No abstract

1. Culling wildlife as a form of disease management can have unexpected and sometimes counterproductive outcomes. In the UK, badgers Meles meles are culled in efforts to reduce badger-to-cattle transmission of Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). However, culling has previously been associated with both increased and decreased incidence of M. bovis infection in cattle.2. The adverse effects of culling have been linked to cull-induced changes in badger ranging, but such changes are not well-documented at the individual level. Using GPS-collars, we characterized individual badger behaviour within an area subjected to widespread industry-led culling, comparing it with the same area before culling and with three unculled areas.3. Culling was associated with a 61% increase (95% CI 27%-103%) in monthly home range size, a 39% increase (95% CI 28%-51%) in nightly maximum distance from the sett, and a 17% increase (95% CI 11%-24%) in displacement between successive GPS-collar locations recorded at 20-min intervals. Despite travelling further, we found a 91.2 min (95% CI 67.1-115.3 min) reduction in the nightly activity time of individual badgers associated with culling. These changes became apparent while culls were ongoing and persisted after culling ended. 4. Expanded ranging in culled areas was associated with individual badgers visiting 45% (95% CI 15%-80%) more fields each month, suggesting that surviving individuals had the opportunity to contact more cattle. Moreover, surviving badgers showed a 19.9-fold increase (95% CI 10.8-36.4-fold increase) in the odds of trespassing into neighbouring group territories, increasing opportunities for intergroup contact. 5. Synthesis and applications. Badger culling was associated with behavioural changes among surviving badgers which potentially increased opportunities for both badger-to-badger and badger-to-cattle transmission of Mycobacterium bovis. Furthermore, by reducing the time badgers spent active, culling may have reduced badgers' accessibility to shooters, potentially undermining subsequent population control efforts. Our results specifically illustrate the challenges posed by badger | 2391 Journal of Applied Ecology HAM et Al.

Summary Because biological systems are complex, management interventions occasionally have unintended adverse consequences. For example, attempts to control bovine tuberculosis (TB) by culling badgers Meles meles have, under some circumstances, inadvertently increased cattle TB risks. Such harmful effects occur because culling profoundly alters badger movement behaviour, increasing pathogen transmission both between badgers and from badgers to cattle. It has recently been suggested that another TB management tool, badger vaccination with Bacillus Calmette Guerin, might provoke similar behavioural changes and hence similar harmful effects for cattle. We therefore took advantage of an existing project, which monitored 54 GPS‐collared badgers across four study sites in southwest Britain, to explore whether vaccination, or live trapping to administer vaccine, influenced badger movement behaviour. We detected no significant effects of either vaccination or trapping on badgers’ monthly home range size, nightly distance travelled, or frequency of trespassing in neighbouring territories. The estimated effect of vaccination on badger home range size [2% reduction, 95% confidence interval (CI) 18% reduction – 17% increase] was statistically non‐significant, but significantly smaller than that associated with both widespread (180% increase, 95% CI 70–362% increase; P < 0·001) and localised badger culling (74% increase, 95% CI 4–191% increase; P = 0·038). Synthesis and applications. In contrast with culling, live trapping and vaccinating badgers did not measurably alter their movement behaviour, fuelling optimism that vaccination might contribute positively to cattle tuberculosis control. Our study illustrates how existing monitoring can be exploited to assess potentially adverse effects of wildlife management.

Diseases transmitted from wildlife to livestock or people may be managed more effectively if it is known where transmission occurs. In Britain, farm buildings have been proposed as important sites of Mycobacterium bovis transmission between wild badgers (Meles meles) and cattle, contributing to the maintenance of bovine tuberculosis (TB). Farmers are therefore advised to exclude badgers from buildings. We used Global Positioning System (GPS) collars and remote cameras to characterise badgers’ use of farm buildings at four TB-affected sites in southwestern Britain. Across 54 GPS-collared badgers, 99.8% of locations fell ≥3 m from farm buildings. Remote cameras deployed in feed stores recorded just 12 nights with badger visits among 3134 store nights of monitoring. GPS-collared badgers used space near farm buildings less than expected based on availability, significantly preferring land ≥100 m from buildings. There was no positive association between badgers’ use of farm buildings and the infection status of either badgers or cattle. Six GPS-collared badgers which regularly visited farm buildings all tested negative for M. bovis. Overall, test-positive badgers spent less time close to farm buildings than did test-negative animals. Badger visits to farm buildings were more frequent where badger population densities were high. Our findings suggest that, while buildings may offer important opportunities for M. bovis transmission between badgers and cattle, building use by badgers is not a prerequisite for such transmission. Identifying ways to minimise infectious contact between badgers and cattle away from buildings is therefore a management priority