix more freely with one another, increasing the spread of disease. After culling there are fewer badgers, but each badger is more infectious to cattle because it is more likely to be infected, and because it ranges across more farms. Hence, only culls which greatly reduce badger density can be expected to reduce cattle TB. 

Public affection for badgers is an important argument against eradicating them, but it’s not the only obstacle. Because badgers are nocturnal and forage alone, killing large numbers of them requires considerable effort and cost. To try to reduce these costs, the government sought to replace cage-trapping (the method which had been used for decades) with “controlled shooting” of free-ranging badgers using high-powered rifles and shotguns. In 2013, it initiated a test of the safety, humaneness, and effectiveness of controlled shooting within two “pilot” culling areas in Somerset and Gloucestershire. It stated that: "If monitoring of the humaneness, effectiveness and safety indicates that controlled shooting is an acceptable culling technique, then and only then would this policy be rolled out more widely"

After two years of pilot culling, the government has indeed decided to "roll out" the approach to a new area in Dorset. So did the pilot culls show that culling was safe, humane, and effective?

Safety

“Controlled shooting” raised a number of safety concerns, not least because the culls attracted considerable public protest. The prospect of demonstrators clashing by night with armed marksmen in remote rural areas was worrying to some. Nevertheless, beyond some "near misses" recorded in Gloucestershire, and some unpleasant interactions which must have been frightening to all involved, the safety of the pilot culls has not turned out to be an issue of broad concern.

Humaneness

Rifles are widely used to shoot other wild mammals, but badgers’ low-slung shape and nocturnality make them a challenging target for a clean kill. The Independent Expert Panel which oversaw the first pilot culls noted that human victims of gunshot wounds are initially so shocked that they feel no serious pain for the first five minutes. The panel therefore reasoned that death within five minutes of shooting might be considered humane. Unfortunately, in the 2013 pilot culls between 7.4% and 22.8% of badgers were still alive five minutes after being shot. Efforts were made to improve humaneness when the pilot culls were repeated in 2014, but with little success: the equivalent figures were 4.1-18.6%. On this basis, the British Veterinary Association called for controlled shooting to be abandoned as a culling method. This advice was dismissed by the farming Minister, who stated simply that "we don’t agree". Controlled shooting was once again approved for use in 2015.

Particularly worrying is the use of shotguns to kill badgers. The Independent Expert Panel cautioned that it had received too few data from the 2013 culls to be able to assess the humaneness of free shooting with shotguns, and called for shotgun use to be either discontinued or rigorously monitored. The government initially committed to close monitoring, but subsequently chose not to allow the use of shotguns for free shooting in 2014. Although there is consequently no evidence of the humaneness (or otherwise) of killing free-ranging badgers with shotguns, this activity was licensed in 2015

Effectiveness

Because changes in cattle TB take years to emerge, the government chose to measure the effectiveness of the pilot culls as the reduction in badger population size that they achieved. This makes sense because, as explained above, killing too few badgers increases cattle TB rather than reducing it. The government aimed for licensees to reduce the density of resident badgers by at least 70%. In 2012, when the licensees felt unable to kill the required numbers of badgers, the Secretary of State delayed the culls, saying that: "It would have been quite wrong to go ahead when [licensees were] not confident of reaching the 70% target and could have made the position worse."

When the pilot culls took place in 2013, they conspicuously failed to kill the requisite number of badgers, taking just 37-51% in Somerset, and 43-56% in Gloucestershire. The annual culls were repeated in 2014, but there was no quantitative assessment of the population reduction achieved. However, simple calculations (detailed here) suggest that the aim of reducing badger numbers by “at least 70%” was once again missed by a mile. Nevertheless, the same aim was reiterated in 2015 when the government gave the go-ahead for a third year of culling. 

However, the small print associated with the cull licenses tells a different story. To try to make sure that enough badgers are killed, each licensee is given a minimum number of badgers which must be killed within a single six-week period each year. Setting these minimum cull numbers is difficult, because badger numbers are very uncertain. The situation can be likened to a short-sighted person competing in a high-jump competition without their spectacles. The bar to be jumped has a specific location in space, but to the short-sighted competitor it appears fuzzy, with a location known only approximately. Scientists represent such uncertainty using a “95% confidence interval”. For example, the 95% confidence interval around the pre-cull estimate of badger numbers in the Somerset cull zone was 1,876-2,584, meaning that there is a 95% probability that the true number of badgers was less than 2,584, but more than 1,876. The minimum numbers of badgers to be killed in 2015 were derived from this lower 95% confidence limit – an approach which would normally have only a 1 in 40 chance of reducing badger numbers by “at least 70%” as planned. In the high jump analogy, this is akin to a short-sighted athlete hoping to jump over the fuzzy bar he perceives by aiming for its lower margin. While there’s a small chance that he’ll clear the bar, crashing into it is much more likely.

Figures from the Gloucestershire cull zone show the craziness of this approach. Although the 2014 cull missed its minimum target by 341 badgers (274 killed, when the licence required 615), the minimum number to be killed in 2015 (265) is insufficient to make up the difference, even if it is (conservatively but improbably) assumed that neither immigration nor births occurred since the 2014 cull was completed.

The government described the choice of such low minimum numbers as "realistic" since earlier, higher, targets were not met.  They also described it as "precautionary". It is important to stress that this choice is by no means precautionary in the context of disease control because, as the previous Secretary of State agreed, killing too few badgers risks increasing TB risks for cattle.

Beyond the pilot culls

In setting up the pilot culls, the government stated that badger culling would be rolled out to new areas only if it was shown to be safe, humane, and effective. To justify this year’s rollout to Dorset it has ditched independent scrutiny, dismissed the veterinary profession’s views on animal welfare, and indulged in some statistical limbo-dancing to fix the figures on effectiveness. Its chutzpah would be comical, if it didn’t risk more dead cattle, more dead badgers, and more ruined farmers.

Badger vaccination project. Image (c) Seth Jackson
Badger caught as part of ZSL's vaccination project. Image (c) Seth Jackson.

But there’s more to come. The government has also announced a public consultation on further watering down the requirements for culling licences. Restrictions on the maximum cull duration, minimum cull area size, and minimum percentage of accessible land were all put in place to avoid making the cattle TB problem worse. Now the government considers these necessarily stringent criteria "unduly inflexible" and proposes to relax or abandon them. Mysteriously, it states that: "these proposals are not expected to materially affect the benefits of culling on levels of bTB in cattle", despite the wealth of scientific evidence to the contrary. You can read ZSL’s response to the public consultation here: PDF icon ZSL bTB consultation response September 2015 (106.66 KB).

Proponents of culling point to the crippling economic burden of TB control, demanding that something be done about it. But the government’s own cost-benefit analysis predicted that culling would not protect enough herds to be financially worthwhile. Since then, the culls have proven much less effective than anticipated (reducing the likely benefits), and much more costly, with each badger killed to date costing taxpayers around £7,000. Additional costs have been borne by farmers themselves.

Scientists are advised to present the evidence but to leave policy recommendations to others. So: the evidence suggests that licensed badger culling is inhumane and costly, with limited expected benefits for TB control and a realistic prospect of detrimental effects. This view is shared by many independent scientists, including the chairs of three successive committees advising government on the matter. Proposed changes to licence conditions are likely to further reduce the benefits of culling for farmers, and increase welfare costs for badgers. I will leave you to draw your own conclusions about how these statements should inform policy.

I started by describing the difficulties of advancing an effective TB control policy. But, in fact, progress is being made. After years of steady increase, cattle TB rates are starting to decline. This change is not related to badger culling; it almost certainly reflects improved cattle controls starting to take effect. This decline is especially marked in Wales, where cattle testing has been most stringent; recently, further tightening of cattle controls has been proposed for England. At the same time, improved understanding of how, where and when badgers and cattle come into contact – including findings emerging from my own research group – should eventually help farmers to improve biosecurity by discouraging badger-cattle contact. Badger vaccination is also a promising tool, although there needs to be a better evaluation of its impact on cattle TB. Vaccinating badgers is already cheaper than culling, and investigations are underway to further reduce costs, both by involving volunteers, and by developing an oral formulation which does not require capturing badgers. Before the pilot culls commenced, a team of scientists (myself included) warned publicly that: "badger culling risks becoming a costly distraction from nationwide TB control". It looks as though we may have been right.

Find out more about ZSL's badger cattle contact project and badger vaccination.

 

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