A study led by researchers at international conservation charity ZSL (Zoological Society of London) and Imperial College London has found that culling drives badgers to roam 61% further afield - helping to explain why the practice, intended to reduce bovine TB transmission, can sometimes exacerbate the problem instead.
Published in the Journal of Applied Ecology today (Wednesday 9 October), the paper reveals that, after a population was culled, surviving badgers covered 61% more land each month than they had before the cull began, leading researchers to conclude that badgers explore new areas as individuals are removed from neighbouring groups and territories open up.
Badgers were also found to visit 45% more fields each month, and the odds of a badger visiting neighbouring territories each night increased 20-fold - potentially increasing the risk of TB transmission both to cattle and to other badgers. These changes were witnessed as soon as culling began, meaning even badgers that were killed may have first spread the infection over wider areas while management was being implemented.
Badgers however spent less time outside of their setts in culled areas - spending on average 91 minutes less per night out and about. ZSL scientists believe this could be linked to reduced competition and increased food availability as badgers are removed from the population.
The research group from ZSL's Institute of Zoology, and Imperial's MRC Centre for Global Infectious Disease Analysis, studied 67 badgers across 20 cattle farms in areas with and without farmer-led culling in Cornwall, collecting GPS-collar data between 2013 and 2017.
Lead author and ZSL-Imperial PhD researcher, Cally Ham explained: "Badgers spend a large proportion of the night foraging for food above-ground, and as culling reduces the size of the population, competition for food will also be reduced. We believe this accounts for the reduced activity levels, as well as bold individuals becoming obvious targets for culling and being quickly removed from the population.
"Because culling partly relies on shooting badgers moving around at night, the fact that badgers were active for fewer hours per night could actually be undermining culling efforts to further control badger numbers."
Professor Rosie Woodroffe at ZSL's Institute of Zoology, said: "As badger-to-cattle transmission is likely to occur through contamination of their shared environment, and TB bacteria can remain viable for long periods of time in the environment, the effects of increases in ranging behaviour could create a source of infection for several months - long after the individual badger has been culled. In contrast, studies have shown that vaccination prompts no changes in badgers' ranging behaviour."
Since the UK Government implemented the culling policy in 2011, ZSL scientists have been working to understand whether badger vaccination - a non-lethal alternative to culling - could be used to reduce the infection of TB in the UK's badger population, and so help control TB in cattle.
To find out more about ZSL's research into badger vaccination please visit: https://www.zsl.org/blogs/science/its-badger-culling-season-again-in-england
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Bovine tuberculosis (TB)
Bovine tuberculosis (TB) is the most important endemic livestock disease in the UK, with 5.8% of herds affected in 2018. Though the bacteria which cause bovine TB (Mycobacterium bovis) have been found in a variety of mammals, the European badger (Meles meles) has been identified as the predominant wildlife host in Britain. This has led to the widespread killing of badgers across the UK, after the UK Government announced the beginning of the culling policy in 2011. The government aims to reduce badger populations by at least 70% across a cull zone which currently covers nearly three-quarters of the southwest peninsula.
ZSL scientific event: Can badger vaccination help eradicate bovine TB?
8 October 2019, 6pm - 7.45pm
Free to attend, please email firstname.lastname@example.org to confirm your attendance as press.
For decades, conservationists, vets and farmers have been at loggerheads about the best way to manage bovine tuberculosis (bTB). This cattle disease, which can be a huge burden on farmers and farm businesses, also infects badgers. Badgers can pass the infection back to cattle, making it difficult to eradicate the disease. In England, the government's bTB policy encourages farmers to kill badgers in a series of coast-to-coast culling operations which already cover over half the land area of the South West Peninsula, with tens of thousands of badgers killed each year. However, a recent independent review advised the UK government to explore badger vaccination as an alternative to culling, and the Irish government is already moving from culling to vaccination. At this event, scientists, farmers and policymakers will review the evidence concerning the effectiveness, practicalities and cost of badger vaccination, to explore what role it might play in eradicating bTB from Great Britain.
For more information, visit: http://www.zsl.org/science/whats-on/can-badger-vaccination-help-eradicate-bovine-tb
ZSL (Zoological Society of London)
Founded in 1826, ZSL (Zoological Society of London) is an international scientific, conservation and educational charity whose mission is to promote and achieve the worldwide conservation of animals and their habitats. Our mission is realised through our ground-breaking science, our active conservation projects in more than 50 countries and our two Zoos, ZSL London Zoo and ZSL Whipsnade Zoo. For more information visit http://www.zsl.org
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Imperial College London
Imperial College London is one of the world's leading universities. The College's 17,000 students and 8,000 staff are expanding the frontiers of knowledge in science, medicine, engineering and business, and translating their discoveries into benefits for our society.
Imperial is the UK's most international university, according to Times Higher Education, with academic ties to more than 150 countries. Reuters named the College as the UK's most innovative university because of its exceptional entrepreneurial culture and ties to industry.
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Journal of Applied Ecology