The environment secretary’s explanation to parliament for the badger culls missing their target kills – that the animals “moved the goalposts” because their population numbers declined – has been dismissed by the UK’s leading badger experts.
Owen Paterson had told MPs last week that the reason for the decline was “screamingly obvious, badgers are wild animals that live in an environment in which their numbers are impacted by weather and disease” over the past year.
However, experts told the Guardian that other closely monitored badger populations in Gloucestershire and Oxfordshire had had no decline at all.
Scientists say the most likely explanation for the population drop in the cull zones was not natural causes but the illegal killing of badgers, and disruption of badger population surveys by protesters.
They have also warned that the problems with the cull risk making the issue of bovine tuberculosis in cattle worse rather than better.
The warning came on the day it emerged that the number of badgers shot by farmers in Gloucestershire was only 30% of the amount targeted.
Rosie Woodroffe, a professor and a key member of an earlier landmark 10-year study of badger culling, said: “It would be extraordinarily unusual for natural causes to change badger populations so rapidly, and indeed no such changes have been seen [elsewhere]. It’s extremely unlikely that ‘badgers moved the goalposts’. Indeed possible problems with the counting methods make it difficult to be sure whether the goalposts were ever in the same field.”
Another source, with deep knowledge of the subject, said badger populations had never been seen to crash by more than 20% in a year due to natural causes. “Never – it just doesn’t happen,” the source said.
Night-time shoots in the six-week pilot culls in Somerset and Gloucestershire were set a minimum quota of 70% of all badgers, but the target has been missed in both counties, with the Somerset cull only managing 59%. The Somerset cull has been granted a three-week extension and an extension is being considered for Gloucestershire.
But Labour’s shadow environment secretary, Maria Eagle, said the culls should be abandoned and accused Paterson of rigging the culls. “Instead of rigging the results of the trials by extending their length, risking spreading TB and infecting cattle, Owen Paterson should abandon this misguided approach.”
The badger populations at Woodchester Park, Gloucestershire, and Wytham Woods, Oxfordshire, are the most intensively studied in the world and have been monitored for decades. The Guardian understands that at the Woodchester Park project, just 30 miles from the cull zone and monitored by government scientists, badger populations are unchanged this year. “The population has flatlined for the last four to five years,” said a source.
The Animal Health and Veterinary Laboratories Agency, which runs the Woodchester Park project, provided the latest data to Paterson’s chief scientific adviser on 3 October but refused to make the information public. “Robust population estimates for 2013 can only be made once trapping in 2014 is complete,” said a spokesman.
Paterson told MPs on 10 October: “I cannot give the exact numbers at Woodchester Park, but in other areas there has been a significant reduction in badger numbers compared with this time last year.”
A Defra official has confirmed to the Guardian that the “other areas” Paterson was referring to were the pilot cull zones.
David Macdonald, a professor at Oxford University, who studied the Wytham Woods badgers for 25 years, said: “2013 is not over yet, but it is possible to compare 2013 and 2012 at this stage of the year.” In 2012, at this stage, 146 badgers had been counted, while in 2013 there were 143, he said. “Certainly it provides no evidence of change outside the normal inter-annual variation.”
The population estimates are vital because the earlier 10-year £50m trial of badger culling found that at least 70% of the badgers had to be killed to ensure bovine TB was curbed. If too few badgers were killed, then those escaping would spread TB further afield and actually increase herd infections.
Woodroffe has already called for the cull to be stopped She says it is a costly distraction from vaccination and stricter controls on cattle movements.
The uncertainties over population are a serious concern, said Macdonald. “The hope that the cull might deliver the marginal gain originally predicted would be greatly diminished by a lack of reliability of the numbers.” He said the pilot culls had been successful in at least one sense – in determining whether shooting free-running badgers for six weeks could deliver the 70% cull needed to prevent fleeing badgers spreading TB more widely: “The answer is no.”
Like Paterson, a senior Defra source failed to include illegal killing and interference with counting methods as possible explanations for the pre-cull population crash in an earlier briefing, saying only: “Possible factors include the facts of last winter’s weather, where there was significant flooding in some of these areas, food availability might well be an issue, disease may also be an issue and there are also issues around statistical error.”
Macdonald said: “When citing reasons for population variation such as weather, food availability and disease, an obvious test is to look at other populations to see if the trends are general. The general point is that a task that at the outset was very hard – counting badgers – could by these various sources of inaccuracy and uncertainty be made so much more difficult, that it would undermine one’s confidence in the figures.”
He added that illegal killing of badgers would be counter productive because it also would increase perturbation, which is when fleeing badgers spread TB more widely.
Allegations of the illegal killing of badgers have been reported, including suggestions of gassing in Somerset. Anti-cull protesters also claim to have interfered with government scientists efforts to estimate badger populations by removing hair from the traps used to obtain DNA samples.
The DNA technique was used in the spring and summer of 2013, with the latter survey producing the much lower population estimates.
Jay Tiernan, of the Stop the Cull campaign, said: “We had a lot more people out [in August] as they were getting drawn in ready for the cull starting – we had probably five times more than before. The August DNA sampling was the one we did the most disruption of.”
A Defra spokesman said: “Interference with the hair traps is unlikely to account for the drop in numbers. Fluctuations in numbers of wildlife populations occur for a range of complex reasons that it is difficult to assess. We are not speculating on the causes for the drop in the badger population.”
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