Molecular Ecology (2007) 16, 4919–4929 doi: 10.1111/j.1365-294X.2007.03553.x © 2007 The Authors Journal compilation © 2007 Blackwell Publishing Ltd Blackwell Publishing Ltd Genetic evidence that culling increases badger movement: implications for the spread of bovine tuberculosis LISA C. POPE,* ROGER K. BUTLIN,* GAVIN J. WILSON,† ROSIE WOODROFFE,‡ KRISTIEN ERVEN,* CHRIS M. CONYERS,† TANYA FRANKLIN,† RICHARD J. DELAHAY,† CHRIS L. CHEESEMAN† and TERRY BURKE* *Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK, †Central Science Laboratory, Sand Hutton, York, YO41 1LZ, UK, ‡Department of Wildlife, Fish and Conservation Biology, University of California, 1 Shields Avenue, Davis, CA 95616, USA Abstract The Eurasian badger (Meles meles) has been implicated in the transmission of bovine tuber- culosis (TB, caused by Mycobacterium bovis) to cattle. However, evidence suggests that attempts to reduce the spread of TB among cattle in Britain by culling badgers have mixed effects. A large-scale field experiment (the randomized badger culling trial, RBCT) showed that widespread proactive badger culling reduced the incidence of TB in cattle within culled areas but that TB incidence increased in adjoining areas. Additionally, localized reactive badger culling increased the incidence of TB in cattle. It has been suggested that culling-induced perturbation of badger social structure may increase individual move- ments and elevate the risk of disease transmission between badgers and cattle. Field studies support this hypothesis, by demonstrating increases in badger group ranges and the prevalence of TB infection in badgers following culling. However, more evidence on the effect of culling on badger movements is needed in order to predict the epidemiological consequences of this control strategy. Here, analysis of the genetic signatures of badger populations in the RBCT revealed increased dispersal following culling. While standard tests provided evidence for greater dispersal after culling, a novel method indicated that this was due to medium- and long-distance dispersal, in addition to previously reported increases in home-range size. Our results also indicated that, on average, badgers infected with M. bovis moved significantly farther than did uninfected badgers. A disease control strategy that included culling would need to take account of the potentially negative epidemiological consequences of increased badger dispersal. Keywords: dispersal, genetic population structure, Meles meles, microsatellite, sex bias, spatial autocorrelation Received 15 April 2007; revision received 18 July 2007; accepted 17 August 2007 Introduction Bovine tuberculosis (TB) has increased markedly in British cattle herds over the last 20 years and remains a significant economic and animal welfare problem (Krebs et al. 1997). Bovine TB has persisted in cattle in parts of the UK despite the implementation of control measures that have succeeded elsewhere. This persistence has been attributed to the exis- tence of a significant reservoir of infection in wild badgers (Meles meles) (Krebs et al. 1998), although cattle-to-cattle transmission is also important (Gilbert et al. 2005) and other wildlife hosts may also play a role (Delahay et al. in press). Control of TB in the past has included culling badgers, but the efficacy of this approach is variable. Following a review of TB control policy (Krebs et al. 1998), the impact of badger culling on TB incidence in cattle in Britain was assessed experimentally in the randomised badger culling trial (RBCT). This experiment aimed to measure the effect of reducing badger population density on rates of TB infection in cattle. The experimental design Correspondence: Prof. Terry Burke, Fax: +44 (0) 114 2220002; E-mail: t.a.burke@sheffield.ac.uk